Tips On Installing The 40E Watermaker


In this article, we'll be looking at some tips to keep in mind when planning the installation of a model 40E watermaker. Those of you with already installed units might want to consider the benefits in making some changes to your original installation. You are also strongly encouraged to read the sections on installation in my Watermaker Book and in the Katadyn 40E Owner's Manual. You can use any of the links below to quickly jump to the major topics discussed in this article.


Planning the Installation:  Let's start out with some useful tips that you should consider during the planning stage. First you need to decide where the intake seawater will be coming from. You'll want to consider this at the same time you think about where the watermaker prefilter assembly and pump will be located. Try to minimize the length and number (and severity) of bends that will be required in the hose runs.

There are two basic choices:  first, you can tee into an existing intake system, such as the cooling water for your engine, head, refrigeration system, etc.  The second choice, of course, would be another separate thruhull dedicated to the watermaker.

Plan the seawater inlet location carefully. Locate it well below the waterline.

Although the latter choice is the best overall, it usually involves more work and expense, including punching another hole in the hull. Many cruisers are of the opinion that the fewer holes in the hull below the waterline, the better. I won't argue with that.

In either case, the intake thruhull must be mounted well below the waterline. In this context, it's important to remember that the waterline is not a fixed thing, especially on a sailboat. It's amazing how much of the hull is out of the water on the windward side of a sailboat under sail. Be aware that it takes a surprisingly modest amount of air intake to dramatically degrade the quality and quantity of your watermaker's product water output. I've encountered several cases of boats with this problem, even in a rolly anchorage situation. Plan ahead.


Consider Installing a Seawater Strainer: My next suggestion is to install a seawater strainer in the intake line. In my experience, a strainer is absolutely critical for the intake to your engine and also the seawater intake to your head. In the case of your engine, a small piece of hard flotsam, like a piece of wood, can rapidly destroy the impeller in your saltwater pump and take your engine down from overheating. Depending on your situation if and when it happens, that could be a serious problem.

TIP: Install a coarse seawater strainer at the intake.

With your head intake, be aware that, especially when you are at anchor, the little intake thruhull is a very appealing hiding place for various small sea creatures, like a young octopus or kelp fish. Once you suck one of them up, it will become lodged in the rim of the toilet bowl, unable to pass through the small flush water holes of your toilet, and it will stay there until it rots. I guarantee that, long before it has rotted into nothingness, the smell from your head will force you to do one of the only two things possible at that point, which is to remove the toilet bowl and backflush it with a pressurized water hose to remove the dead and decaying animal. That task is not one any cruiser looks forward to. (Your other option, of course, is to sell the boat at below fair market value). For the intake to your watermaker, a seastrainer is more of an optional item, but still useful for the same reasons. My intake system

Consider my own system as a typical example of the basic elements involved at the seawater intake site. (See the photo to the right). With my installation, I chose to tee off of the intake to the seawater pump on my diesel engine. First in line is the thruhull itself. Immediately following that is a seacock. Every hull opening to seawater should have a seacock installed immediately after the thruhull, and it should be in a location that is easily accessible. Next in line is the seawater strainer. In my case, the output side of the strainer feeds into a pipe tee. The tee feeds downward to the hose going to my engine's seawater pump. You can't see that well in this picture. The upward branch of the tee goes to the watermaker. Note that I've installed a second seacock in the watermaker intake line. This enables me to shut off the connection to the watermaker when, for some reason, I need to service it, without affecting water flow to the engine.

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Prefilter Location:  My third tip is, in my opinion, probably the most important of all, as far as getting long term satisfactory operation from your watermaker is concerned. It's the thing I stress most heavily in my seminars: locate your prefilter assembly in a place that is VERY EASY to access. To keep your watermaker producing good quality product water, you'll need to be getting at the prefilter often, perhaps daily. I'll have much more to say on this topic in my article on Use & Maintenance. I really can't emphasize this point strongly enough.

TIP: Locate the prefilter where it's easy to get at.

Again, I'll use my own experience as an example. I'll confess that when I first installed my original Model 35 back in 1995, I installed the watermaker and the prefilter assembly in a remote, unutilized location far back in a lazarette compartment. I was pleased to have found a use for some available empty space. However, I didn't stay pleased for long. I soon realized that, to get at the prefilter assembly, I had to pull everything out of the lazarette, physically crawl down into a confined space, and then invariably scratch my arms on the unfinished fiberglass surface of the hull—all in order to get at the prefilter. It was not a good choice for location.

