Domestic water pressure

[LadyInBed]

On my domestic water system after the pump I have a pressure meter and accumulateor, then it splits to hot tank and cold taps, all fairly standard.When a tap is opened, the pump turns on about 3 secs after the tap is opened and off a couple of secs after the tap is shut, the pump turns on at 7psi and off at 16psi.
The accumulateor pressure appears to have no effect or influence on the water pressure no matter what pressure I put in it, I've tried pressures from ambient to 40psi. I would have expected the water pressure to reflect the accumulateor pressure, is that wrong? If not, could I have a blockage to the accumulateor?
When the system isn't being used, both pressures are maintained, so no leaks.
Can anyone throw some light or suggest a way forward.

 

[paulajayne]

Sounds like accum bladder is gone.

 

[No Regrets]

You might want to try using some Citric acid (harmless food grade powder you dissolve in hot water, and leave standing in the system for a week before flushing: Cost a fiver) to eradicate calcium build up.

While your 'problem' sounds like a very marginal issue, as many healthy systems operate thus, it could also be a poor quality feed to the input of the pump (The citric acid should clean up the entire tank and pipework anyway...) which needs a good feed for the pressure switch to operate properly.

Pump works if it's hitting 40psi, so my bet would be the switch. Of course I may be wrong!? :encouragement:

 

[pvb]

You should set the accumulator pressure to a couple of psi below the pump cut-in pressure, so in your case set the accumulator to 5psi.

If different pressures seem to make no difference, it's possible that the membrane is leaking internally - this wouldn't show up as a water leak.

 

[maby]

I don't think there will be any relationship between the water pressure and the accumulator pressure - the water pressure is controlled by the pressure sensor that is connected to the pump motor. Don't forget that an accumulator is an optional extra in a boat water system - many don't have one at all. The point of the accumulator is that water is not significantly compressible - which means that the pump will tend to cycle on and off rapidly if there is no accumulator. You apply power to the pump and it runs for a few seconds until the water pressure has risen above the cut-off pressure for the pump. When you next open a tap, the pressure in the system will drop rapidly and the pump will cut in, run for a short time until the pressure has been restored, the cut out again. This continues while the tap is open with the pump running in short spurts - noisy, annoying and the pressure fluctuations don't make for a comfortable shower!

The accumulator is just a balloon inserted into the water system - it contains air which is compressible and can take up some of the pressure fluctuations in your system. The water pump is still controlled by the same pressure switch and will work to keep the system pressure between two thresholds which are going to be the 7 and 16 psi. The pressure in your accumulator determines how much "give" there will be in it - pump it up to 40 psi and the 16 psi maximum in the water system will not be enough to compress the air much so the accumulator will have little effect. Equally, if you set the accumulator pressure very low, the water pressure will be enough to more or less collapse the balloon and the accumulator will have little effect. I would guess that the optimum pressure for the accumulator would be somewhere between the two extremes of your pump control switch - that should then allow the accumulator to expand and compress with the changes in water pressure and even out the flow.

 

[LadyInBed]

Sounds like accum bladder is gone.

Is that gone as in stiff as a board? As there are no leaks or bubbles in the water.

 

[vyv_cox]

Here is my method for setting up an accumulator. It will also tell you if yours is faulty.
Let all the air out of it. Turn on a tap. The pump will run continuously. Begin to pump air into the accumulator, the pump will run less and less frequently, until air pressure is too high, when it will run more frequently. Let air out slowly to maximise the 'off' period.

 

[LadyInBed]

Here is my method for setting up an accumulator. It will also tell you if yours is faulty.
Let all the air out of it. Turn on a tap. The pump will run continuously. Begin to pump air into the accumulator, the pump will run less and less frequently, until air pressure is too high, when it will run more frequently. Let air out slowly to maximise the 'off' period.

That sounds like a good ploy :encouragement:

 

[johnalison]

That sounds like a good ploy :encouragement:

I agree, but in the OP's case if the accumulator were not working I would expect the pump to turn off as soon as the tap is closed.

