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Pressurizing your freshwater system

Q: Why won’t your freshwater system repressurize after it has been emptied?

A: With spring approaching, many of you soon will be taking your boats out of winter storage. Among the host of recommissioning chores to address is the freshwater system, and sometimes the system doesn’t pressurize after layup. The pump just keeps running.

First, be sure your pump is pumping. After winter storage its valves may have stiffened to the point that they don’t seal well, particularly if the pump isn’t new. This prevents the pump from sucking the water out of the tank and up through the feed pipe to the pump. The longer the run between the water in your supply tank and the pump, the more important it is that the valves seal tightly. (Be sure your tank is full before doing any of this.)

If you’re familiar with the sound of your pump, you may be able to hear it running too fast, indicating that it’s not sucking water. A relatively low amperage draw by the pump also may indicate this. To be sure, disconnect the hose from the output side of your pump, then turn on the pump. If nothing comes out, this is a good indication of a bad pump.

Most pump manufacturers sell valve assembly replacement kits that are fairly easy to install. I wouldn’t buy a freshwater supply pump that didn’t have this easy valve replacement feature. Replacing those valves (or fixing whatever else is wrong with the pump) should hopefully do the trick.

If the pump is working well, the problem may be that you didn’t vent your water heater when you turned the pump back on. When a water system is drained for the winter, usually the water heater also is drained (it should be). Unless you bleed it when you get it up and running again, you’ll have a large amount of air trapped in the top of the heater.

Your water pump has a pressure switch that starts and stops the pump as it senses the pressure in the water line. When the pressure is high enough, the pump will cut out. Air is much less dense than water. If there is a large air pocket, the pressure may not get high enough at the sensor, and the pump may keep running long enough to burn out or cause an overheat shutdown.

Fortunately this is usually an easy fix. You can bleed the air out of the top of the tank simply by opening all your faucets when you turn on your freshwater pressure pump. This is what you should do anyway, for both the hot and cold sides. The pump then should be able to push out this air and any other air in the system. When water is running freely from the faucets with no more bubbles, close them and the pump should cut out as the pressure reaches its set point.

If this doesn’t work, try disconnecting the hose from the output of the water heater (should be near the top). Then turn on your water pressure pump. If it’s working, it should pump water into the heater (displacing the air pocket), and eventually water should start coming out that outlet port. Reconnect the hose, open the faucets, and run the pump until no bubbles come out. Turn the faucets off and see if the pump stops running.

Some systems also may develop an air lock somewhere in the plumbing downstream of the pump. As strange as it seems, a small pocket of air can cause a blockage in water flow if it occurs in just the right (or should I say wrong?) place in the line. This doesn’t usually happen, but if your boat’s like mine, it’ll mess with you any way it can.

You can get rid of an air lock by disconnecting the plumbing at various places downstream of the pump and turning the pump on until water flows freely from each successive disconnect. Eventually you’ll remove the air pocket. Be sure to wear a bathing suit when you do this; you’ll probably need one.

A note about safety: Before disconnecting the hot water line, be sure the water isn’t hot. The heater shouldn’t be turned on until you have freely running water, the tank is full, and all work is completed. Disconnect all electricity to your water heater and other systems. When working with plumbing and the pump, use extreme caution to see that nothing dangerous is in the area. For example, if you opened a connection and water flooded out onto a hot electrical line, you could be electrocuted. When you turn on your pump to test, you should be in a safe area even though the pump is probably DC. If you don’t have an adequate level of skill and understanding, have a qualified professional do this work.