Water Filtering Systems

By Carolyn Shearlock, copyright 2011 . All rights reserved.

Easier for you and better for the environment

The first several charters we did, and trips aboard friends’ boat, I’ll admit that the topic of water filtration never crossed my mind.  Now, after six years of full-time cruising, I think it’s something every boater should seriously consider.  Actually, maybe a better way to state that is that I think it’s necessary and I hope you’ll consider adding one.

Why Filter?

No matter what type of “cruising” you do, even just afternoon day sails, you’ll benefit from a water filter:

  • Good-tasting water.  Even “pure” water will pick up a taste from the tank.  Plastic tanks seem to have more problems than stainless ones, but it can be a problem in any tank.
  • Remove chlorine.  Many cruisers use chlorine (straight bleach, not scented, 1/4 cup per 100 gallons) to keep “crud” from growing in their water tank and also to purify the water.  Freshly chlorinated water tastes bad and can cause problems in cooking — it will kill yeast in bread-making and yogurt cultures, for example.
  • Remove bacteria and “crud.”  If you don’t chlorinate the water in your tanks, all sorts of “crud” will grow in it, particularly if you’re in a warm climate.
  • Purify caught water.  If you catch rainwater, it can collect all sorts of stuff as it makes its way through the atmosphere and across your deck or tarp and into your tank.  Not just minute particles, but even leaves and other stuff.
  • Catch bugs that get into the tank.  We discovered that bugs would sometimes get in the tank through the vent.  You can’t close the vent, and even though we screened it off, some no-see-ums did make their way in.  A filter will catch these before they show up in your iced tea.

With a water filter, you’ll actually drink the water from your tank.  You won’t have to buy cases of little water bottles, resulting in less to carry, less to stow and less trash.  And all your cooking will taste that much better — not to mention being healthier!

Three Filtering Options

There are three broad classes of filtering:  after the tap or right at the tap (such as many of the Brita filters), a Seagull-type filter and a standard plumbing filter and housing.  Before deciding between these, however, you need to think about the purpose of the filter.  Simply stated, a filtering system that will work for occasional daysails or afternoons on the boat is not the same as what you’ll want if you’re heading to the tropics and plan to catch — and consume — rainwater.

Below, I’ll detail the pros and cons of each.

Image of a Brita pitcher1.  Filtering after/at the tap. Brita is probably the best-known maker of these systems.  They fall into three general types:pitchers, where the water is filtered going into the pitcher; bottles, where the water is filtered as you drink from the bottle; and tap filters that screw onto an existing faucet.

These systems are best for:

  • occasional use
  • removing unpleasant taste or chlorine (it’s a charcoal filter)
  • those needing a quick and very simple “installation” — no need to cut into water hoses
  • available at virtually every grocery store, drug store, discount store and more in the US

But:

  • relatively short filter life (most are 20 to 40 gallons) can make them expensive in the long run (about $6 for a 40-gallon filter makes it about 15 cents a gallon).
  • have to remember to fill the pitcher if you opt for the pitcher instead of the tap model (not always available)
  • no protection against giardia, molds or other microorganisms in the water
  • pitchers are inconvenient on a boat and very prone to spilling in the refrigerator (have to transfer water to a traditional bottle)
  • filter units can be hard to find in remote places and virtually impossible outside the US

Picture of Seagull system2.  Seagull Marine Water Filters. Seagull filters are truly the gold standard of filtering . . . and require a lot of gold both to buy initially and for the filters!

General Ecology, the company that makes the Seagull, states that “All Seagull IV purification systems are independently certified to meet EPA guide standard protocol for microbiological purifiers against bacteria, cysts and viruses. Plus, Seagull IV systems excel at removing chemical and aesthetic contaminants including herbicides, pesticides, chlorine and foul tastes, odors and colors.”  The Seagull comes with a dedicated faucet.

In researching this article, I found a very similar filter system called The Purest One (note:  the company has just changed hands and you send them an email by clicking on the “contact” button on the website — there is no other way to order online right now) which costs about one-third less than the Seagull and their filters are said to be interchangeable.  I don’t have first-hand experience with these, but the company says they exceed the Seagull standards.  If I were going to buy a Seagull-type filter system today, I’d buy The Purest One instead.

Best for:

  • Top of the line purification. If you know you’re going to be taking on truly suspicious water, it will do a great job.
  • Size constraints. It’s about 5″ in diameter and 5″ long, smaller than a standard housing.
  • Full-time cruising. Good, tasty water is always available at the tap.

