The Care And Feeding Of Your Boat's Water Systems

By Tom Neale
Published: April/May 2012

Boating is all about water, inside and outside your boat. So, let's take a close look at the maintenance tasks you'll need to carry out in order to stay on top of all your water systems, with loads of tried-and-true tips to keep everything clean and functioning well.

Illustration of a boat's water systems
Click to enlarge.

SEAWATER WASHING (1) Seawater systems such as anchor washdown and dishwashing with a seawater foot pump (if you're in clean water and rinse well with fresh potable water) can conserve water. Bathing in saltwater frequently causes skin problems in many people if done often. A freshwater rinse helps.

DRINKING WATER PURITY (2, 6) when in question, can be improved by addition of a small amount of bleach. The Washington State Department of Health recommends approximately 1 teaspoon of household bleach with no perfumes, dyes, or other additives per 10 gallons of water. See also the Centers For Disease Control site ( If possible, agitate the water after the addition of bleach and then let it sit for an hour. Chlorine odor will dissipate after a day. Bleach may initially make the water to which it's added unclear because it's killed the "bugs." The water clears as these settle to the bottom. They ultimately should be flushed out. It's preferable and safer to add product manufactured for the purpose; camping stores are good sources. If you have questionable water purity and no way to remedy it, boil water before drinking. Drinking-water filters such as GE's FXUVC under-the-sink cartridge remove many impurities and greatly improve taste. A water system UV light, such as those used in some reverse-osmosis systems, can kill viruses.

AIR CONDITIONING & REFRIGERATION (3) Condensation drain trays should be occasionally inspected to clear any blockage in drain hoses, which should preferably drain overboard rather than into the bilge. If trays don't drain fully, they'll develop a musty odor that will be circulated by the air handler.

ICEMAKERS (4) should be left open and off when not being used for a few days or longer to avoid odor and mold. Often the incoming water line is behind the unit in an area warmed by the unit, which facilitates stagnation and odor, particularly in the filter that may be in that area. When in use, the ice bin should be dumped at least every few days to keep water flowing. Good ventilation helps.

BILGE WATER (5) Oil-absorbent pads in bilges under the engine and whenever there's oil-spill potential are critical. They must not interfere with the operation of a bilge-pump float switch. Always clean loose fuel and oils out of the bilge with an oil-absorbent pad, and discard appropriately. Proper bilge-pump installation is critical and will vary with different boats. The hose interior should be smooth, the water column in the hose should be no more than needed, and great care must be taken to avoid backflooding from the sea. Visual and audible alarms are crucial.

Illustration of a basic bilge pump schematic
A basic bilge pump schematic.


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1. Anchor/foredeck washdown with pressure pump and foot switch.

2. Galley sink. Filter for cleaner cold water. Drains above waterline at max heel.

3. Air conditioning drip tray drains overboard above waterline at max heel.

4. Icemaker door open when not used.

5. Bilge pump drain well above water line on max heel. Smooth inner lining to hose. Vented loop may be needed if drain is near or below water line at max heel.

6. Head sink w/ filter on cold water and drain above waterline at max heel.

7. Shower sump pumped overboard to discharge above water line at max heel.

8. All thru-hulls equipped w/ sea cocks. Note double hose clamps.

9. Holding tank vented w/ minimum bends for better airflow.

10. Head discharges to MSD Type 1 w/ Y valve.

11. Holding tank has pumpout hose and gravity discharge overboard where legal.

12. Water heater has anti-backflow valve to prevent expanding hot water from entering coldwater system. (This tank is shown lying on its side, an installation seen on some boats. Normally, hot-water tanks are upright.)

13. Anti-siphon loops and valves.

14. Potable water tank w/ fill and vent.

15. Potable water tank has sediment filter prior to pressure pump.

16. Accumulation tank diminishes pulsation.

17. Solar shower bag

18. Scuppers drain cockpit. Some boats need scuppers w/ hose to discharge.

19. Jerry jug

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