Accumulator tank pressure

[wiggy]

I've just fitted an accumulator to my water system. Having set the pressure according to the instructions I find that the water flow at the taps decreases to almost a dribble before the pump cuts back in, this seems to give an unsteady water temperature with the tap set to mix hot and cold.
What can I do with the accumulator pressure to encourage the pump to cut in earlier to stop the anoying loss in pressure before the pump cuts in and he water pressure resumes to a useful flow?

 

[sailorman]

I've just fitted an accumulator to my water system. Having set the pressure according to the instructions I find that the water flow at the taps decreases to almost a dribble before the pump cuts back in, this seems to give an unsteady water temperature with the tap set to mix hot and cold.
What can I do with the accumulator pressure to encourage the pump to cut in earlier to stop the anoying loss in pressure before the pump cuts in and he water pressure resumes to a useful flow?

1 bar i think, my jabsco has a schraeder (sp) valve, pressure it up with a cycle pump

 

[stuhaynes]

I've just fitted an accumulator to my water system. Having set the pressure according to the instructions I find that the water flow at the taps decreases to almost a dribble before the pump cuts back in, this seems to give an unsteady water temperature with the tap set to mix hot and cold.
What can I do with the accumulator pressure to encourage the pump to cut in earlier to stop the anoying loss in pressure before the pump cuts in and he water pressure resumes to a useful flow?

How big is the accumulator? I bought 2. First at .625 litres is utterly useless. The 2nd., when we fitted the calorifier, 5 litres. Spot on. We've not changed the little waste of time time yet, but when we do it'll be minimum 5 litres.

If this does not fit your parameters post your own system. Type of pump, operating pressure, size of accumulator. More info.

 

[wiggy]

It's a 25psi jabsco pump and 2litre jabsco accumulator tank.

 

[Mistroma]

It's a 25psi jabsco pump and 2litre jabsco accumulator tank.

Wouldn't be surprised if it isn't the same kit as my Jeanneau. I had a problem after a couple of years and the pump was cycling on & off very quickly when using water. It also stopped almost immediately after turning a tap off. That sounded like low pressure in the accumulator so I pumped it up with a bicycle pump as mentioned above. Problem solved and it went back to the normal longer cycle. I think the optimom pressure is usually around the pressure at the point the switch cuts in to start pumping.

Your symptoms don't sound the same so I don't think the acc. pressure is too low. I'm trying to think what would happen if the pressure was too high. It seems reasonable that if it was extremely high then the pump would cycle in a very small pressure range. Can't quite get my head around that behaviour but I don't think it would be as you described either (need to think about it overnight but it seems likely that it would also cycle rapidly on/off).

A 2 litre tank should be fine and a properly set accumulator or an under pressure one wouldn't give your symptoms. That only leaves an over pressure tank or something else.

Anyone else able to discount the over pressure tank? If so, then it might be restriction, pump or filter related.

 

[Keith-i]

Sounds like a lazy pressure switch in the pump. Having too much pressure in the accumulator would be akin to having no accumulator. Having too little pressure would just result in a 'holding' tank effect, neither of which would have much overall effect on the pressure at the tap. The accumulator does nothing for water pressure, it just provides a bit of a buffer to absorb and smooth out the pulses from the pump.

 

[david_bagshaw]

you need to set the differential pressure on the pressure switch.


some switches can be set at a cut in pressure and a cut out pressure

others a cut out pressure an a difference between cut in and out.

unfortuntely there are some that are just pre set, with no adjustment.

you either need to raise the cut in pressure, or reduce the differential pressure depending on the switch.

 

[oldfatgit]

When I had a similar problem, it was the pump not the accumulator. As stated above the accumulator should be set to a mid range pressure and that given in the manufacturers instructions is what it is designed to have. With an accumulator your pump should come a short on after a tap has been opened and stay on a while after as it charges up the accumulator. It there should be less pumping when the tap is turned on low and, perhaps for many the most important thing, not turn on in the middle of the night waking whoever sleeps nearest. Your pump needs to be man enough to charge up the accumulator and it is surprising how, by doing something to change a system, an older pump (no matter how good the make) will suddenly change how it is behaving.