 

[paulajayne]

I agree, but in the OP's case if the accumulator were not working I would expect the pump to turn off as soon as the tap is closed.

It will run on until cut-off pressure is reached.

 

[vyv_cox]

I agree, but in the OP's case if the accumulator were not working I would expect the pump to turn off as soon as the tap is closed.

Yes, hence my earlier post. If the pump runs all the time the tap is open regardless of air in the accumulator, there is a problem with it.

 

[VicS]

On my domestic water system after the pump I have a pressure meter and accumulateor, then it splits to hot tank and cold taps, all fairly standard.When a tap is opened, the pump turns on about 3 secs after the tap is opened and off a couple of secs after the tap is shut, the pump turns on at 7psi and off at 16psi.
The accumulateor pressure appears to have no effect or influence on the water pressure no matter what pressure I put in it, I've tried pressures from ambient to 40psi. I would have expected the water pressure to reflect the accumulateor pressure, is that wrong? If not, could I have a blockage to the accumulateor?
When the system isn't being used, both pressures are maintained, so no leaks.
Can anyone throw some light or suggest a way forward.

So, what is the problem. Maybe the accumulator pressure is set a little on the low side but otherwise it seems to be workings satisfactorily.

To optimize the operation set the accumulator pressure to the pump cut in pressure or a little less. You should adjust the accumulator pressure with the pump switched off and a tap open to depressurize the water side.

Or you can try Vyv's more practical approach.

If the accumulator pressure is zero or above the pump cut out pressure it will be totally ineffective.

 

[LadyInBed]

Following Vyv's advice the pump stays off longest with the accumilator pressure set to about 10psi.
I was surprised that it's so low, unfortunately the meter on the air pump is too coures to get an exact reading (0-250psi) but my guess is that the optimum pressure is the mid point between the cut in and cut out pressure 11 - 12psi.
Thanks for all the suggestions.

 

[VicS]

Following Vyv's advice the pump stays off longest with the accumilator pressure set to about 10psi.
I was surprised that it's so low, unfortunately the meter on the air pump is too coures to get an exact reading (0-250psi) but my guess is that the optimum pressure is the mid point between the cut in and cut out pressure 11 - 12psi.
Thanks for all the suggestions.

Your accumulator doe's not have a schrader valve for the air that enables the use of your car tyre pressure gauge to check it ?

 

[PCUK]

You cannot adjust the water pressure coming out of the tap. The only pressure used in the system is to shut off the pump via the pressure operated switch. If you want more pressure of water from the tap you will need a more powerful pump. Other than that, your system is working perfectly.

 

[westhinder]

A related question if I may: I was surprised to find that my accumulator did not need to be pumped up. The manual says simply to open the valve so that ambient pressure can be achieved and then close the valve again. Does that sound right?

 

[Graham_Wright]

What does the membrane do in an accumulator? If it is mounted vertically, the air will provide the pressure without the membrane. Is it to do with contamination?

 

[johnalison]

A related question if I may: I was surprised to find that my accumulator did not need to be pumped up. The manual says simply to open the valve so that ambient pressure can be achieved and then close the valve again. Does that sound right?

There is/was a form of accumulator without a diaphragm. After a couple of failed diaphragms I bought one of the ones without diaphragm. With this sort, you open the valve, actually a removable cap, and effectively empty the accumulator of water before replacing the cap. The air is slowly absorbed during the season and the process needs to be repeated occasionally. This worked fine but the top with the cap was not strong enough for the tight-fitting cap and cracked, so I replaced it with a diaphragm type.

 

[vyv_cox]

I had a non-membrane type in a motorhome. Provided it was kept vertical it seemed to work OK. On the boat I have a membrane type and have not adjusted it for more than 10 years.

 

[maby]

What does the membrane do in an accumulator? If it is mounted vertically, the air will provide the pressure without the membrane. Is it to do with contamination?

The membrane is there to give you the option of not mounting it vertically. In a boat like ours, the water system is in the bilges and there is not enough height to mount a decent size accumulator vertically.