The previous owner of Que Tal had installed a Seagull and we thought it produced great-tasting water.

But beware:

  • The Seagull is expensive — over $500 initially (comes with one filter and the dedicated faucet) and nearly $100 for a filter good for 1000 gallons (we found it lasted us about a year). That’s about 10 cents a gallon, which is less than the Brita and it offers much better filtering.  The Purest One retails for about $345 with the filters running $60.
  • Limited availability of filters. Unless youlive in acity with a large specialty store, you’ll have to buy filters online.  Forget buying them outside the US (I’ve been told they are NOT available in Canada, but that may have changed by now).
  • Some installation. This type of filter gets plumbed into the cold water hose and the housing has to be fairly near the faucet.  They claim it’s a twenty-minute job, but if you’re working in the typical confines of the under-sink galley cabinet and contorting yourself in the 3-square feet of galley floor space, it’ll take longer.  Changing filters can also be “interesting.”

Unlike the Brita filters and standard plumbing filters, the Seagull-type systems are sold in relatively few places.  While they may be available in some chandleries in very large boating cities, they generally have to be ordered online:

Image of Clear Water Filter Housing3.  “Standard” plumbing filters. There are all sorts of filter housings and connectors sold in hardware and home improvement stores.  While our boat, Que Tal, came with a Seagull system, this is what I’d install if I were starting with nothing.

Advantages:

  • Variable filtering level. You get to choose what type of filter you use in the housing from just improving the taste to removing various substances.  There are important differences in the filters — see my article on choosing the right filter for your application.
  • Easily obtainable. Go to any hardware or home improvement store and you’ll be able to walk out with what you need — even in most foreign countries (although perhaps not in tiny towns outside the US).  We never had problems finding 10″ filters in Mexico and Central America, although sometimes we couldn’t get exactly our preferred filtering level (we used them in our watermaker and also as a prefilter for the deck fill at marinas).  Reports from friends cruising in other areas say they’ve not had a problem.
  • Flexible installation. The filter housing can go anywhere, as in this photo graciously provided by Dawn of S/V Deep Playa.  You get to decide if you want a dedicated faucet, want it on the hot or cold water, on a foot pump or pressure water — or any combination.  And since you can buy all the parts in a local store, you can go, look, and figure out what’s best for your installation (some projects, such as this, Dave really likes to do hands-on planning).  And better yet, you can place it where it’s convenient (OK, there are few truly convenient places on the boat — but some flexibility helps!).
  • Inexpensive. The housings are $20 to $30, and you’ll need a few connectors, short bits of hose and hose clamps.  Filters vary in cost depending on the filtration level, but most are under $10 with a top-of-the-line filter available for $20 online and have a life of 10,000 to 12,000 gallons (although you’ll want to change them at least once a year).  Unless you have a very unusual installation, you should be able to get everything you initially need for $75, definitely for $100.

The only disadvantage that I know of is that you can’t get quite as good filtering as with the Seagull-type (I’ve never seen that “complete” a filter in a 10″ filter).  But you can get very good filtering.

If you decide to go with a standard plumbing filter:

  • Get one that uses standard 10″ filters.  They are by far the easiest to find and you’ll have the most choices of filtering levels.
  • I like a clear housing as you can see the state of the filter.  However, they can be a little harder to find and a little more expensive.
  • A filter wrench is nice, but not strictly necessary.  You can wrap a belt around the housing.  (NOTE:  depending on the installation, it can be impossible to use a filter wrench and you might be forced to just use a belt or a strap wrench).
  • Many housings now come with a shut-off valve in the top part.  These tend to cost a little more.  The valve is “nice” when changing filters, but not nearly as necessary as with a house system, since it’s easy to shut off your water pump.  Without the valve, you’ll probably spill some water in the locker, but it’s very likely that you’ll spill some out of the lower compartment anyway.  Our solution was just to put a rag below the housing before changing the filter and have a bowl or bucket nearby to dump it into.
  • Some housings have special quick connect fittings.  Reports from friends say these are more prone to leaks and require proprietary fittings that can be hard, if not impossible, to find after the initial installation.  If you use standard plumbing fittings, repairs requiring a replacement part will be much easier.

Whatever system you go with, enjoy drinking good-tasting water, coffee, tea, lemonade — as well as food that doesn’t taste like bad tank water!

