Troubleshooting the PowerSurvivor 40E

On page 24 of the Katadyn 40E Owner's Manual there is a flowchart to use when troubleshooting your 40E watermaker. Unfortunately, it's limited to a single page and there isn't much in the way of detailed information or comments. My purpose in this article is to augment the information given in that flowchart by providing some valuable details and tips I've learned the hard way over many years of troubleshooting PUR and Katadyn watermakers. In my discussion, I'll follow the flowchart, step by step, adding my comments as I go. To help you more quickly find a topic relevant to your situation, I've provided the following links which (except for the first two) mirror the first four boxes in the left-hand column of the flowchart.

General Comments On Troubleshooting:  Many cruisers never learn about how a piece of equipment works until it stops working and they have to fix it. The cruising life is also a bit different in that there is often no one else around with the technical knowledge and experience to fix things for you, no matter how much you'd be willing to pay. For example, if your Katadyn watermaker develops a problem while you're in Puerto Escondido, B.C.S., Mexico, you won't find a watermaker repair shop in the nearby town of Loreto. And getting the defective equipment to an official warranty repair shop is likely to be expensive, time-consuming, and highly unreliable, if it's even an option. The bottom line is: you're frequently on your own—if you can't fix it, it'll stay broken.

When you talk to long-time cruisers, people who've been sailing around remote locations for, say, ten to fifteen years or more, it's amazing to discover how much they know about diesel engines, generators, refrigeration, electrical devices, fiberglassing, woodworking, rigging, etc. Learning how things work and how to fix them is an unavoidable and well understood part of the lifestyle. On the other hand, very few of them first took off to go cruising knowing all there was to know about their equipment. For most it's pay-as-you-go, on-the-job training; indeed, it's part of the challenge of being a successful cruiser. New cruisers who are not willing or able to learn by getting their hands dirty are not likely to last more than a season or two. They'll take their boat back to the nearest marina that has a broker and put it up for sale.

Fortunately, you don't have to be a technical genius to troubleshoot and repair a Katadyn watermaker. You don't even need to know much about how it works. But you will need a few things:

You should always have the third item—at least a Repair Seal Kit for your watermaker—among the ship's spare parts. The kit not only has the parts that wear and will require periodic replacement; it also has many of the parts that are most likely to fail. Think of it the same way you would about having spare parts for your engine—fan belts, replacement impellers for the seawater pump, pencil zincs for the heat exchanger, etc.—Don't leave home without it!

I hope that the troubleshooting flowchart in the Owner's Manual and this more detailed article on troubleshooting tips will encourage you to try solving problems yourself. By steering you toward the more common problems and their solutions, they should also minimize the time you will need to find, understand, and fix most problems. You should note that the flowchart is organized in a very logical way, breaking down problems into four subcategories that correspond to the major functions of the watermaker.

There's simply no way I can cover every possible problem that could occur with your watermaker. Over my many years of troubleshooting, I've encountered some one-of-a-kind problems that just aren't likely to affect the typical owner/user. For example, there was a fellow in Mazatlan about ten years ago who brought his Model 35 watermaker to me, complaining that he had replaced the seals and now the watermaker would not fit together correctly. I fiddled with it for awhile and also couldn't get it to fit together properly. After perhaps an hour of continued frustration and head scratching, I realized the problem: he had installed a new poppet valve seat in its cavity and had not removed the old one.

Another story is about a fellow who had taken advantage of a special offer by Recovery Engineering to upgrade his Model 35 to a Model 40E. It required that the owner use the original drive unit and membrane. There were instructions on where to install the brine seal on the membrane and a new brine seal came with the upgrade kit; it goes on the other end of the membrane for the 40E. After completing the upgrade process, the owner tried running the watermaker. Every time, within a few seconds, it would trip the circuit breaker, as if there was an overload. Indeed, I discovered that there was an overload. While he had installed the new brine seal on the correct end of the old membrane from his Model 35 unit, he had failed to remove the original brine seal at the other end of the membrane. As a result, no water could flow through the watermaker—it was deadheaded, which caused the drive motor to stall and, very soon, the circuit breaker to trip from excessive electrical current.

By using the flowchart, this article, and a modicum of patience and logical thinking, you should be able to diagnose and repair about 90% of the problems that are likely to occur over the life of your watermaker. The other 10% may require a return to the factory or a warranty repair center. When you think about it, those are really pretty good odds for a piece of technical equipment—being able to fix it yourself nine out of ten times! If you get stuck, you can always drop me an email at Describe the problem and its history, and I may be able to give you some special advice that will help. Good luck!

