Accumulator tank woes

[longy]

Ok so I fitted an accumulator tank a few months ago and recently the water system has been acting odd. At present the tank is full but the water pump keeps making a sporadic clunking sound 

 

Ive checked the tank and when pressed air does come out of the valve.

 

Ive altered the pressure switch both increased and decreased but I cannot get the sporadic pump noise to stop, probably clunks every 15mins or so. Ive checked for leaks where I can but cannot see any

 

Ive taken the tank pressure to 25psi (par max 4 pump has a kick in of 15psi) pump turned off drained the water out and then turned back on.

In theory the pump shouldnt start as its way above the parameters but mine kicked in. Am I correct in thinking the pressure switch is knackered or am I missing something

 

As always all advice welcome

 

• BTW When I increase or decrease the pressure switch screw it does increase or decrease the pressurebut I dont know how or where it reads the 10psi cut in from

Edited July 17, 2023 by longy
wrong psi cut in

[DaveR]

The instructions that came with my accumulator:

 

At what pressure should I set the accumulator tank?
The pressure in the tank is adjusted by means of the air valve in the closed end.
The tank is supplied with an internal pressure of about 2.8 bar (35 psi). Reduce this pressure to
2 - 3 psi below the cut-in pressure of the pump (refer to pump instructions for details). This pressure adjustment is best done before installation of the tank, using a car-type pressure gauge to determine when the required pressure is reached, as follows:
i. Depress the central pin of the Schrader valve with your finger, to release gas
ii. Release gas a little at a time, until the pressure is correct
iii. If you release too much gas by mistake, air may be pumped back in with a hand - or foot-pump.
WARNING
Make sure that there is adequate ventilation when setting or adjusting pressure in an accumulator tank. Nitrogen is non-toxic, but oxygen levels may be reduced in confined spaces.
If the tank pressure requires adjustment after installation, ensure first that the pump is switched off and that an outlet is open, so that there is no pressure in the system. Then regulate the pressure as indicated above.
Check the accumulator tank performance in this way every 6 months, and adjust the pressure if necessary.
 

EXAMPLE
Pump Cut-in     Acc. Tank Pressure Pressure setting
1 bar (15 psi) 0.8 bar (12 psi)
0.7 bar (10 psi) 0.5 bar (7 psi)
0.5 bar ( 7 psi) 0.3 bar (5 psi)

[longy]

But what if I set the tank to its original 35psi and then turn the pump back on (it shouldnt activate like it didnt when i first installed it) but what if the pump kicks in does this indicate that the tank has failed or the pump pressure switch has failed

[Tracy D'arth]

5 minutes ago, carp-addict said:

But what if I set the tank to its original 35psi and then turn the pump back on (it shouldnt activate like it didnt when i first installed it) but what if the pump kicks in does this indicate that the tank has failed or the pump pressure switch has failed

It does not indicate that the accumulator is flat. As long as the pump runs on a bit after you close the tap and you get some water before the pump cuts in it is fine.

 

If the water pressure from the pump is dropping without having a tap open you either have a leak or the pump valves are letting water back to the tank.  To establish which, shut the stop valve on the tank outlet.  If the pump is still occasionally running then, you have a leak that you have not found ---- yet!

 It is not the way that the switch in the pump normally plays up.

 

I set the accumulator air pressure by pumping it up, letting the pump work and closing the tap. Then carefully releasing air until the pump just cuts in. Job done.

[longy]

Update I have pumped the tank back to 35psi and slowly let the pressure out like Tracy advised last time. It seemed like an age of releasing the pressure but eventually the pump kicked in. Refilled the tank but I am still getting the sporadic pump sound. I turned off the stop valve on the water tank and the pump sound has stopped.

 

So am I right in thinking theres no leak on the system and its the pump valves, in this case can they be replaced or is it easier to fit a new pump

 

 

[Tony Brooks]

32 minutes ago, carp-addict said:

Update I have pumped the tank back to 35psi and slowly let the pressure out like Tracy advised last time. It seemed like an age of releasing the pressure but eventually the pump kicked in. Refilled the tank but I am still getting the sporadic pump sound. I turned off the stop valve on the water tank and the pump sound has stopped.

