Do-It-Yourself Water Filtration

Do-It-Yourself Water Filtration

One of the first things that you realize after a few seasons of cruising is that approaches to life aboard vary between two wide extremes: cruisers who by choice or because of a limited budget live with minimal creature comforts, and those cruisers who sacrifice little more than living space when they move aboard.

You’d think that when it came to basic essentials like food and water, there would be some overlap between these two groups, but that isn’t necessarily the case. Take water, for example.

During his circumnavigation, Practical Sailor editor-at-large Nick Nicholson (no relation) installed a General Ecology Seagull IV filter, an expensive solution, but one he felt was worth it. My wife and I, meanwhile, used local water where we roamed, which included some remote areas of South America, the Pacific, and Southeast Asia, with little or no treatment during most of our 10 years of living aboard.

In the few areas where water seemed sketchy, we followed Lin and Larry Pardey’s general guidelines in their book The Care and Feeding of the Offshore Crew for chlorine treatment. We would treat the water in jerry jugs before pouring it into our tanks. As I recall, that practice only lasted about a year, when we noticed that many of the locals seemed a lot healthier than the folks back home, and our concerns about drinking the local water was replaced by tropical languor.

Nick reported that most cruising boats he met during his first year of tropical cruising had some type of watermaker, but usually chose to take advantage of the local water supply when dockside or anchored in polluted harbors. When we were cruising abroad in the early 90s, it seemed that less than half the boats we met regularly used watermakers.

The Nitty Gritty

All shore-sourced water supplies, either in the U.S. or overseas, contain particulate matter. This may be pipe scale, sand, small bits of grass, or other types of sediment. While not necessarily harmful, sediment builds up in your boats plumbing. It can settle in the bottom of tanks, only to get stirred up during an offshore passage. Over time, it can wreak havoc with water pumps, destroy ceramic water fixture cartridges, and prevent the seating of rubber faucet washers.

Nick learned this the hard way when his Grohe faucets started leaking after two years. Fortunately, replacing the cartridges was easy-once he found them-but after that experience, he became determined to reduce sediment in the entire water system.

My wife and I had no problems with sediment fouling our pumps, probably because we relied solely on forgiving diaphragm foot pumps from Whale. We went through three foot-pumps in 10 years, but that was because plastic housings cracked through hard use, not because of sediment. We did flush out our tanks pretty regularly when the water was looking more soupy than usual. I don’t necessarily condone our approach. I felt we were careful enough, and it was simply what we did-another data point to consider, so to speak. I suspect Nick might have the last laugh when doctors discover some sort of parasite consuming my innards, but so far my wife and I are doing just fine in spite of our relatively lackadaisical approach to water (knock on wood).

Protecting Your Water Pumps

If you do have a more sensitive impellor-type pump on your boat, protection is relatively simple. Just install an in-line sediment strainer just upstream from your freshwater pressure pump. Nick used a Par Pumpgard filter, positioned to be easily accessible for routine checking and cleaning. This is a compact, small-capacity stainless-steel mesh strainer in a clear plastic housing. Most of the toilets in our recent toilet test came with these filters, as safeguards against pump damage. They are relatively cheap-about $20 at any marine store.

A Simple Pre-Filter

In Grenada, Nick ran into a couple on a well-equipped Baba 35 who pre-filtered shore water before it even got to the boat, and he later adopted that approach. On a trip back to the States, he picked up a $20 Omni filter housing at a home supply store. GE makes a similar one, as well. The one Nick bought uses standard 9.5-inch filter elements, which he found available worldwide. For a few dollars more, you can get a clear filter housing that allows you to monitor the state of the filter element more easily.

The rest of his custom pre-filter system comprised two plastic hose nipples screwed into the filter housing, a pair of hose clamps, 4 feet of .75-inch reinforced PVC water hose, and a couple of plastic garden hose end fittings. To use the simple in-line filter, Nick would screw the filter inlet hose to the shoreside water bib, then couple the boats water hose to the filters outlet.

Total cost of this handy gadget today is about $45, including a couple of spare 30-micron sediment filter cartridges. Flow rate through the filter is about four gallons per minute, so it provides minimal increase in your watering time.

Another option is the funnel-type water filter that Tech Editor Drew Frye made using ordinary PVC. The filter requires a slower fill rate, but also works with rain water, which can be contaminated by dirt or soil on the rain catcher.

Serious Filtration

All the drinking water aboard Nicks Calypso, even the water they made themselves, went through a General Ecology Seagull IV purification system. This expensive filtering system-list price is over $700-will remove just about everything harmful from water, according to the manufacturer. Any water considered bacteriologically acceptable for treatment by the U.S. Public Health Service standards can be rendered safe by the Seagull IV.

The components of the Seagull IV model X-IF-the most common version seen aboard boats-are a compact stainless-steel filter housing with bulkhead mounting bracket, a nice sink-mounted faucet, plus the appropriate hookup hardware. You also get one filter element, which is good for about a year. Spare filter elements are not cheap at about $90 each. Nick mounted the filter housing under the galley sink and plumbed the filter straight into the pressurized side of our freshwater system through a T-fitting. An in-line shutoff valve upstream of the filter makes it possible to change filter elements without shutting down and draining the water system.

Even today, when I can better afford Nicks approach, it seems a little expensive. I wouldnt call it overkill, especially now that I have a greater appreciation of the importance of good health, but I suspect there are some more affordable options out there that are just as effective.

If you have some inexpensive water treatment systems to share, please include them in the comments below. In the meantime, were rounding up some new products from General Ecology (makers of the popular Seagull IV treatment device) and other makers to see if we can hunt down any bargains. The growing popularity of portable ultraviolet systems seems to offer some new avenues that well be exploring as well.

Its my feeling that there are probably a number of home-purifying systems that would be readily adaptable to a boat at less expense. If you know of a sensible water treatment product for us to look at, let us know below in the comments section or by emailing me at [email protected].

Darrell Nicholson
Practical Sailor has been independently testing and reporting on sailboats and sailing gear for more than 50 years. Its independent tests are carried out by experienced sailors and marine industry professionals dedicated to providing objective evaluation and reporting about boats, gear, and the skills required to cross oceans. Practical Sailor is edited by Darrell Nicholson, a long-time liveaboard sailor and trans-Pacific cruiser who has been director of Belvoir Media Group's marine division since 2005. He holds a U.S. Coast Guard 100-ton Master license, has logged tens of thousands of miles in three oceans, and has skippered everything from pilot boats to day charter cats. His weekly blog Inside Practical Sailor offers an inside look at current research and gear tests at Practical Sailor, while his award-winning column,"Rhumb Lines," tracks boating trends and reflects upon the sailing life. He sails a Sparkman & Stephens-designed Yankee 30 out of St. Petersburg, Florida. You can reach him at