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Some Tools of the Trade:  A TDS (Total Dissolved Solids) meter is right at the top of the list of optional equipment any serious watermaker owner should consider purchasing. It adds the ability to do quantitative analysis in addition to mere qualitative testing by tasting the product water. Tasting product water to test for acceptable quality is usually adequate for normal day-to-day use, but there are times when quantitative results are needed. For example, the difference between 250 ppm (parts per million) of contaminants and 700 ppm product water would be very difficult for most people to detect using only the taste of the water. Yet, those two readings represent, respectively, what I would expect from a brand new membrane and one that should be considered for replacement (all other factors being equal). In fact, I maintain that it is impossible to accurately monitor the history of a watermaker's performance or the actual quality of product water without a TDS meter. If you haven't already, you should read my comments about TDS meters in "What does a TDS meter tell about product water?" in the FAQs page of this website (See the navigation bar at the top of the page.)

Basically, tasting provides only a very gross indicator—a "go/no-go" test—of product water quality. For accurate and useful evaluation and monitoring of your system, a TDS meter is a must. Katadyn sells a high quality TDS meter, and they can be found for sale on the internet. When deciding what to purchase, be wary of inexpensive Chinese meters that claim to measure all the possible contaminants in your water. No TDS meter does that! It's a complete scam and, if you believe it, you're likely to be found dead someday from some terrible tropical disease, with a surprised look on your face. I'll have more to say about how to use a TDS meter in the section of this article, "Is product water quantity & quality normal?"

Another tool I've found indispensable for troubleshooting Katadyn watermakers is a magnifying glass or loupe. A 10X is adequate. I prefer a loupe and use it for careful examination of o-rings and seals. There have been many times that magnification has revealed a split or defect in a seal that was simply not visible to the naked eye. Everyone should have one—they have a million and one uses!

I suspect that every cruiser has a reasonably complete set of average tools aboard. In fact, the number of more specialized tools on board seems to grow in proportion to the number of years spent cruising. After thirty-one years living on a boat, I accumulated four tool boxes with such things as a refrigerant leak sniffer and gauge set, snap ring pliers, portable butane soldering irons, a variety of three-arm wheel pullers, a rigging tension gauge, etc. I list the tools that are needed to work on a Model 40E watermaker in the Repairs Video. They are mostly things you should already have on hand.

You will need a voltmeter to do the electrical troubleshooting. Nothing fancy, sophisticated or expensive is required. We won't be testing extremely high impedance oscillator circuits or anything like that. We'll only need to be looking at the very primitive data available in a simple shipboard 12VDC system. Therefore, just about any voltage testing device you can buy will be adequate for our purposes here. You can probably find something for under ten dollars at Radio Shack. Actually, I would be surprised to find any cruising boat that did not already have some kind of volt-ohm meter. If, on the other hand, you don't have such a device, you might want to consider spending a few extra dollars and getting a more generally useful piece of test equipment. For example, you might even want to splurge and spend thirty or forty dollars to get a digital meter that can test impedance and resistance, diodes (with an audible indicator), reasonable amounts of current (ammeter functions), with an assortment of test leads, and so forth. After all, there are many electrical/electronic devices on the average cruising vessel nowadays, some of which will require more functionality from your meter than is required for our simple watermaker tests. Just a suggestion.

Depending on the kind of problem you're investigating, you may need a watch, preferably with a stopwatch function, and some graduated/calibrated containers for collecting and measuring reject water flow and product water output. Comparing the amount of seawater throughput to the quantity and quality of product water output can tell you a lot about what's happening in your watermaker. Basically, the quality of product water is directly proportional to the speed of seawater flow across the membrane surfaces. If for any reason the seawater flow through the watermaker is slowed down, the quality of product water will be reduced.

Last in my list of special tools—but by no means least—is my custom-made "bypass rig." This is nothing more than a pair of 7/16" reinforced plastic hoses, 4-5 ft. long. (If you followed my advice at the end of the Installation article and installed your system from the get-go with 1/2" hoses and fittings, then of course you would want to use 1/2" hose for your custom bypass rig). This bypass rig is used by attaching one end of the two hoses to the intake and reject hose barbs of the watermaker and then leading the other ends into a bucket of clean seawater. The purpose is to be able to run the watermaker directly from the bucket of seawater, bypassing the entire seawater intake system (e.g., thruhull, seacock, strainer, booster pump, hose runs and prefilter).