 

So am I right in thinking theres no leak on the system and its the pump valves, in this case can they be replaced or is it easier to fit a new pump

 

 

 

Almost certainly, yes. If you don't want to fit a new pump, then putting a correctly orientated plumbers flap valve between pump and tank is likely to solve the issue. Better still between inlet strainer and pump.

[longy]

1 minute ago, Tony Brooks said:

 

Almost certainly, yes. If you don't want to fit a new pump, then putting a correctly orientated plumbers flap valve between pump and tank is likely to solve the issue. Better still between inlet strainer and pump.

Thanks 

In the meantime using the system as is with the pump clonking now and then is this pressurising the system or just going back and forward

1 hour ago, Tracy D'arth said:

It does not indicate that the accumulator is flat. As long as the pump runs on a bit after you close the tap and you get some water before the pump cuts in it is fine.

 

If the water pressure from the pump is dropping without having a tap open you either have a leak or the pump valves are letting water back to the tank.  To establish which, shut the stop valve on the tank outlet.  If the pump is still occasionally running then, you have a leak that you have not found ---- yet!

 It is not the way that the switch in the pump normally plays up.

 

I set the accumulator air pressure by pumping it up, letting the pump work and closing the tap. Then carefully releasing air until the pump just cuts in. Job done.

Thanks Tracy

1 hour ago, DaveR said:

The instructions that came with my accumulator:

 

At what pressure should I set the accumulator tank?
The pressure in the tank is adjusted by means of the air valve in the closed end.
The tank is supplied with an internal pressure of about 2.8 bar (35 psi). Reduce this pressure to
2 - 3 psi below the cut-in pressure of the pump (refer to pump instructions for details). This pressure adjustment is best done before installation of the tank, using a car-type pressure gauge to determine when the required pressure is reached, as follows:
i. Depress the central pin of the Schrader valve with your finger, to release gas
ii. Release gas a little at a time, until the pressure is correct
iii. If you release too much gas by mistake, air may be pumped back in with a hand - or foot-pump.
WARNING
Make sure that there is adequate ventilation when setting or adjusting pressure in an accumulator tank. Nitrogen is non-toxic, but oxygen levels may be reduced in confined spaces.
If the tank pressure requires adjustment after installation, ensure first that the pump is switched off and that an outlet is open, so that there is no pressure in the system. Then regulate the pressure as indicated above.
Check the accumulator tank performance in this way every 6 months, and adjust the pressure if necessary.
 

EXAMPLE
Pump Cut-in     Acc. Tank Pressure Pressure setting
1 bar (15 psi) 0.8 bar (12 psi)
0.7 bar (10 psi) 0.5 bar (7 psi)
0.5 bar ( 7 psi) 0.3 bar (5 psi)

Thanks Dave

[Tony Brooks]

5 minutes ago, carp-addict said:

Thanks 

In the meantime using the system as is with the pump clonking now and then is this pressurising the system or just going back and forward

 

It is pressurising it until the pump cuts out and the pressure gradually leaks back into the water tank until the pressure drops until the pump cuts in again.

 

However, I am not happy with the word "clonk". Normally the pressure has to drop a fair way if you have a correctly pressurised accumulator, so the pump actually runs for some seconds or longer to refill the accumulator. The word clonk suggests it does not much more than make one revolution, and such short run time is usually typical of having an over pressurised or no accumulator, but you have one, and it seems it is correctly pressurised.

 

Edited to add, to stop the clonking, only turn the pump on when drawing water. That is why I usually fit a switch in the galley and toilet compartment.

Edited July 17, 2023 by Tony Brooks

[longy]

Maybe the wording wasn't ideal. It sounds like a single pump revolution 

[Tony Brooks]

1 minute ago, carp-addict said:

Maybe the wording wasn't ideal. It sounds like a single pump revolution 

 

What capacity is the accumulator. A small one will refill with les pump revolutions than a large one. I think NBs typically use about five litre accumulators, not that it matters much.

[longy]

So am I right in thinking the accumulator tank is pushing water back through the water pump and into the water tank.

5l only been fitted in the last 6 months or so

[Tony Brooks]

1 minute ago, carp-addict said:

So am I right in thinking the accumulator tank is pushing water back through the water pump and into the water tank.

5l only been fitted in the last 6 months or so

 

Yes, correct, but with a five litre tank I would have expected more than a short clonk. Still proof of pud and all that, If the valve or a new pump solves it then it must be back leakage.