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Comments

  1. Great timing as we are exploring our options for a “whole boat” filter to improve taste and insure healthy drinking water aboard Journey. Here I find you’ve done the research for me and now I can make the right choice. Thanks Carolyn!

    • Carolyn Shearlock says:

      We seriously underestimated how much we’d appreciate a water filter. QT came with one, but we hadn’t even considered it. Loved it, though — water always tasted great and we never had tummy troubles due to our onboard water. Hope you love yours just as much!

      -C

  2. Charlotte says:

    any experience with these filters?

    afwfilters.com/store/ro—drinking-reverse-osmosis/6-stage-di-zoi-delta-pure-reverse-osmosis-system-11.html

    They came with our boat and seem to work well
    Thanks!

    • Carolyn Shearlock says:

      Hi Charlotte!

      I don’t have any experience with them. Looks like a major purifying system. The only downside that I see is the size, but it looks like it removes pretty much everything (although not a watermaker designed to remove sea salt).

      -Carolyn

  3. Jed Guertin says:

    Carolyn,

    I’m quite familiar with the Seagull system and filter and PurestOne system and filter. I won’t go into detail but I might be able to provide you with some useful information for you to pass on to your readers.

    Simply put, if you put a good quality .5 micron (nominal) carbon block filter in your “plumber’s” filter housing in my estimation, you’ll have the same quality water as a Seagull filter.

    As far as I’ve been able to ascertain the General Ecology Seagull filter is not a purifier, never has been. It’s all about what I call weasel words.

    Fairwinds

    • I see that this article and the subsequent discussion threads are a couple years old. I’m hoping that the author is still active as I am struggling to find the right water filtration for two area of our boat. Currently we fill our tank in the US, primarily from a well water source. We live on board year round and the water is refreshed weekly. But I know there is crud in that tank and I get queasy thinking about bugs and other goobers. So I drink bottled water, but do cook with it without any problems. I do not use it for any appliances like coffee or tea. We also shower on board. So, here are my issue I hope to resolve with filtering.

      1. At the galley tap…want the purest water possible with everything out. Cold water only and not for dishwater. If I installed a separate faucet…I’d probably have it under the counter. Not sure I have an option for countertop with Corean. And I don’t want to give up counter space.

      2. It’s a hair thing. Tank water is killing my hair. We never put choline in. Tried it once and I hated it. Need so,e type of filter at the shower head for hot and cold water, or at least when they are mixed. Figure this will mount in the shower someplace, but not a lot of room. Also want everything filter out.

      3. Next year we begin cruising full time so we will install a water maker. Still will want the galley water we consume to be filtered. Although I’ve been told that made water is pure enough, I’m thinking its the tank that puts stuff back in that I don’t want. Expect this may be true of the shower as well, but I don’t know.

      Truth is, I don’t know what to do. I’ve been assigned this job on our boat and the more I read the more confused I get. I’m hoping this site is active or that someone who know and is interested,in helping me figure it out will contact me or respond here.

      Thank you thank you thank you in advance.
      Cheri

      • I’m not sure why you think the site isn’t active, as I write four new articles every week . . . and there is lots of activity on the Facebook page!

        Here’s what I’d do:

        Put a 10″ filter housing on each line exiting your water tank (clarification after a question: put it after the pump; some boats have more than one line & pump) and use a .5 micron carbon block filter in each one (read about the different types of filters here: http://theboatgalley.com/choosing-water-filter/ ) — this will give you the purest water possible and will also filter out any chlorine out. You can put these anywhere on the lines, wherever you have space as long as you can get to it to change the filter. If you also put a filter on the water line between the tank and the water heater, your hot water will be filtered, too (and you won’t have gunk settling in the water heater, either). This is the least expensive way to get good filtering that I know of (Sea Gull is good but very expensive and you need a separate faucet). This is option #3 on the article that you left your comment on: http://theboatgalley.com/water-filters/

        Next, flush your tanks with a lot of water — it’s the best way to get whatever is is there out. Then start filtering the dock water that you put into the tank, also with a .5 micron carbon block filter. The housing will fit on the end of the hose, then you can put a short stubby piece of hose after the filter to go to the deck fill. This will ensure that the water going into the tank is clean, although it will slow down the fill.
        Once all your water is filtered between the tank and the tap, you may want to start using chlorine again to make sure nothing grows in the tank (but only if the tank is stainless). We had a watermaker and still used chlorine. Just FYI, any type of carbon filter will take the chlorine out, so you don’t have to taste it or have it on your hair. If you were noticing the chlorine that much, I suspect that you were using too much.