I use my custom bypass rig more often than any other troubleshooting device. It allows me to isolate the watermaker pump itself from the entire intake plumbing system. This is extremely valuable for isolating a problem to either the watermaker or the intake plumbing. Many problems that seem to be caused by a defective pump are actually caused by air ingress or cavitation in the intake system. The bypass rig quickly indicates which area we should be troubleshooting. (It's also useful for making super-grade battery water—just fill up a bucket with product water and use the bypass rig to run the product water through the watermaker a second time. It's actually as good or better than the distilled water you can buy in a store)

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Electrical Supply Problems:   The first (upper left) box in the troubleshooting flowchart was intended to help you diagnose problems with the electrical power supply to the watermaker. You don't have to be an electrical engineer to do effective troubleshooting in this area. The number of things that are likely to go wrong here are relatively few and fairly easy to diagnose. If you consulted the flowchart for your problem and you wound up here, I'll assume you turned on the switch or circuit breaker that was expected to start your watermaker running, and nothing happened—that is, the watermaker didn't run.

Let me be brutally honest. It's hard to be a modern cruiser without at least a basic knowledge of electrical theory, especially Ohm's Law. If you draw a blank in this subject, please stop for a few minutes and read the section in my Watermaker Book entitled "Some Basic Electrical Concepts" beginning on Pg. 14. It just covers the bare minimum you should know about electrical theory, and you'll find the information useful time and again for troubleshooting many other problems down the road.

Step #1: So, you turned on the switch or circuit breaker for the watermaker circuit and the watermaker didn't run. This is a great opportunity to apply some logic to a problem. In this case, what we want to know is whether or not 12VDC electrical voltage is being applied to the electrical motor in the drive unit of the watermaker. (Of course, if you have a unit that runs on 24VDC, you'll be looking for 24VDC at the motor).

First, check for the most obvious things, such as:

  1. Is the main battery switch in an On position? This is the (usually) large switch that typically has at least four positions, labeled Off, 1, Both, and 2 (or something similar). This switch supplies power to your circuit breaker panel (or your switch/fuse panel), where the power gets divided up and distributed to the various 12V devices on your boat. If this switch is off, none of your other ship's 12V devices should be working (e.g., cabin lights, VHF radio, radar, or anything else with a label on your 12V distribution panel). If you check, and find the switch is Off, turn it on and test your watermaker again. If the switch is found to be On, try operating one of the other devices controlled by the switches on your distribution panel; e.g., the VHF radio. If that device works, you can reasonably assume that power is at least getting from the batteries, through the master switch, and onto the distribution panel buss. In that case, we can eliminate the switch as a cause of the problem. Of course, if you found the switch in an Off position and turned it on, and then the watermaker started working normally, your troubleshooting efforts are over. Wouldn't it be nice if all problems were that easy to solve?
  2. Is the circuit breaker or switch for the watermaker at the distribution panel switched On? If you already turned it on, check again. Perhaps you turned on the wrong breaker by mistake. The most likely culprits here would be the nearest breakers for other devices, like the ones just above or below the watermaker circuit breaker
  3. Are your batteries sufficiently charged up? You should realize that the watermaker drive motor will at least run slowly, even if the battery voltage is quite low (e.g., 8-9 volts or less). It's not a good thing to do and is hard on the motor, and the quantity and quality of product water produced will be very bad. In other words, the batteries would have to be almost completely discharged for the watermaker drive motor to not run at all. This is easy to test for quickly by turning on some other devices to see if they fail to work too. Your cabin lights can be a useful indicator here: if you turn them on and there is no light, or only a faint glow, your batteries are seriously discharged

O.K., I know that these seem to be trivial steps in our troubleshooting process but, remember, we're trying to be logical here, and that requires that we double-check all possibilities in an orderly manner. Besides, think how foolish you'd feel if you spent a whole afternoon tearing down your watermaker, only to discover around cocktail hour that the main house battery switch had been off all the time.

Step #2: At this point we've confirmed that the batteries are in a reasonably charged state, the master battery switch is On, the circuit breaker for the watermaker is On, and the watermaker still isn't running. The next logical step would be to determine if 12V is actually getting to the drive motor. This is easy to do if you were wise enough to add a terminal strip near the watermaker when you installed it. Use your voltmeter to test the voltage between the two terminals where the wires from the drive motor are connected. I'll discuss how to interpret the results in just a moment.

