Getting the water out

Apr 4, 2014

(page 3 of 3)

Systems should be designed so that check valves are not needed as these can cause as much as a 50 percent reduction in the pump capacity. Check valves can also become a clogging problem.

An electrical terminal block mounted too low and not sealed from water.

If the discharge is below the heeled waterline, the hose must be looped above the waterline and a vented loop installed to prevent back siphoning. Each pump should have its own discharge thru-hull as well; never tee two or more pumps to the same outlet. Pickup hoses should have a screen or strainer on the bilge end that is easily accessible for cleaning. Try to pick a screen that is coarse enough to catch larger particles, but not so fine that it clogs too easily. Without a doubt the biggest reason pumps fail is ingesting trash. Hair in particular is a problem for all pumps. “Every owner should clean and paint their bilges white once a year so they can see how dirty their bilges are,” said Keene. “Pump clogging is a major issue with all types of pumps.”

For electric pumps the wiring is critical as well. Any electrical connections that could get wet should be made as waterproof as possible. Heat shrink tubing is the best, but makes replacing parts and trouble shooting a bit more difficult. Terminal strips are better for replacement and troubleshooting, but harder to get watertight. Whatever method used, the connections need to be checked occasionally.

A double-chamber manual diaphragm pump mounted in the cockpit.

One of the biggest wiring errors in bilge pump installations is using undersized wires. Bilge pump capacity is rated with 13.6 volts, so unless your engine is running and charging the batteries your pumps are likely to be running at a lower voltage. Voltage drop from undersized wiring can further reduce the power to the pump. A #12 wire is the smallest that should be used for all but the smallest pumps. The further from the power supply, the larger the wire needed to avoid voltage drop. With the pump running under load, check the voltage at the power source and then at the pump. If the drop is more than three to five percent, the wire size should be increased. If your electric pumps have an automatic switch, they should be wired so that power to the switch cannot be turned off accidentally.

It should be kept in mind that any dewatering system is primarily for removing water once any leaks have been found and corrected. The first line of defense is knowing you have a leak and quickly correcting it. Bilge pumps can buy time while repairing leaks, but should never be counted on to keep the boat afloat with a leak, even a small leak can quickly outpace most pump capacities. The better your pump system is and the more efficient it is the more time you will have to correct any leaks. Keep the boat’s bilges clean and always test pumps under load prior to any offshore passages.

Capt. Wayne Canning lives on his Irwin 40 Vayu, in Wilmington, N.C. A marine professional for more than 35 years he is now a full-time marine surveyor, freelance writer, and consultant/project manager. Canning also runs websites for those restoring project boats. Visit and for more info.

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