 

[vyv_cox]

This method is foolproof, needs no gauges and takes about five minutes with minimal disruption.

Make sure your water tank has plenty of water in it. Discharge the air from the accumulator via the Schrader valve. Turn on a tap and listen to the rate of the pump stroke. Pump air into the accumulator with your bicycle pump, noting that the water pump rate will decrease, with longer pause periods. As you continue to pump air in the water pump rate will increase again. Let some air out until the rate is at a minimum. Turn off the tap and monitor the pump for a while. It should not stroke at all, if it does you have a leak or the pump suction valves have debris in them.

 

[wiggy]

Thanks for all the advice so far, the pump was new last year and as far as I know has no means f adjusting the pressure switch, I think I will go and experiment with the pressure in the accumulator and see if that will solve it, mind you I cant get my head around whether I need to add or subtract air. I feel a bit of faffing comming on.

 

[sailorman]

Thanks for all the advice so far, the pump was new last year and as far as I know has no means f adjusting the pressure switch, I think I will go and experiment with the pressure in the accumulator and see if that will solve it, mind you I cant get my head around whether I need to add or subtract air. I feel a bit of faffing comming on.

Vyv states " let the air out" then proceed with adjusting the pressure

 

[ccscott49]

Thanks for all the advice so far, the pump was new last year and as far as I know has no means f adjusting the pressure switch, I think I will go and experiment with the pressure in the accumulator and see if that will solve it, mind you I cant get my head around whether I need to add or subtract air. I feel a bit of faffing comming on.

Not the accumalator, it's the pump cut in pressure too low. The accumalator is but a dampener/pressure smoother to stop the pump continually pumping.

 

[wiggy]

Not the accumalator, it's the pump cut in pressure too low. The accumalator is but a dampener/pressure smoother to stop the pump continually pumping.

But the flow was fine before just juddery with the pump cycling.

 

[dougg]

Pump

Our pump is a Johnson pump and on the under side there is a tiny grub screw that alters the cut in/out pressure, sometimes this has sound itself out a couple of turns reducing the pressure of water at the taps etc.

 

[charles_reed]

Thanks for all the advice so far, the pump was new last year and as far as I know has no means f adjusting the pressure switch, I think I will go and experiment with the pressure in the accumulator and see if that will solve it, mind you I cant get my head around whether I need to add or subtract air. I feel a bit of faffing comming on.

Jabsco pumps have a preset, replaceable, pressure switch, screwed underneath the pump by the inlet/outlet pipes.
Having had considerable experience of accumulator tanks and their malfunctions I'd certainly recommend increasing the accumulator pressure - this varies from system to system but start @ 1.2bar and move up, as suggested by Vyv. If you get to 1.8bar with no improvement it is, possibly, the pressure switch. Do check for constrictions in both incoming and outgoing pipework.
I re-pressure my 2.5l jabsco accumulator every time I do a big engine service and re-pressurising has always resulted in improved and more regular flow.

 

[KellysEye]

>It's a 25psi jabsco pump and 2litre jabsco accumulator tank.

Make sure the sure the pressure in the tank is the same or slightly under 25psi. The tanks often come with 30 to 40lbs psi and you need to bleed them. If that doesn't work then the pressure switch is probably set wrong, it's adjusted by the screw on the front of the pressure switch. If that doesn't work then it might need a new pressure switch.

 

[Captainslt]

According to jabsco uk I was informed by telephone that the accumulator pressure should be 3 to 4 psi below the cutting pressure. So for a 20 psi cutting pressure you should have it set at 16 psi. In my case I’ve got a 40 psi Par Max 4 pump and I’ve been advised to set that to 16 psi as the cutting pressure for that particular pump. Hope this helps

 

[vyv_cox]

According to jabsco uk I was informed by telephone that the accumulator pressure should be 3 to 4 psi below the cutting pressure. So for a 20 psi cutting pressure you should have it set at 16 psi. In my case I’ve got a 40 psi Par Max 4 pump and I’ve been advised to set that to 16 psi as the cutting pressure for that particular pump. Hope this helps

Probably fixed now as the thread is nine years old.