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How To Maintain A Freshwater Tank

Here's how to restore your water tank or tanks to like-new condition, with minimal effort.

Water Tank Hygiene 101

There’s no way of getting around it—potable water on board cools its heels for much of the time. So, given bacteria’s exuberant nature, there’s no question that that potable-water tank of yours, down in the engine room, needs to be addressed in some shape or form at this time of year, whether it happens to be made of plastic or some sort of metal.

For starters, drain off most of the water in the tank, pop the inspection port—most potable tanks have them—and run your finger around inside. If there’s slime and/or a bad smell, figure on draining the remaining water and thoroughly cleaning the interior of the tank. From the standpoint of hygiene, this is necessary even if you only drink bottled water on board.

Cleaning can be handled in a couple of ways. The first entails swabbing as much of the inside of the tank as possible with a soapy sponge, flushing the grubby contents, and then, after refilling the tank with clean water and a small amount of dishwashing detergent—overdoing it can extend the rinse cycle into eternity—agitating the mixture with a long-handled brush, a propeller-type paint stirring device secured in the chuck of a powerful cordless drill, or some other mechanical means.

The second method’s more fun. It entails swabbing and flushing as before but then refilling the tank only about halfway and going for a little boat ride in conditions sporty enough to thoroughly clean the inside of the tank, washing-machine style. The longer the boat ride—the cleaner the tank!

In any case, after you’ve returned your water tank or tanks to like-new condition, you may want to add a “Whole House” filter system from Home Depot or Lowe’s downstream of the pump that pressurizes the entire freshwater system. If you decide to do this, one of the best options pairs an activated-charcoal-based unit with another that removes particulate matter. A slightly less complex option simply adds a filter to the faucet you designate for drinking and dishwashing alone.

Just remember. Most experts advise taking a pass on drinking any kind of water (filtered or not) after it’s languished in a boat’s tanks for weeks on end. Of course, using a fresh-water system every day, during a liveaboard stint that constantly renews what’s in the tanks, engenders quite another story, especially if filters are involved.


For more tips like this, visit the Vetus-Maxwell DIY Workshop at

Capt. Bill Pike is deputy editor of our sister publication Power & Motoryacht magazine.