If you were lazy and used butt connectors to splice the power supply leads to the motor leads, you have a more difficult challenge ahead of you. There are four things you can try, none of which I consider good practice:

  1. You can try to slide the test probes from your voltmeter into the butt connectors and hope that you are able to make contact with the crimped metal or ferrule inside. Doing this successfully usually depends on what type of tip is on the end of your test probes. If you get a 12V reading, you're home free, and can consider your effort a success. If you don't get any reading, you won't know whether (1) there isn't any voltage there to measure or (2) there's voltage there, but your probes aren't able to make contact with the crimped wires in order to read the voltage. In the latter case, you should try one of the following techniques to get a useful voltage test.
  2. If your voltmeter came with a pair of insulation-piercing probes (probes with thin, needle-like tips that can easily pierce wire insulation), you can punch them into the two leads coming from the motor and test for 12V voltage. Unless you spent a bit more for your voltmeter, you're not likely to have such probes. Radio Shack sells a nice kit of test leads with an assortment of different probe ends, including insulation-piercing and alligator clips. They're very handy.
  3. You can use a sharp knife or packing knife to carefully cut a short slice of the insulation away from one side of the wire, to expose enough copper wire strands to use with your test leads. Be careful when you do this. What is required is a very shallow cut which exposes no more copper than necessary. Avoid cuts steep enough that they cut into the copper itself. When you are finished, a small dab of a "liquid insulator" compound to cover the cut is a good idea.
  4. Finally, you can simply cut the wires and then reterminate them. I actually think this is the best solution if you then install a terminal strip instead of new butt connectors.

Step #3: Now we need to interpret the results of the voltage test. There are three possibilities and we'll discuss what each of them implies in some detail:

  1. No Voltage Present: This is the simplest situation to diagnose. We can immediately conclude that the problem is not the watermaker. Knowing that any electrical circuit must be "complete" to operate (i.e., no breaks anywhere in the continuity of the circuit) we can assume that there is a break somewhere in the wiring or at some device that is inline. Since we have already checked that the master battery switch is On and is supplying power to the 12V distribution panel, we need to check everything between the panel and the watermaker leads. There are a couple of possible locations for the break that we will want to check:

    • Check the circuit breaker or switch/fuse: Although the circuit breaker is in the On position, it may not be working. Get behind the circuit breaker panel and use your voltmeter to test for voltage between the two terminals on the watermaker circuit breaker while the circuit breaker is in the On position. There should be no (or perhaps a few millivolts) voltage across these terminals. If you measure any substantial voltage across the circuit breaker contacts, that circuit breaker is bad. To confirm this, you can try temporarily disconnecting the watermaker lead from its circuit breaker and attaching it to another breaker of similar or larger amperage rating that is known to be working fine. If the watermaker then runs, you've found your problem. Replace the circuit breaker.

      If you have switch/fuse combinations instead of circuit breakers, the troubleshooting process is similar. A first step would be to remove and examine the fuse itself. You should be able to see a continuous metal strip between the two ends of the fuse. A blown fuse is usually pretty obvious, even if you're not an experienced technician. Instead of a strip of metal from one end of the fuse to the other, you're likely to see little balls of splattered metal and definitely no metal connection between the two ends of the fuse. If the fuse is not made of glass and the inside is not visible, use the ohmmeter function of your voltmeter to check for continuity.

      Keep in mind that the switch could be the failure point. Using a known good fuse, test the switch the same way you would have tested a circuit breaker; with a good fuse installed, turn the switch to its On position and test for voltage across the switch/fuse combination. If the switch and fuse are both good, there should be no voltage across them. If there is voltage, test the switch and the fuse holder individually in the same way to determine which has failed.
    • Check the wiring runs to the watermaker: What you'll be looking for are any breaks in the wiring itself (not very common) or any problems at terminal strips or junction boxes that might be in the circuit path. A terminal strip that has been exposed to seawater can deteriorate badly in a relatively short period of time. However, unless the watermaker has not been turned on for a long time (perhaps several months) a corroded terminal or junction point is not likely to fail suddenly. It's much more likely to cause less drastic problems over a longer period of time, such as low voltage and intermittent operation. Make sure to check negative (or "ground") wiring also, especially if there are any junctions or terminal strips inline.
  2. 12VDC Voltage Present: If you read a full 12VDC (or something close) across the terminals feeding the watermaker drive motor, there are only a few things that could be causing the problem.
    • Motor brushes not making contact: I've had this happen on one of my own watermakers. If you find 12VDC available at the terminals for your drive motor, but the drive isn't running and the circuit breaker for the watermaker is not tripping off, the indication is that power is available to the watermaker, but no current is flowing through the watermaker's motor. This can be caused by one of the motor brushes being stuck a slight distance away from the motor's commutator. In this case, first try applying a few sharp raps against the motor housing with a screwdriver handle or similar tool, close to the end containing the brushes (i.e., the end farthest away from the gearbox).