My convenient prefilter location

When I finally decided I had to install my watermaker in a more accessible place, I still chose the same lazarette compartment because it was far enough away from the main cabin to minimize noise when the watermaker was running. But this time I made a much wiser choice of location. All I had to do was lift the lazarette cover and my prefilter was right there—easy to get at and service.

Take a closer look at the advantages of this type of installation. First, as I've already mentioned, notice how accessible the prefilter assembly is. All I have to do is reach down and unscrew the bowl to change the prefilter cartridge. I also installed extra long lengths of hose for the product water output. This allows me to route my product water out into the cockpit for easy quality testing. It is also easier to fill extra potable water containers, if needed.

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Avoiding Air Leaks:  There's one last but very important point I want to make about the prefilter installation. In my experience servicing PUR and Katadyn watermakers over many years, I've found that the number two most common problem is air getting sucked into the intake system somewhere. The number one problem, by the way, is the rotten egg smell dilemma. I'll discuss the cause and solution to that in the Use & Maintenance article.

By far, the most common source of air ingress to the watermaker is at the prefilter housing. It's amazing how little air is needed to cause the product water output to greatly diminish or cease altogether. The reason is because air, unlike water, is highly compressible. A small amount of air leaking into the intake plumbing works like a sponge and prevents the low-volume watermaker pump from developing the high pressure required to squeeze product water through the membrane. It's as simple as that.

How do you detect an air leak at the prefilter housing? Run the watermaker and use a flashlight held behind the intake and output hoses. If there are no air bubbles flowing into the prefilter housing, but you can see air bubbles flowing out through the output hose, then it's likely you have an air leak. Be aware, however, that bubbles flowing from the output of the prefilter could also be cavitation bubbles, not air. This could be the case if seawater flow is severely restricted. I discuss this situation in more depth in the article on Troubleshooting.

Likely sources of air leaks

There are three sources of air leaks at the prefilter housing: the intake fitting, the output fitting, and the housing o-ring seal. The plastic pipe-to-hose barb adapters supplied with a new watermaker are tricky to install correctly. The problem is not at the hose barb end; it's where the pipe thread screws into the top of the prefilter assembly. It's very easy to overtighten these adapters—in which case the fitting will pop back a thread—or not tighten them enough. In either case, there's likely to be an air leak. Years ago, one of the repair technicians at Recovery Engineering gave me a valuable tip: coat the pipe adapter threads with a non-hardening pipe joint sealant, like Permatex, when installing them. I've found that suggestion, along with a warning about overtightening, usually works well to prevent air leaks at these connections.

The seal at the bowl of the prefilter housing is maintained by the large o-ring inside. In you have problems here, first, always make sure the o-ring is actually there. I know of several cases where a cruiser dumping the old water out of the prefilter bowl overboard when changing out the filter element, also dumped the o-ring at the same time without noticing. It's all too easy to do. Be forewarned. Second, make sure the o-ring is well lubricated with silicon grease, seated well, and that the housing bowl is screwed on tight.

BTW, if you're a serious technophile, you might want to know what kind of "below ambient" pressure the prefilter housing is designed to withstand. I wondered the same thing a few years ago. What I discovered, after inquiring of the factory, is that there are not any specifications from Ametek (manufacturer of the filter housing) covering operation at pressures less than ambient. The prefilter housing was actually designed to withstand positive pressures higher than ambient (e.g., typical pressures from household pressurized water systems in the neighborhood of 40 psi). There are no manufacturer specifications for the type of use to which we watermaker owners are putting the assembly. Caveat emptor!

Even these precautions may not be enough if your intake water source is teed into a supply line to another competing piece of equipment, like the seawater intake for your engine or refrigeration system. In cases like that, the watermaker is drawing its intake water from a source that is already at less than ambient pressure (when the other equipment is running), which increases the possibility of an air leak. If that's the case, you might try obtaining an o-ring that is fatter than the original or, in the worst case, consider installing a dedicated intake thruhull for your watermaker.

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Watermaker Pump Location:  Where you decide to locate the pump itself isn't nearly as critical as the prefilter location, but there are a couple of things to consider. First, find a place where the small amount of noise the watermaker makes when running will be tolerable and, second, consider the strong possibility—in fact, the probability—that the watermaker could, at some future time, develop a leak. Locate it where any seawater dripping from it won't damage vulnerable supplies or equipment. Finally, I strongly advise against locating the pump and drive unit in an engine compartment. The electric motor on the drive unit has a maximum ambient temperature rating of about 40°C (104°F). I don't think I've ever seen an engine room that didn't get hotter than that, unless it was air-conditioned. Such high temperatures can shorten the life of the electric motor and, in some circumstances, contribute to drying out the membrane, which will ruin it.

