Fresh Water Pump

[Hardy36]

I have a problem with my water pump taking a long time to switch off. I understand this is activated by a pressure switch. Does anyone know if the pressure is measured At the input or output of the pump

 

[QBhoy]

I have a problem with my water pump taking a long time to switch off. I understand this is activated by a pressure switch. Does anyone know if the pressure is measured At the input or output of the pump

Switch is usually contained in pump unit. Can get faulty, but I’d check you don’t have a leak somewhere too. Can often think it’s a pressure switch, when it turns out you have a leak or more commonly, your hot water tank relief valve is passing perhaps.

 

[ChromeDome]

Indeed. The pressure is measured on the pump outgoing side, to start the pump when pressure falls, normally because a tap is opened.
If pressure for any other reason goes below the threshold of the switch can't sense it properly, the pump will run on.

If the accumulator tank is defect the system will work as if there was no tank - unless the tank is leaking which would be visible and make the pump run as when a tap is open (because it so the pumps is the same loss of pressure = start pumping).

My deck wash pump pressure switch failed. Replaced with a universal, adjustable switch much like you see them on air compressors.

 

[superheat6k]

If your accumulator is one which is simply an open tank over time the air dissolves and the thing slowly fils with water. This can lead to excessive pump running, but it is easy to resolve. Turn the system off, disconnect the fill connection at the bottom of the accumulator rainout the water, also crask the top fitting to let air in, once its completely empty nip everything up and re-start.

I have had issues on a prior boat due to a gritty silt found in the FW tank that found its way into the pump and fouled the switch aperture.

If you need a new pump the Seaflo models on Ebay are excellent.

 

[Nito]

I had this the other day, pump continuously running. My water tank was low. Filled it up and problem went away. I surmised that a low tank level could make the pump think there is insufficient pressure and bring it on??! Perhaps I’m totally off the mark but it worked for me and hasn’t returned, yet!

 

[ChromeDome]

I had this the other day, pump continuously running. My water tank was low. Filled it up and problem went away. I surmised that a low tank level could make the pump think there is insufficient pressure and bring it on??! Perhaps I’m totally off the mark but it worked for me and hasn’t returned, yet!

Rather believe it sucked air in, pushed it out to side of the pump where pressure is measured and then couldn't build pressure because of the air acting as a damper.

 

[Nito]

Rather believe it sucked air in, pushed it out to side of the pump where pressure is measured and then couldn't build pressure because of the air acting as a damper.

Thanks, sounds perfectly plausible to me

 

[Hardy36]

Thank you so much for your input. I have suspected that there was an issue with the accumulator. As the taps spurt and vibrates when open. There is no visible leakage anywhere. Suspecting that issue was the accumulator I pumled an amount of air into the accumulator valve. When I ran the galley tap a brown light rust like colour came out for a few seconds. I haven’t seen this before. This morning I released all of the air from the accumulator and completely filled the water tank . The pump now switches of after just a few seconds but the tap when running spurts air violently …. could this be the accumulator or something else ? .. thanks for any thoughts …

 

[ChromeDome]

As your accumulator has a valve, you can pre load it with air the to a specified pressure. The water pump then will push and build pressure against the preload.

If said pre load disappears it must be either the membrane or the valve leaking. The valve usually is a common tyre valve type, with a replaceable/serviceable core.