      If that doesn't work, and the brushes are accessible on your drive motor, try removing the brush caps and examining the brushes. If you polish the wider flat side of the brushes on a soft cloth to remove a slight amount of the carbon, and then reinstall the brushes, you may find that your problem has been solved.

      Over the years, there have been several different electric motors used in the drive units of PUR and Katadyn watermakers. Some had accessible brushes via plastic caps that could be easily unscrewed, while others had no such access points at all. In the latter case, one would only be able to get at the brushes by opening up the motor itself, which is a much more complicated process. If you have the problem symptoms under discussion here, your motor does not have easily accessible brushes, and you do not consider yourself competent to disassemble and reassemble a DC electric motor, I recommend you take the motor/gearbox assembly to a local professional for servicing. Amazingly, there are many very competent electric motor professionals in all third world countries. They usually do excellent work at quite reasonable fees. You might want to check on your local VHF radio net for references.
    • The drive motor has failed: If you're sure that 12VDC is being supplied to the drive motor and the motor won't run, it is likely that the motor has developed a defect, probably an open circuit somewhere in the internal wiring. A short circuit fault in the motor would normally draw excessive current and trip the circuit breaker (or blow the fuse). Unless you're competent to repair electric motors, you can either seek help from a local shop specializing in electric motor repair, or you can return the drive to Katadyn, if that is practical.
  3. Low or Fluctuating 12VDC Voltage Present: It is possible to have some voltage present at the motor terminals but the motor still doesn't run. This would be the case if, for some reason, not enough power is being delivered to the motor. Normally, this would cause a rather low voltage reading (e.g., 6-7 volts) and the reading might fluctuate. If you are certain that the batteries are well charged, then it would seem that a substantial amount of the battery voltage is being dropped somewhere else in the circuit instead of across the motor. This could be caused by a loose or badly corroded terminal or connection, or a failing component, such as a circuit breaker that has not quite failed 100%. Trace the wiring and visually inspect for loose connections and/or corrosion. Again, use the previously mentioned technique to detect voltage drops across the circuit breaker or switch/fuse device when the switch is in the On position. In the case of a low voltage reading at the motor terminals, the problem is not likely to be the motor, as the indication then would be a partial short in the motor itself, which should draw excessive current and trip the circuit breaker.

A final failure mode is a mechanical failure of the motor or drive unit, which has caused the motor to stall. In most cases this should cause excessive current and the circuit breaker (or fuse) will open. However, if you detect normal 12VDC at the motor terminals and the drive is not running, there's one last thing you can try. Turn off the power to the watermaker and remove the coupling pin that connects the drive shaft to the pump piston. Then try running the motor again. If it now moves normally without a load, there is likely a problem with the motor or the gearbox and it will require servicing by a professional or the factory. It is also possible that the pump itself is binding and creating too much resistance for the drive to operate against (although, as already mentioned, this should cause the circuit protective device to trip off). Before you go to the trouble and expense of seeking out a professional or the factory, you can try disassembling the pump, checking all seals and internal parts, and installing a Repair Seal Kit. Fortunately, this kind of fault is extremely rare.

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Is there reject brine water flow?  For the watermaker to work properly, there must be an adequate supply of seawater flowing through the pump and membrane. Nominally, there should be approximately 15 gallons of seawater flowing through the watermaker every hour. Ninety percent of this water continues on through the watermaker and is discharged as "reject brine water." The remaining ten percent is what gets pressed through the membrane and appears as product water.

When measuring the thruflow of seawater through your watermaker, look for gross anomalies. Thruflow up to 15-20% less than nominal is not uncommon, especially if the ship's batteries are not fully charged. Always evaluate this parameter with a grain of salt. Keep in mind that advertised "nominal" performance values for many types of equipment are actually "optimum" values, which look better on a spec sheet. In my experience, for example, product water output of 1.1-1.3 gal./hr. for a Model 40E is more realistic under most real-world conditions. The published specifications were probably obtained under optimal conditions; e.g., zero flow resistance in the intake system and maximum battery voltage (perhaps 13.8VDC).