        • Good site, thanks for the information! I’m looking to equip a new (to us) boat and it needs a water filter. On a previous boat we had a Seagull for drinking water and we were pleased with it, but on this boat I would like a whole-boat filter so we can brush our teeth in the head without worrying about water quality. I also don’t want to cut any new holes in the countertop for a separate faucet.

          In your experience, can a 0.5 micron 10″ x 2.5″ filter be used for the whole boat, or only for the small drinking water faucets? The specs on some of the filter manufacturer’s sites indicate low flow rates of around 1 gpm for these fine filters. That sounds a lot lower than the 3 gpm range that our pump will be pumping.

          You say “put a 10″ filter on each line exiting your water tank.” Do you mean on the inlet side of the water pump? I would think the filter would need to be on the outlet side of the pump.

          We are going to be catching rainwater. Do you think there is any advantage in using a series of 10″ filters–like a 10 micron pre-filter then a 0.5 micron fine filter, or is that just too complicated or too much flow reduction?

          Thanks for sharing your experience.

          • Exactly how you do it depends a lot on the boat configuration, how long the hose runs are and how powerful your water pump(s) is (there does NOT seem to a standard way of plumbing a boat!), but you’re right that the filter will probably be better on the outlet side of the pump (although we had a filter before the low pressure pump on our watermaker and it worked fine). If the filter is after the pump, the pressure switch will simply cut the pump off periodically if the pump is putting out water faster than it is flowing through the filter, and of course the water at the tap won’t flow any faster than it goes through the filter.

            Using a filter before the water heater (if you have one; we didn’t, just used a SunShower) will eliminate the gunk that collects in it and thus will lengthen the life of the water heater.

            We had a Seagull ourselves, but I do know of at least three boats that did use a single 10″ filter for both the galley and head (one head, and no freshwater flushing). And as you alluded, the biggest problem with using just one filter for the whole boat is the flow rate — although this does help with water conservation! That’s one reason that I like have separate filters on the hot and cold lines.

            Finally, on the rainwater catching . . . since that is just a gravity flow, I’d worry about not having enough pressure to push water through a fine filter and just backing up instead (in El Salvador, we would catch 20 to 50 gallons in 20 minutes or less at times). The head pressure is going to be so different on different boats and different catchment systems that I hate to make any blanket recommendations. With the premise that any filter is better than none, I’d probably go ahead and install the 10″ housing, then experiment with what filter is the finest that doesn’t restrict the flow too much (20 micron? 10 micron? you don’t need carbon as you’re not trying to get chlorine out at this point — more trying to catch sediment). While I know of several boats that talked about putting a filter on their rainwater catch, I don’t know of any that actually did (or if they did, I didn’t hear from them after they had installed it). If anyone else here has installed one, it would be great to know what worked for you — please leave a note in the replies.

          • Thanks for the reply. I wasn’t thinking of filtering the rainwater before it hit the tanks, only after it hits the boat’s freshwater system.

            I think the inlet filters you had on your watermaker were fairly coarse. We had a boat with a watermaker that used 20 micron filters on the inlet and 5 micron filters on the fresh water flush (which was between fresh water pump outlet and the watermaker inlet).

            Maybe the thing to do would be to put something like a 20 micron filter on the intake side of the fresh water pump to screen out any sediment from the tanks, and a 0.5 micron on the outlet side.

            But it sounds from what you said like the water flow will drop so low through the 0.5 micron filter that there wouldn’t be enough flow to run the shower. Maybe a better way is to just filter cold water to the galley faucet. That wouldn’t require another hole in the counter top, but it would mean brushing our teeth in the galley instead of the head. Oh well.

            Any comments from someone who has used a whole boat filter and who also uses their shower would be appreciated.

          • Hi Jim!

            I guess I should make clear that I don’t KNOW that the pressure drop will be too low for an acceptable shower if you use a 0.5 micron on its line; it’s just what I would be concerned about. I’m going to post a note on The Boat Galley’s Facebook page and see if anyone has tried using a 0.5 micron filter as a whole boat or shower filter and what their result was. Hopefully we’ll get some answers!

            If you want filtered water in the head sink, you could put a filter on that line in addition to the one in the galley. I don’t know your boat’s configuration, but our boat had a bunch of otherwise hard-to-access space under the head sink that could easily have been a home for a 10″ filter.

