Maintaining Clean Water Aboard Your Trawler

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Senior Member
Oct 6, 2007
Clean water aboard our boats is something we take for granted. While living aboard a boat, especially when you are cruising, is that your water supply is usually limited while away from the docks.

My wife and I use 12 gallons a day, or enough for 25 days without refilling aboard our trawler, the Patricia Ann.* Our usage includes bathing, and cooking meals.* That's with a 300 gallon water tank.* And of course, conservation is critical; no standing in the shower for 15 minutes.* You can determine your daily use on your boat by timing the filling of a 5-gallon bucket, then timing the filling of you water tank.* Simply divide the time it takes to fill your storage tanks by the time it took to fill your 5 gallon bucket, and then multiply by 5 gallons and you have the amount of water you have used since last filling.

Tank fill time / Bucket fill time x 5 gallons = Total water use

Shore Based Water

Water quality is as important as quantity. While you are cruising in uknown areas, the water quality can vary.* In most cases you will not know if the water you wil be using is city or well water.* If it is not city water, you do not know if it has been treated.* Several months ago, our marina had a well problem at the well head causing the water supply to become contaminated with e coli bacteria. It took over a week to get it cleared up. I am certain some of the local marina customers must have used that water too.

But on the Patricia Ann, we had safe drinking water; how you ask? We have a 5 stage filtration system that provides bottle-like clean water from any suspect source. Water goes through 2, 5-micron filters, then a single 2-micron filter,* and a carbon filter to remove cysts and undesirable tastes.* Then finally a UV radiation light to kill any bacteria before it enters the holding tank. The power source is 110 volt ac but it can be ordered with a 12 volt system.* The resulting water tastes a pure as bottled water.

You just bought that used trawler; what can you do about the existing water in her tanks?* Standard Chlorox will treat that water acceptable for drinking.

Use 1 teaspoon of bleach for every 10 gallons of water; if the water is cloudy, double the dosage.

Rainwater Runoff

I have also seen setups on trawlers, where rainwater runoff is collected from upper decks and funneled into the holding storage tanks.* This is pretty good source of water but there is still concern about the quality of the rain water that would affect the taste of the water and perhaps cause tank corrosion.* Be sure you have a good idea of the air quality in the area.* If the area you are in is highly industrialized, acid rain could be an issue

Water Makers

Now of course, you can set up a watermaker aboard your trawler and have virtually unlimited water.* All water makers designed for small boats and yachts rely on essentially the same technology, exploiting the principle of "reverse osmosis"; a high pressure pump forces sal****er through a membrane which allows water but not salt to pass.* The price of water makers bought* are established by the amount of water they produce on a daily basis.* If your cruising will take you to the islands, keep in mind that water if purchased, can cost more that fuel* Watermakers are a virtual requirement.
One caution is clear tanks or any FW hookup with clear tubing in the system.

Light helps the green stuff grow , no light less growth.

Our preference is Flaired 5/8 refrigeration grade copper tubing.

EZ to install, and no heat required to replace a damaged section.

Copper takes longer to install than Pex , and is less freeze resistant but seems better with the tank bugs.
On our prior boat, a catamaran, we had 2 aluminum tank that had "crystals" inside as a result of chlorine in city water. *I thoroughly cleaned the tanks and purchased a household water filter with replaceable cartridges that eliminate, cysts, chlorine etc and hooked it up between the water source and another hose outlet to fill our tanks. *We always had good drinking water aboard after that and did extensive cruising on her. *Will do the same on our new (to us) trawler.
RO systems vary in price.
Here in Aus and I expect the same elsewhere you buy from established makers like Village Marine etc, expensive.
Or buy from a local manufaturer , low overheads and possibly no frills much cheaper.

I recently installed a 120 lt/hr (30 gal) unit with a S/S HP pump . No frills except for a cheap salinometer. $8000.00 Have had it for over a year and absolutely happy with the install which I did myself.
On installation I then cut down my s/s water tanks from 2 x 1000 lts to 2 x 500 lts and thus increasing my lazzerette storage (wine & beer).
The same unit 1/2 the capacity (1 membrane instead of 2) and a brass HP pump $5500.00

They increase your selfsufficiency like you wouldn't believe.

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