Water pump question

[fox islander]

When at the slip, hooked up to shore power, with all fixtures closed the water pump turns on every 10-15 mins or so, and runs for maybe 1/2 a second.
When away from the slip, with DC power only, the pump will turn on every 15-20 seconds and run for about a second. Very annoying, so of course we have to turn the pump off at the panel.
Anyone have any ideas what could cause this?

Thanks in advance.

 

[gpd955]

Sounds like you either have a leak or air is getting into your system causing the pump to prime. Check all of your hose clamps and hoses as well as all of your fixtures. If air is getting in it will cause that. You can have air getting in with no water leaking out so don't just look for water.

 

[Stu Jackson]

Yup

 

[Roger Long]

You can have air getting in with no water leaking out so don't just look for water.

How, if the system is pressurized?

You may not find water and may not be able to stop the problem though. A fresh water pressure pump is essentially two one way check valves with a chamber in between which the motor makes larger and smaller by pumping a diaphragm (most common) or a piston up and down. There is a pressure switch downstream of the second one way valve. The water pressure slightly inflates all the hoses in the system. When you turn on a faucet, the pressure is relieved and the pump turns on.

If the valves in the FW pressure pump are leaking slightly, the back flow can relieve the pressure by sending a very small amount of water back to the water tank. The pressure switch will then trip and the pump will run. If you have debris in the tank such a sediment or paint chips, the problem can be intermittent. A bit of something will lodge in one of the valves and let it leak. Next time you run a substantial amount of water, it may seal tight again.

If you can't find water leaking from any of the fittings or a faucet leaking and the cycling is continuous, you may need to buy a new pump unless it is one that can be overhauled.

 

[fox islander]

Thanks for the advice...I'll check clamps, hoses and fixtures...still not sure why the pump runs so much more when not connected to shore power. [scratches head].

 

[Old Skool Neil]

Roger's description is exactly what happened with my original pump and its first replacement, internal check valve leak down. My solution was to get rid of the Shur-Flo style pump and go with the Holy Grail of pumps, the PAR belt driven 36900 Series.

 

[Stu Jackson]

Sometimes it's from an almost empty water tank, pump will actually run continuously.

Shorepower should have nothing to do with it, it's a 12V DC pump. I agree, is puzzling.

 

[newboatowner]

I had the same problem and found water in the port settee in cabin under the cushion and in a storage area. I could not understand where this water was coming from and I looked behind the toilet inside the hull and found a tee that was leaking waster under pressure. I tightened the hose clamps (3) and, voila, the leak stopped, the water did not gather in the hold and the pump stopped turning on and off.

Good luck.

 

[BillyK]

could be different when on shore power due to the higher voltage you have while the battery charger has you over 12 volts. that's all that would be different. the higher voltage basically causes the pump to put a higher pressure on the downstream hoses so it leaks down longer.. on the batteries it may not pressurize as much and the leak down takes less time.

 

[fox islander]

Thanks for the suggestions....still havent found a leak yet but still looking.