Clean water on board our yachts is something we take for granted. One of the issues while living aboard, especially while cruising is that you do usually have a limited supply 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 find 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 Water

Water quality is as important as quantity. While cruising, you never know what quality your water will be. You will not know whether the water you will be using is city water 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 ecoli bacteria. It took a week to get it cleared up. Some of the marina locals must surely have used the water before the problem was discovered.

However on the Patricia Ann, we had ample safe drinking water. Our trawler is equipped with a 5 stage filtration system that will provide high quality water from almost any 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.

So what if you have just bought that used trawler and are concerned about the existing water in her tanks? Ordinary bleach will treat water suitable for drinking.

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

Rainwater

I have investigated other trawler setups where rain water runoff is collected and funneled into the water 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. My caution would be to be sure of the air quality in your area. If the area you are in is highly industrialized, acid rain could be an issue

Watermakers

Installing a watermaker in your boat will give you an almost unlimited water supply. 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 saltwater through a membrane which allows water but not salt to pass. Watermakers are priced by the amount of water they produce in a days time. If your cruising takes you to desolate islands in the Bahamas, keep in mind that water if purchased can cost as much as fuel. Watermakers are a virtual necessity.