How To Clean A Fresh Water System

Water Deck Fill

Looking around at discussion boards online, it seems that many boaters have a common springtime affliction: how to clean your water tank to bring your taps back to sparkling clean H20.

One common instruction is plainly to not drink the water on board, unless you live aboard full time.  Living aboard gives you the ability to constantly monitor the condition of the water coming in and going out, and the water will get used and refreshed a lot more often.

If you're anything less than a full time live-aboard, shower and hand-washing use is acceptable, but don't drink it or use it to brush your teeth.  Do so at your own risk, anyway!

How to flush the fresh water system in the spring:

1. Shock the system.  In a 20 gallon tank, fill the tank approximately until there is water just covering most of the bottom.
2. Add in a half cup to a cup of straight bleach.
3. Continue to fill the water tank until it is 3/4 full or so.
4. If your faucets come with filters in them, remove these filters so any large sediment that gets through the water pump filter will be expelled from the system.
5. Turn the water pump on and run the bleach/water mixture through the lines until the faucets begin to smell of bleach.  It may never smell like bleach - in that case, run the water long enough to feel comfortable that the mixture has gotten all the way to the faucets.
6. Leave the mixture in the system for 4-6 hours.
7. Open all of the faucets once again and run the faucets until the tank is empty.
8. Refill the tank to the top 2-3 times and pump it completely dry each time.  This will cycle fresh water through the system to get the bleach through.
9. Reattach your faucet filters, if you've removed them in step 4.
10. Enjoy fresh water for washing yourself (and the boat!).
11. Use it frequently to avoid having to shock the system again.

If your tank has been neglected and there is gunk in it or in the lines, you may have to engage a more serious treatment.  The most benign recommendation I have seen, in tanks that do not have an opening port through which you can get a physical scrubber, is to fill the tank with ice and then go for a bumpy ride.  The ice sliding around will chock up the bottom of the tank and lift away some of the sludge.  Then ensure that any faucet filters are removed before all of this stuff comes tumbling through your water lines.  If all else fails, you can try bleach and even white vinegar in the system, both of which will clean some of the sludge out in their own right.

West Marine and Amazon sell Thetford Fresh Water Tank Sanitizer among other brands (shocker - Amazon's is cheaper).  I have not personally tried these, but I have heard they are effective.  Beware of some tank cleaners, which do not have any actual cleansers but are simply aids to making water smell and taste better.

Since boating is primarily an activity for sunny days, make it a habit of carrying big jugs of water on board no matter what kind or size of boat you have.  At the very least, you'll have clean water to wash your hands, and at the very most you'll have life-saving fresh water in the event of serious dehydration.

Drink up, me hearties, yo ho!