Noisy waterworks

[Hippohay]

The fresh water pump's doing my head in. Went down at the weekend to find it going off every 45 seconds or so for a few seconds - even tho no tap etc was open or dripping. There's a basic 1-litre Jabsco accumulator tank which was full to top with water. I emptied the accumulator tank and the pump then kicked in every 5 minutes or so. But, after a few days, the intervals did seem to be getting shorter and shorter.
What's going on? Is the accumulator tank not doing its job (the pump kicks in immediately a tap's opened - I thought an accumulator tank was intended to prevent this for a few seconds)?
Would a beefier accumulator tank - where its air pressure could be set - improve matters?
Or does it simply have to be a leak in the system somewhere?
Any help appreciated.

 

[Norman_E]

The problem is usually caused by water flowing back through the pump when it is switched off due to a non-return valve not seating properly. I expect your pump has a non return valve inside it which you could either clean or replace (though I have not seen the internals of one), but sometimes the best cure is to fit a separate non return valve between pump and accumulator. As your accumulator filled itself with water it may have a small leak or porosity which has allowed the air to escape even though water does not leak out.

 

[FAITIRA]

Hi, have had the same prob, before I fitted a partical filter before the pump, tiny bits of "stuff" get under the valves in the pump, resulting in water leaking back and the pump presure switch cutting in.
Try putting in a filter, if you don,t have one, before the pump, clean the valves, and as N_E suggests, a non return BEFORE the pump would be a help. This is all assuming you don,t have a leak in the system after the pump of course.

 

[johnphilip]

If the accumulator is filling it must be leaking. I had to take one back last year after only a few months use. The screw cap on the top was a tight fit and actually split the neck of the bottle. the more you tightened it the worse it became.

 

[Hippohay]

Hi - ta for advice. Just to check: Norman E suggested a non-return valve between pump and accumulator, you seemed to agree but then suggested putting the valve before the pump. Am confused! Where should it go?

 

[Danny]

Most pumps have three or four little valves inside them that are one way in operation and open and close in sequence. This is the 'ticking' you can hear. If one is leaking then the pressurised water in the piping after the pump can leak back through the pump. This triggers the pressure switch so the pump runs again to build up the pressure - and this cycle repeats over and over and.....

It can be caused by a bit of dirt in one of the valves or it may be a broken valve or diaphragm. A pump service kit and, if not already installed, a filter before the pump should sort it out.

 

[Norman_E]

My own setup has a non return valve between pump and accumulator, but one before the pump would work just as well, if not better. I had forgotten about filters but my own boat has about 4 of them in various places, and the ones between the tanks and the pump certainly do catch quite a bit of stuff. I do not know if this applies to the filters fitted to boats, but I have seen a design with a spring loaded valve which opens when the filter becomes clogged, in order to protect the pump. If you do have a filter, clean it out and make sure that the gauze is intact.
Another thought is that even when you have sorted out the pump valves, and checked the accumulator for any leak, there is something else to look at. On most pumps you can adjust the pressure switch to set how much pressure there should be at the pump switch on and switch off points. Make sure the difference is not too small, as that can lead to the pump "short cycling".

 

[FAITIRA]

Sorry, to have the desired effect, I think it should go between the pump and the tank, ie on the suction side, then a filter between the valve and the tank to prevent bits holding the non return open.

 

[VicS]

[ QUOTE ]
Sorry, to have the desired effect, I think it should go between the pump and the tank

[/ QUOTE ] Yes that is right at least the important fact is that it must go before the pressure switch. Assuming that is part of the pump assembly then the valve must go between tank and pump. If it were put after the pump (and pressure switch) then pressure could still leak back to the tank and cause the pump to cycle. However it is only really a fudge to get around the need to service or maybe just clean the valves in the pump. If there is dirt getting through then it is only time before some gets lodged in this extra valve and you are back to square one.

A filter is essential. the only pump I am familiar with (a Jabsco, I think) says on it that a filter must be used! But it is only a strainer, nothing fancy.

 

[Hippohay]

Many thanks all for advice. I'll give cleaning valves etc in pump a go. There's a filter between the main water tank and pump, so I'll clean that too. Still think there must be summat up with the accumulator tank - I'll check if there's a crack near the air vent at the top. After that, grrr...

 

[VicS]

[ QUOTE ]
Still think there must be summat up with the accumulator tank

[/ QUOTE ] Can you disconnect the accumulator and blank off the connection to check your theory. The system should still work without it but the pump will cut in and out more frequently while you are drawing water at less than full flow.

 

[FAITIRA]

Sounds like the pump leaking back through the valves to me, you would see evidence of a leak at the accumulator otherwise. Carefully check the filter gauze is intact too.