Typical pump location

When planning how and where to mount the pump unit, the only restriction that is important is to make sure the membrane housing and pump body are on a horizontal line. The reason for this is twofold. If the membrane housing and pump were at a lower level than the drive and gearbox, there's a chance that oil could run down the drive shaft and find its way into the pump in the event that the drive unit developed a leak. This could rapidly cause fatal damage to the membrane. On the other hand, if the pump were higher than the drive unit, a seawater leak from the pump could travel toward the drive unit and cause problems there. In the latter case, the main problem is the possibility of corrosion affecting the drive unit. (See my discussion of that problem in the PUR/Katadyn Information article under the topic about defective piston shafts, and you can view a good example of that kind of damage in the disassembly section of the Repairs Video.)

As long as the pump/drive unit horizontal restriction is followed, the drive can be rotated to any position around that horizontal axis. In my case, I've installed the pump unit farther back in my lazarette compartment, but near enough to the prefilter to minimize the hose runs. I also installed a dedicated 1/2" thruhull behind the pump for discharging the reject water. Aside from needing access to the pump once or twice a year for servicing or maintenance, you really shouldn't need to get at it very often.

There's one last point to consider when planning the location for the watermaker pump. There is an old but persistent rumor you might hear about how the pump unit must be located below the waterline. This is completely false! The pump is a positive displacement pump and is self-priming. Its principle of operation is essentially the same as an old hand-crank water well pump. It can draw water upwards several feet with no problem at all. I've offered some speculations as to the source of that false rumor in my watermaker book.

In any event, I actually discourage owners from installing the watermaker below the waterline for several reasons. First, the motor and gearbox are not waterproof. Installing it below the waterline dramatically increases the chances that the drive unit could be damaged from exposure to bilge water. Second, available space below the waterline is typically very limited and often not easily accessible. Finally, installing anything below the waterline is usually a frustrating and masochistic chore. I can't do it without emerging at the end of the project with numerous bruises and fiberglas scratches on my arms!

Of course, you should always try to minimize the length of your hose runs, the number and sharpness of bends in the hoses, and the height of the pump and prefilter assembly above the waterline. Nevertheless, the fact is, you have quite a bit of latitude for all of these variables. When you think about it, the amount of intake seawater the watermaker requires in order to run well is rather small—approximately 15 gallons per hour. By way of comparison, the smallest bilge pump I've seen—the size we installed in our shower sump—moves about 400 gallons of water per hour! Bottom line: the watermaker pump really doesn't have to work too hard to obtain 15 gallons of intake seawater per hour. Most of its power is used to press product water through the membrane at 800 psi.

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The Electrical Connections:  Here are some tips on your electrical connections. Take the time to do it right. Install a terminal strip near the pump and use ring terminals on the wires coming from your power source and from the pump. Don't be tempted to use simple butt connectors. If you do, you'll have to cut them off and shorten the wires every time you need to dismount the watermaker for maintenance. The wires will become shorter and shorter and you'll need new butt connectors each time. Using a terminal block and ring terminals not only avoids these problems, but also provides a handy place for voltage testing in case you have to do some electrical troubleshooting.

Preferred type of Electrical Connections

Another valuable technique is to make your electrical connections with a service loop that bends downward as it exits the terminal block. This method accomplishes two things: you'll have enough extra wire length to re-terminate the connections, if ever needed. Also, if water happens to get splashed on the wiring, it will drip off the low end of the wire loops, instead of draining down onto the terminal block, where it can rapidly cause corrosion.

And here's a final tip on marine electrical wiring, for those of you who are really gung-ho. If you've been around boats for very long, you'll surely have noticed that, once a wire is exposed to seawater, it quickly starts to corrode. Over time, the corrosion migrates up the wire for several feet. It not only turns the copper wire black, but creates poor electrical connectivity and eventually destroys the wire altogether. On all my electrical connections on our boat, I first pull off the plastic insulator ferrule on the crimp terminal. Then I crimp the bare metal terminal to the wire and solder it. Next, I coat the terminal ferrule and exposed end of the wire with 3M Scotchcote. Finally, I apply a length of shrinkwrap, the kind with a melt liner inside. I've never had a wire go bad that was terminated that way. I learned that method while working as an electronics technician and submersible pilot for Oceaneering, Int., back in the early eighties. It works, and in my opinion, it's well worth the extra effort over the long term.