The basic mechanism that implements this thruflow is quite simple. The pump was designed as a positive displacement pump, consisting of an intake poppet valve, a reciprocating piston moving in a cylinder, and a reject (or output) poppet valve. It's a very simple arrangement and there are only a couple of ways it is likely to fail.

The first failure mode is what I call "catastrophic failure." In this case, there is no or very little seawater thruflow at all. This condition is quite easy to detect. While the watermaker is running, observe the reject water thruhull. Is water coming out? If not, then do a quick check of some of the more obvious causes:

  1. Check the seacock at the intake thruhull to be sure it's open

  2. If you have a booster pump installed, check to make sure it's primed and there is seawater flowing through it

  3. Check any other locations where a seacock or valve has been installed in the intake line

  4. Finally, check the position of the three-way valve at the prefilter to make sure it's in its normal run position and not turned to the alternate intake line and strainer

  5. Check the seacock at the thruhull where reject water exits. Is it open?

If all these locations check out O.K., there is one more step you can do to isolate the problem: use your "bypass rig" hoses to bypass the intake system altogether. Attach one of your bypass rig hoses to the intake hose barb on the watermaker and the other to the reject hose barb. Put the other ends of both hoses into a bucket of clean seawater. Turn on the watermaker. Does seawater flow through the pump now? If it does, then the prior lack of thruflow is probably due to a still undetected restriction somewhere in the intake system. Start looking for a section of hose that has collapsed flat (usually at a sharp bend) or a booster pump that isn't priming properly.

If, on the other hand, there is still no thruflow, you need to take a closer look at the pump itself. In this case, the most likely cause would be a failure of one of the poppet valve components. Disassemble the pump (see my Repairs Video for detailed instructions on how to do this) and an o-ring on each poppet valve and inspect the o-rings carefully with a magnifier for defects or damage. Look for a broken poppet valve spring. Also look carefully around the valve locations for any pieces of flotsam that may be interfering with their proper action. You would think that the prefilter would prevent any foreign material from entering the pump. However, on several occasions, I've found such things as small bits of plastic or o-ring material, bits of teflon tape, etc., that have been preventing a poppet valve from seating completely. Clean and lubricate all parts and replace any failed components, as needed.

I have a few tips about poppet valve failures that I've encountered in the field. First, concerning the poppet valve itself, there have been two types of problems I've occasionally run into. The most common (but not frequent) is a defect in the o-ring on the poppet itself, which causes it not to seal, or to only seal partially. This kind of defect can usually be spotted by closely examining the o-ring with a magnifying glass. A related problem is an o-ring that is simply missing. In this case, it is likely it failed at some point and was pumped downstream and possibly out of the watermaker altogether. If you encounter such a situation with a missing o-ring, disassemble the watermaker and look for any remnants that may still be lurking, especially if the missing o-ring was from the intake poppet valve. If parts of the damaged o-ring are still inside the pump, they could possibly cause more trouble later, and should be found and removed. Secondly, a less common problem is damage or failure of the plastic poppet itself. This, again, is easy to detect with a magnifying glass. Replace the defective poppet (replacements are in the Repair Seal Kit) and reassemble the watermaker.

The other failure mode relating to the poppet valves is failure of the valve spring. In the very early Model 35 and Model 80-II manufactured by Recovery Engineering, broken poppet valve springs were a relatively common occurrence. According to the factory, the cause was the stainless steel alloy used for the springs. It had been specified by the military for the manufacture of the early hand-operated Survivor 35 under military contract. After it was discovered that the specified alloy developed a history of early failure, the alloy was changed, and there have been virtually no spring failures since that early date. My own experience confirms that fact. I have run across very few spring failures within the last ten years or so. It appears to me that the alloy now being used for the springs is robust and seldom subject to failure.

Finally, keep in mind that it is sometimes possible for the watermaker to have seawater thruflow and produce product water even with a broken poppet valve spring. In this case, taking an actual measurement of the amount of thruflow and testing the quantity and quality of the product water will usually reveal substandard performance.

