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Jeffrice
Jeffrice

Posted: Mon Nov 22, 2010 10:12am

Post Subject: Water Pump

Hi there, My water pump, the one that supplies the on-board taps from the water tank, activates about once per minute for about half a second. I've not found any sign of a leak in the system, so what else might cause this problem? In fact, I've had this problem for a while, but I've ignored it and now the pumps operation seems to becoming a little intermittent. Does this mean the pump has worn itself out? Jeff

Tony-B
Tony-B

Posted: Mon Nov 22, 2010 10:52am

Post Subject: Water Pump

I have no idea about the state of the pump but I do know there is a pressure loss somewhere. If you are sure there is no leak then locate the calorifier and somewhere around it there should be a pressure relief valve with a hose connection on the side which goes into the engien bilge or over the side. It has a plastic knob on top that turns easily but clicks as you turn it. With the pump turned on twist the knob a few times so the rush of water through the valve each time you twist it flushes any debris from the seat. If that does not sort it then I suspect the valves in the pump are leaking allowing pressure to leak back into the tank. The cheapest way to cure this is to fit a plumbers' flap type non-return valve between the tank and pump - or overhaul the existing pump/replace it. Trust this helps Tony Brooks

Jeffrice
Jeffrice

Posted: Wed Dec 01, 2010 9:03pm

Post Subject: Water Pump

Thanks Tony, The water pump has now packed up all together, so I'm guessing it's worn itself out. My thoughts were in line with yours, that water was leaking back through the pump into the tank. The pump's make is (was!) Whale. Before I replace the pump, can you recommend a brand that suffers the least from this problem? I think I'll fit a non-return valve at the same time anyway. And... just the right sort of weather for all this messin about! :) Jeff

Tony-B
Tony-B

Posted: Thu Dec 02, 2010 8:32am

Post Subject: Water Pump

Any of the major brands should be fine; Jabsco, Sureflow, Flojet etc. However I would not pay any extra money for one that altered its speed according to demand so it does not cycle and certainly I would avoid any with a bypass valve inside. which again is a cheap way of claiming the pumps do not cycle but in my view have an extra valve to fail. Tony Brooks

Jeffrice
Jeffrice

Posted: Fri Dec 03, 2010 9:09pm

Post Subject: Water Pump

Hi again Tony, My current pump (the broken one) has a pressure vessel fitted next to it. Do any of the pump brands you mention need a pressure vessel or have they got an internal pressure sensor that shuts the pump off once its up to pressure? Jeff

Tony-B
Tony-B

Posted: Sat Dec 04, 2010 7:52pm

Post Subject: Water Pump

All modern pumps came equipped with a pressure switch - as did your old one. The pressure vessel is either an accumulator or an expansion tank and it has nothing to do with switching the pump off. From its positions it is probably an accumulator which serves to decrease the pump cycling frequency and give far longer "off" periods when no water is being drawn. It should be pressurised (valve usually under the plastic "cap" thing) to about half the pump cut out pressure with no pressure in the system. The only thing you need to watch is that some of the bypass pumps (ITT Flojet I think) state they must not be used with an accumulator but the company has never given me a coherent explanation. I suspect that bypass pumps are made to save volume producers of boats having to buy an accumulator to minimise cycling. Tony Brooks


Posted: Tue Dec 07, 2010 3:15pm

Post Subject: Water Pump

Hi Tony, Just starting to dismantle... What does the accumulator do? Is it just an empty vessel to essentially create a bigger body of pressurised water in the system? I does have a valve on top, as you say. Looks a bit like a car tyre valve. Interesting. The make is VARUM. Jeff

Tony-B
Tony-B

Posted: Tue Dec 07, 2010 3:31pm

Post Subject: Water Pump

Ones with valves on have a diaphragm inside to separate the air from the water and they do exactly as you say. They are pressurised to about half the pump cut out pressure with the pump off and a tap open. Tony Brooks

Jeffrice
Jeffrice

Posted: Mon Dec 27, 2010 12:08pm

Post Subject: Water Pump

Hi Tony, Merry Christmas and happy new year! Thanks for your adive. I fitted a SHURflo pump. This did indeed cure the problem of the old water pump activiating every few minutes, idicating that the valves in the pump where the problem with water leaking back into the tank. As a point of interest, I did try to fix the old pump. Even though the pump had completely stopped working, once I'd dismantled it and manually massaged the valves, this freed the valves up and brought the pump back to life. I guess this could be that I'd been able to free dirt that was trapped in the valves. Jeff

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