  4. Will the “standard” plumbing filter work with a simple hand pump or does it require the pressure created by a powered pump to operate efficiently?

  5. I know of several boats that used them with a hand or foot pump with no problem — and one that used a Seagull filter with a foot pump. We had a foot pump as a backup in our powered system and I had no problem using our Seagull with the foot pump, either.

  6. Dave Skolnick on Facebook says:

    I have a whole-boat filter. The element has both a mechanical filter and a carbon filter. It works great. Elements are a standard size but I haven’t found the combination units in the US, only in Europe.

  7. I have used these filters in combination with 10 or 20 micron paper filters ahead of the carbonated filter to supply the hotel water demands. They work fine. I would however caution against use of carbon filters when filling the water tanks as it will also remove the bromine which helps keep the water stored in tanks from going sour quickly.

  8. Chris van der Baars says:

    Just installed a Home Depot, GE 5 micron filter as a “whole system filter” on the intake side of the water pump on our Com Pac 25. It stopped the water flow to a trickle. I know it’s the filter because when I remove the element the water flow returns to the pre-filter rate. I installed an accumulator tank hoping that at least some of the water would make it into the 1 litre tank. No real improvement. I hate to give up …… any thoughts?
    Thanks…
    Chris.

    • Most filters are installed on the outlet side of the pump so that the pump can push water through it rather than have to pull water through it. I’d try moving it to the outlet side.

      • Belated thanks for your suggestion of moving the filter to the outlet side of the pump.
        We have been on the boat continuously since mid-June and can share our findings about our “Home Depot” systems.
        As mentioned previously, I moved the filter to the outlet side of the pump and then installed a 1 litre accumulator tank after the filter. The result is, no surprise, good flow from the accumulator tank but an immediate reduction of flow when the tank is emptied. The pump cannot push the water through the filter to provide a continuopus flow.
        All in all, an adequate system for us marina based people who have showers available shore-side and enjoy fresh water sailing.
        The water quality is excellent.

  9. We use a PUR faucet mount that lasts 100 gallons , removes Giardia and Cryptospiridium, reduces chlorine and tastes good. Available on Amazon and any home improvement store.

  10. Sally Conlee says:

    The Purest One website does not appear to be working. The phone numbers are disconnected.

    • Thanks for letting me know. I did some investigating and found that the company has recently changed hands and they are trying to re-do the website. Right now, you can contact them by email — click on the contact button on the website (I changed the link so that it goes to the “new” site).

  11. Colin MacDonald says:

    Thank you for information on PurestOne filter/Seagull, I am thinking of installing one my boat inline on out let of my main water pump after the accumulator thank and exciting water faucet. any thoughts on this plan I will have to order from Canada on line and get ship to Canada

  12. Ken Arnold says:

    The 10″ House filters also have a “Ceramic Bacteria” filter avail. for about $30-40. It can be cleaned w/ a steel wool (stainless) scrubber pad. It is very slow flow and really needs a Pleated or Carbon Block filter “prefilter” or it will plug fast.

    You just scrub the sides of it lightly to make it like new.

  13. We added a refrigerator type filter and a spigot on the counter above the refrigerator in our Tayana ’42. The line and the filter were in the refrigerator and we had cold tap water. We had installed a DC refrigerator system in the original frig.

  14. Just writing about our water today. We have particle for all water and ceramic for drinking water.

  15. Just sanitized & filled my tanks yesterday, as well as replacing the pressure pump. Thanks for this summary…I was thinking about putting in some type of filter!

  16. Nancy, I know another boat that did that. Great way to get cold water if the layout works!

  17. We have a filter tap on our Liberty 458 ! It’s brilliant

  18. I always do! Okey, almost…

  19. I bought a filter system from the purest one based on your recommendation and we love it!

  20. We run the standard 10″ filter on our foot pump but I have found that the more aggressive filters esp charcoal ones are too restrictive and the foot pump has a hard time moving the water. I’ve tried putting the filter on either side of the whale foot pump to no avail. We are a family of 4 living full time aboard and we just use basic 5 micron filters and drink rain water. Our catcher dumps right into our tank. Tastes great

  21. Great post. Our boat also came equipped with a Seagull filter. I’ll definitely check into the Purest One replacement filters for next time!

  22. 4 Tlbs. Of Clorox to my 40 gal. Tank kill bacteria,germs and bad taste.

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