Jabsco fresh water pump 'blipping'

[rogerthebodger]

I think you have a leak in the inlet valve of the pressure pump. This would cause the pressure pump to cycle as you describe. It could also cause a small increase in pressure in the feed from the tank that could cause a dribble to pass through the foot pump and exit the foot pump open faucet.

 

[temptress]

Edit?!

edited - my phone died!!!!

 

[temptress]

Yes OK, I suppose it's not strictly 'in parallel' although I suppose you could argue that water following either route ends up in the same place - the sink plug ole!

There is a calorifier but it is connected to the pressure side of the Jabsco. It has it's own pressure relief valve into the bilge.

I'm thinking of trying two courses of action:

1. Block off the footpump feed. If the Jabsco is pressurising it's feed then the excess pressure will go back to the tank i.e. no effective difference. If there IS a difference, then the footpump valves must be at fault.

2. Fit a non-return valve immediately prior to the Jabsco.

Are you getting air into the system? If not forget the foot-pump and check the pressure relief valve on the hot water tank you may find it is leaking, they often crud up. As you have a hot water system you really should have an accumulator fitted on the pressure side. As the water heats and cools in the system the pressure varies and this can cause pressure loss in all sorts of places - an accumulator will smooth this out. Jabsco have a good explanation on their website.

IMO the issue will be somewhere on the 'pressure' side of the system. The pump will suck air/water or whatever it can form the inlet side but only when the pressure switch detects a drop in pressure. The instruction manual for the pump model will give you the tolerances. If the cutoff pressure is very close to the safety valve pressure this will cause what you are experiencing.

 

[NormanS]

The system, particularly if there is hot water, would be improved by the addition of an accumulator, but as has been suggested already several times, the cycling symptoms almost certainly point to a valve passing water within the pump. I would check there, before thinking about adding extra NRVs, or anything else.

 

[VicS]

The system, particularly if there is hot water, would be improved by the addition of an accumulator, but as has been suggested already several times, the cycling symptoms almost certainly point to a valve passing water within the pump. I would check there, before thinking about adding extra NRVs, or anything else.

Absolutely if there really are no leaks but the calorifier was not mentioned earlier! Worth a check on the relief valve in case a leak there has been overlooked.

 

[temptress]

Absolutely if there really are no leaks but the calorifier was not mentioned earlier! Worth a check on the relief valve in case a leak there has been overlooked.

It may not even be obvious - the pressure relief valve may simply be weeping hot air or gas (steam) - if the tolerances are close then it would only take a few 'drops' to cause the pressure pump to cycle. How old is the boat? The newer jabsco pumps work at higher pressure than some of the older ones.

 

[Graham_Wright]

Yes OK, I suppose it's not strictly 'in parallel' although I suppose you could argue that water following either route ends up in the same place - the sink plug ole!

There is a calorifier but it is connected to the pressure side of the Jabsco. It has it's own pressure relief valve into the bilge.

I'm thinking of trying two courses of action:

1. Block off the footpump feed. If the Jabsco is pressurising it's feed then the excess pressure will go back to the tank i.e. no effective difference. If there IS a difference, then the footpump valves must be at fault.

2. Fit a non-return valve immediately prior to the Jabsco.

I'm not really keeping up with this but my problem was solved by fitting a N/R valve on the outlet of the foot pump.

 

[Carduelis]

I understand the well-made points about accumulators and calorifiers, but just to be clear, the boat is thirteen years old and this is a 'new' problem.

There is no leak from the calorifier pressure relief valve. It was one of the many places I have looked. Even if it was, the calorifier is on the pressure side so it wouldn't explain the simultaneous dribble from the faucet surely?

 

[sailorman]

I understand the well-made points about accumulators and calorifiers, but just to be clear, the boat is thirteen years old and this is a 'new' problem.

There is no leak from the calorifier pressure relief valve. It was one of the many places I have looked. Even if it was, the calorifier is on the pressure side so it wouldn't explain the simultaneous dribble from the faucet surely?

Have you checked "The Keel"

 

[temptress]

I still think the foot pump dribble is irrelevant back pressure from the pump pulling water into itself. If you are sure of the integrity of the pressure side then it can only be one of the seals on the pump. I believe Jabsco offer a 5 year warranty so if you have the receipt get the pump replaced by them.

I would also replace the 13 year old pressure relief valve_they only cost a few quid...

GOOD LUCK

 

[VicS]

I still think the foot pump dribble is irrelevant back pressure from the pump pulling water into itself. If you are sure of the integrity of the pressure side then it can only be one of the seals on the pump. I believe Jabsco offer a 5 year warranty so if you have the receipt get the pump replaced by them.

I would also replace the 13 year old pressure relief valve_they only cost a few quid...

GOOD LUCK

Seals ???

 

[temptress]

Typo valves or even an O ring but I still think there's a leak somewhere.

 

[jon711]

Now where to start....

1, The dribble on the manual pump should not be related to the pressure side of the system, but, you say it dribbles when the pressure pump cycles?

2, If the electric pressure pump has been fitted into a calorifier system, without an accumulator tank, then there could be a possibility that when the hot water has expanded, pressure has been put on the valves in the pump causing wear and eventual failure. If these internal valves were in a flooded suction environment the drop off in performance would not have been noticed, but, the pump would be very reluctant to prime.

3, So lets assume, the internal pump valves are worn (ie not sealing/closing correctly), they would allow a water path back into the downstream section of the pipework, and the water would take the easiest escape route (through the manual pump?), thereby reducing the pressure on the pressure switch and causing the pump too cycle. (Some yachts have non return valves fitted in or near the tank outlet)

4, So, my suggestion would be to replace valve set on the pump (it could just be that a small bit of gunk has got into the valve set causing an incorrect seal, you should really have in inline filter fitted prior to the pump to reduce the chances of this), fit an accumulator tank on the pressure side of the electric pump, fit new seals/valves in the manual. It sounds as if all the issues have accumulated (excuse the pun), and increased the issue.

Jon