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Is product water quantity & quality normal?  These are the most difficult problems to troubleshoot, for several reasons:

Let's first review a few basic reverse osmosis concepts that are helpful in understanding and troubleshooting the watermaker:

Concept #1: Because of the nature of the chemistry and physics involved in the reverse osmosis process, product water quantity and quality usually rise and fall together. That is, as the quantity goes up, the ppm count should go down (i.e., the quality goes "up," or improves). It is also a fact that the quantity and quality of product water gets better in proportion to the quantity of seawater passing over the membrane surface in a given amount of time.

Concept #2: Anything that reduces the normal internal operating pressure of the pump will also reduce the quantity of seawater flowing across the membrane and, therefore, reduce the Q&Q of product water.

Concept #3: The membrane is not a perfect device. It should only be expected to reject a certain proportion, or percentage, of the salts in the intake seawater. Given the typical salt rejection ratio of a new membrane of about 98% (or better), we should understand that the ppm count for intake seawater that is highly saline will be higher than the ppm count for intake water that is less saline. The effectiveness of a membrane can be expected to gradually deteriorate over time.

With these important concepts in hand, I think the most practical approach to troubleshooting problems of product water quantity and quality is to look at the issue from two different perspectives. First, we'll break down the measured performance of the watermaker into three ranges of ppm counts: 0-500, 500-1200, and higher than 1200. To accurately measure within the first two ranges (i.e., 0-1200 ppm), a TDS meter will be required. The third range can usually be detected by taste. Our second perspective will be to then look at the important parts of the system and discuss the most common types of problems and failures, and their causes, within each quality range. In the following discussions, take all of my ppm estimates with a large grain of salt. Realize that, depending on battery voltage, water salinity and temperature, membrane condition, and other factors, the estimates I mention could easily vary by as much as 100-200 ppm!

Range #1: 0-500 ppm This is the range to be expected from a watermaker in good condition with a good membrane installed and operating under normal conditions at a reasonable 12VDC voltage (e.g., 12.0-14.0 VDC). I would consider any product water in this range to be "good and acceptable." Here are some observations about operations within this range:

Range #2: 500-1200 ppm: As your membrane ages with normal use, the ppm count of your product water should increase very gradually, eventually passing the 500 ppm level. This is a natural process, of course, but the only way to monitor it accurately is to use a TDS meter on a regular basis.

What's even more interesting from a troubleshooting point of view is that, if the membrane is known to be good, this range of readings can reveal problems in the operation of the watermaker. Although you won't be able to determine the ppm count of your product water if you don't have a TDS meter, you can use another indicator that works almost as well: the output volume of product water. If you recall Concept #1 above, you should realize that you can measure this closely related parameter without sophisticated instruments, and it will usually tell you enough to let you know if you have a problem.

It's a good idea to periodically measure the volume of product water your watermaker produces. It really doesn't take too long. Use a watch or other timepiece and a small container that is graduated or of known volume to collect a timed sample of product water. Use a little grade school arithmetic to translate your readings to gal./hr or liters/hr, whichever you are most comfortable with. Note the DC voltage at the motor terminals while collecting your sample and write these observations down for future reference. At a minimum, you should do this shortly after the watermaker is first installed, if only to have an initial benchmark for later troubleshooting.

Actually, if you run your watermaker frequently on a regular schedule, before too long you should develop a "sixth sense" about how your watermaker is working and how much time it takes to make a given quantity of product water. You'll be able to sense any gross changes in the output level. Whether you rely on your sixth sense, a TDS meter, or output volume measurements, once you've confirmed that product water volume is significantly less than normal, you need to find out why. The following is a list of some various causes of low (or no) output volume and high ppm counts for product water that I've encountered over the years. Keep in mind that checking for air ingress or cavitation only makes sense if you've already confirmed that the watermaker drive is operating normally and there is reasonable thruflow of seawater. I recommend that you also check product water Q&Q while running the watermaker direct from a bucket of clean seawater, using your bypass hose rig. If it runs fine under those conditions, but problems occur when it is plumbed into your normal installation, cavitation or air ingress in the intake system is strongly indicated.

Range #3: Greater than 1200 ppm: If the ppm count passes 1000, the product water begins to take on a slightly but distinctly "salty" or contaminated taste. I can detect it at about 1000 ppm. My wife can taste a strangeness at a much lower ppm count, around 600-700. I think almost anybody could detect the "impure" taste by 1200 ppm. But I have an anecdote that applies here. There was a couple on a cruising boat who enjoyed making coffee every morning, using water produced by their watermaker. One morning, they invited another cruiser over for a cup of coffee. After he was served his cup, he took one sip and abruptly spit it out. Surprised, he asked them, "Why do you make your coffee with saltwater?" What had happened was that their watermaker had failed very slowly over a long period of time. They, of course, had also very gradually gotten used to the taste and weren't at all aware that there was a problem until they served coffee to a guest. The moral: there's no substitute for a TDS meter.

