Washdown Pump Installation

Washdown pumps are becoming more and more popular, especially on fishing boats, where they make cleanup almost a pleasure. And they aren’t difficult to install. The heart of any washdown system is, of course, the pump. Wander down the aisles of any boat store and you will see a wide variety of washdown pumps. Many are simply relabeled freshwater pumps. Washdown pumps are often three- or four-chambered diaphragm pumps driven by a 12-volt DC motor, and are typically rated to deliver 2.8 to 5 gallons per minute (gpm). They come equipped with a pressure switch that turns the pump on when the pressure in the delivery hose falls below about 45 pounds per square inch (psi). Less commonly used are belt-driven diaphragm pumps and flexible impeller pumps. Be sure to check the duty rating of the pump motor. Freshwater system pumps are designed to turn on, pump water for a short period of time, and then shut off. Your washdown pump, on the other hand, may have to run for a long period of time while you sluice your decks. If not rated for continuous duty, the pump motor could overheat.

The higher the pump’s pressure rating, the more forceful the stream it produces and the better job it can do cleaning your boat. Some pumps specifically designed for washdown systems are rated as high as 70 psi. The West Marine model #7865678 pump, for example, is rated at 3.4 gpm at 70 psi and is equipped with five diaphragm chambers and five valves, resulting in less pulsation in the output supply. It also has a built-in water strainer. Many manufacturers supply washdown pumps as part of a kit that also includes hose fittings, a spiral hose, and a hose nozzle. Make sure the kit has the components you are interested in, or else buy the components separately. Other things a washdown system will need are a source of water, power for the pump motor, and a means of delivering the water to the right place.

While diaphragm pumps are pretty good about handling small amounts of debris, a water strainer is needed to keep the big chunks out. If your pump isn’t fitted with a strainer, you’ll need to install one. It should be rigidly mounted to a bulkhead or stringer so it doesn’t move around and chafe the hoses. If you mount it above the waterline, you will be able to clean it out without having to close the seacock to which it is connected. The seacock should be part of a dedicated through-hull fitting below the waterline. You may be tempted to tee into another water inlet line, say the water supply for flushing the head or an engine coolant intake line. This usually isn’t a good idea, however, as the throughhull flow rate might not be sufficient to supply both systems.The pump should be mounted to a bulkhead or other vertical surface above the waterline, and its plumbed end should face down to prevent any water leaks from running down into the motor. Fasten it securely with stainless steel machine screws and nylock nuts, which are locking nuts with a nylon insert to keep them from loosening.

Next comes the wiring. The pump needs a source of 12-volt DC power. Wiring must be properly sized for the amperage being drawn and for the distance between the pump and its power source. Refer to wire sizing charts available online and in catalogs like West Marine’s. A fuse or circuit breaker must be installed in the power supply line. A circuit breaker provides a convenient means of turning the system off, whereas if you use a fuse instead, you’ll have to place an on/off switch in the circuit. To connect the power supply to the pump motor wires, use butt connectors with adhesive-lined heat-shrink tubing for a strong watertight connection. For physical protection, I like to run the wires in a conduit or at least inside spiral wrap, and fasten the wires to something solid on the boat’s structure every 18 inches or so with wire clamps.

The pump outlet can be plumbed to as many locations as you want, but remember that the pump will be able to supply adequate pressure to only one outlet at a time. One method is simply to connect a hose from the pump outlet directly to the garden hose and nozzle you will use. Although this works, it does limit the usefulness of the system. A better approach is to plumb two or more different locations—for example, one in the stern for cleaning up fish goo and another in the bow for washing down the anchor rode. Clear reinforced vinyl tubing is fine for this application. You can identify the reinforced version by the white spiraled threads embedded in the vinyl. Hose fittings may be either the quick-release type or those with standard garden hose threads.The latter can be found with or without shutoff valves, and they look remarkably like the ones on the side of your house. Spigots that protrude from the cockpit wall can be real ankle-biters, so I prefer recessed units. If you choose a garden faucet style of fitting, make sure to locate it where it won’t endanger the crew’s ankles. Support the supply lines every 18 inches to avoid chafing. Quick-release fittings for washdown systems can be disconnected while the system is under pressure. These can accept standard garden hose or the spiral coiled washdown hose. I avoid the spiral hose despite—or maybe because of—how well it retracts. Once you let go of this type of hose, it snaps back to where you got it. Call me old-fashioned, but I prefer to drag a regular garden hose around the deck. The other good thing about a garden hose is that many styles of nozzles are available for it. Stay away from high-volume nozzles if you have a lower-rated pump. Water tends to just dribble out of such nozzles when they’re not supplied with sufficient flow or pressure.