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Routing the Product Water:  O.K., while we're here, let's consider another point that is of particular importance to those of you who are bluewater cruisers. By that I mean sailors who make long distance voyages, far from land, support facilities, or sources of potable water. The installation directions I've seen that are provided by most watermaker vendors recommend that the product water output can—and should—be routed directly into your primary potable water storage tank(s)—after testing for quality, of course.  In my opinion, this is another one of those ideas that look good on paper but can cause serious problems in the real world of cruising.

TIP: Don't route your product water directly into your primary potable water storage tank.

Consider this:  suppose you were halfway across the Pacific Ocean on a long passage from Mexico to the Marquesas. Let's also assume that you depend on a single potable water storage tank and, following the recommendations of your watermaker vendor, you've plumbed the product water output from your watermaker directly into that single storage tank. Being the cautious type, you religiously test the quality of your product water at the beginning of each run, before redirecting it to your potable water storage tank. But now imagine that your watermaker fails—for whatever reason—at some time during the run and starts delivering raw seawater into your storage tank. It's a worst case scenario, I realize, but it could happen. In fact, I know of at least one instance where it did. Now you've got a serious problem.

Collect water in jerry jugs

That's why I strongly recommend that you figure out some way to be sure that you always have some minimum, but adequate, quantity of known good potable water available at all times. In our case, I solved this problem in two ways. First, I always collect my product water into two six-gallon jerry jugs, as you can see in the picture on the right. I test the quality of the product water at the beginning and at the end of each watermaker run. It's not that hard—all you really need to do is taste it. Only when I'm certain that the collected water is of good quality do I manually transfer the water from the jerry jugs into our single potable water holding tank. Secondly, I schedule my watermaking runs to make sure that I have at least twelve gallons of known good water at any time, either in the main storage tank or in the jerry jugs.

One of the great advantages of having a watermaker—as we discovered—is the possibility of being able to free up a large amount of valuable storage space by eliminating unnecessary potable water tankage. We originally had two 30-gallon water tanks, port and starboard. When we installed our watermaker, we converted one of the tanks to dry goods storage. This left us with only one tank for water storage. This works well, but only if you pay attention to the need for a reasonable amount of known-good potable water at all times. Again, this is of special concern mainly for those who do bluewater cruising. If your cruising style is limited to one- or two-day passages from one port or anchorage to the next, or if you have more than one potable water storage tank, and they are suitably isolated from each other, this caution isn't quite so important. But, think about it, and plan ahead for the kind of cruising you want to do. Serious bluewater cruising demands that you consider how you'll get by if any piece of equipment should fail!

By the way, you may have noticed that I have two product water hoses feeding my jerry jugs. The reason is because I actually have two watermakers running off of a single prefilter system. I have my original model 35 and also a model 40E, both of which I can run at the same time, or individually. This is just one example of my belief in redundant systems for critical equipment on our boat. I'll have more to say about that elsewhere. Also, some of you will probably notice that my prefilter housing is opaque white. That's because it's the original housing that shipped with the old model 35. When Recovery Engineering introduced the Endurance models—the 40E, 80E and 160E—they changed to a clear plastic housing.

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Consider Using a Larger Hose Size:  I have one final suggestion for your consideration. The Model 40E ships with enough reinforced plastic hose to accommodate just about any installation configuration. However, the hose is 7/16" ID. Although it's perfectly adequate for a single 40E installation, there are a couple of potential problems. First, if for some reason you were to need more hose, it's very difficult to find anything smaller than 1/2“ reinforced hose in most chandleries and marine supply stores. The same goes for thruhull and seacock sizes. Secondly, if you ever anticipate wanting to upgrade to one of the larger capacity Katadyn watermakers, they will require 1/2“ hose. Finally, if you decide to install two smaller watermakers in order to implement redundant capabilities —as we did—you'll want a larger hose size to run the two watermakers off of a single intake system. If you're doing a from-scratch watermaker installation of a 40E, seriously consider buying and using 1/2“ reinforced plastic hose from the outset. You'll also need to buy some new pipe-thread to 1/2“ hose barb adaptors for the prefilter housing and the intake and reject fittings on the pump.