In any event, if your ppm count for your product water gets above 1200, you're likely to realize that something is seriously wrong, even without a TDS meter. Product water output volume will probably be greatly reduced, although this may not be the case if the problem has been caused by chemical damage to the membrane. Certain kinds of chemical damage may dramatically increase the "porosity" of the membrane and product water volume may actually increase as the quality goes down.

This kind of extreme ppm count can also happen rather suddenly, due to a catastrophic failure of some part of the watermaker. You should consider all of the possible causes listed under the 500-1200 ppm discussion. The good news is that, with failure that acute, the problem is probably going to be easy to find. The bad news is that it is probably going to require, at a minimum, the purchase of a new membrane and/or a dismounting and complete disassembly of the watermaker. Good Luck.

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Does it run without seawater leaks?  It is quite possible that the watermaker can develop a seawater leak and still produce a normal quantity and quality of product water. This is especially true of leaks originating at the piston shaft. However, the watermaker should not leak at all!  This may seem a little confusing to some owners, as the original PUR Owner's Manual indicated that the unit might develop a slight leak. If a leak develops, find it and fix it. There are only two common causes of leaks in the area of the piston shaft: (1) a damaged or defective piston shaft and (2) damaged or worn piston shaft seals.

If you detect a leak around the piston shaft, you should immediately determine if the piston shaft is an original PUR 40E shaft with a dark ceramic coating. This could be the case if the watermaker is an early PUR unit manufactured by Recovery Engineering or P&G. Katadyn units all use the improved piston shaft and shouldn't have this problem. In case you have an older PUR unit, determine which shaft you are dealing with by examining the pictures in "Known Problems With PUR Watermakers: Defective Piston Shaft" in my PUR/Katadyn Information article.

If you find that you have an original shaft (with the ceramic coating) installed, you will probably find that some of the ceramic coating has cracked or chipped off. This is what has damaged the seals and caused the leak. Obviously, it will do no good to replace the shaft seals without also replacing the shaft itself—the seals will just get torn up again in a very short time. You will need to contact the factory (or Katadyn North America) and obtain a replacement shaft. At the time of this writing, Katadyn was still offering improved shafts free of charge to owners of original PUR units. When ordering a new shaft, be sure to ask for a pair of new piston shaft seals, which should be replaced at the same time. Also ask for one of the small o-rings that is hidden between the piston shaft and the white plastic piston head; it is usually damaged during the shaft replacement procedure and should be replaced. Be aware that the threads of the new shaft should be coated with (green) Locktite® before the hex nut is installed. You can learn about this process in the Repairs Video on this CD. At the same time, use a magnifying glass to take a good look at the seal in the wiper block. If it's seriously damaged or worn, you should replace it too. Although it does not act as a seawater seal, it performs the important function of blocking (wiping) possible contaminants entering from outside the pump.

If you have one of the original defective piston shafts, and dealing directly with Katadyn is not a practical option, it has been suggested that a local machinist could carefully turn down the old shaft on a lathe to remove the ceramic coating and then polish the stainless surface. Although this might work (I don't know anyone who has tried it yet), my own guess is that the result would be a shaft with a slightly smaller diameter than the specs call for. That might cause the shaft seals to not seal adequately. If you know anyone who has tried this technique, I'd be interested in hearing the results. Send me an email (

The only other place I've seen a leak develop is at the junction of the pump body with the check valve plate or the pump back body. A leak at one (or both) of those locations might indicate a need to tighten the bolts holding the pump body parts together. However, it could also be caused by a defective or damaged o-ring seal. These are the large o-rings that create the seals at each end of the pump body cylinder. Since these o-rings are required to seal against significant internal pressure, it is important to detect and repair any leaks as early as possible. If there is enough clearance for water to weep out of the seal, it is quite likely that the o-ring will be extruded in the near future, causing a complete failure of the seal. Because of the pressure involved, I've actually seen those seals be squeezed out of their seats like peeling an onion. If the leak is slight and is detected early, try tightening the pump body bolts a little more to see if the leak stops, but be careful to not overtighten. If that fails, disassemble the pump and replace the large pump body o-rings. There are replacements in the Repair Seal Kit.

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