[Tracy D'arth]

QUOTE.

" I turned off the stop valve on the water tank and the pump sound has stopped. "

 

So it has to be back flow.

[longy]

20 minutes ago, Tony Brooks said:

 

Yes, correct, but with a five litre tank I would have expected more than a short clonk. Still proof of pud and all that, If the valve or a new pump solves it then it must be back leakage.

Ive had the water tank stop valve switched off for 30 mins and upon putting the valve on there was a short burst from the pump

 

[Tony Brooks]

13 minutes ago, carp-addict said:

Ive had the water tank stop valve switched off for 30 mins and upon putting the valve on there was a short burst from the pump

 

 

You see that is different from a "clonk" and is much what I would expect with a leaking valve.

[longy]

👍 cheers Tony

 

I will update once Ive changed the pump over

[Tony Brooks]

32 minutes ago, Tracy D'arth said:

QUOTE.

" I turned off the stop valve on the water tank and the pump sound has stopped. "

 

So it has to be back flow.

 

I would agree but it is that word clonk. To my mind, it does not describe what normally happens in that situation. The new words "short burst from the pump" does. I wanted clarification before being definite.

[ditchcrawler]

It sounds to me as if the OP has a check valve on the discharge side of his pump so would only need a dribble to run back before the pump did one click to represurise it.

Another way to test that the accumulator is somewhere near the right pressure is to bring the system to full pressure, ie. the pump cuts out and then see how much water you can get from the cold tap before the pump starts again running it into a kettle or something.

[Tracy D'arth]

7 minutes ago, ditchcrawler said:

It sounds to me as if the OP has a check valve on the discharge side of his pump so would only need a dribble to run back before the pump did one click to represurise it.

Another way to test that the accumulator is somewhere near the right pressure is to bring the system to full pressure, ie. the pump cuts out and then see how much water you can get from the cold tap before the pump starts again running it into a kettle or something.

An idea but quantify?  How much would you expect from a 5 ltr accumulator?  Its a lot less than 5ltrs depending on the ratio of pump pressure to air pressure. I would expect no more than 1.5 ltrs.

Its backflow on the pump, shutting the stop tap proves it.

[ditchcrawler]

4 minutes ago, Tracy D'arth said:

An idea but quantify?  How much would you expect from a 5 ltr accumulator?  Its a lot less than 5ltrs depending on the ratio of pump pressure to air pressure. I would expect no more than 1.5 ltrs.

Its backflow on the pump, shutting the stop tap proves it.

I fully agree with the backflow but it should need half an accumulator full to flow back before switching and then run for a few second to recharge the accumulator, not just a blip of the pump.
 

I would expect between 1.5 and 2 lts depending on how its pressured of course, ether over or under pressurising it would lead to a lot less water coming from the tap. I would also do the test on both hot and cold, one after the other in case the accumulator has been connected after a check valve  that's there to stop hot water feeding back.

I hope the OP does mean the accumulator and not the hot water expansion vessel.

[Tony Brooks]

19 minutes ago, ditchcrawler said:

It sounds to me as if the OP has a check valve on the discharge side of his pump so would only need a dribble to run back before the pump did one click to represurise it.

 

 

That makes sense, but why would anyone do that. Waste of a check valve to my way of thinking. If you are correct, then he could change the side of the pump it is on for little effort and no money.

[ditchcrawler]

23 minutes ago, Tony Brooks said:

 

That makes sense, but why would anyone do that. Waste of a check valve to my way of thinking. If you are correct, then he could change the side of the pump it is on for little effort and no money.

As I replied to Tracy that when fitting it it got connected after the check vale that stops the hot water back feeding, we could even be talking about an expansion tank

[Tony Brooks]

1 minute ago, ditchcrawler said:

As I replied to Tracy that when fitting it it got connected after the check vale that stops the hot water back feeding, we could even be talking about an expansion tank

 

Agreed. So now we need to know where about in the system and on the boat the "accumulator" is situated. I think you may be right about the expansion tank, it makes much more sense.

[longy]

5 hours ago, Tony Brooks said:

 

Agreed. So now we need to know where about in the system and on the boat the "accumulator" is situated. I think you may be right about the expansion tank, it makes much more sense.

The tank is literally next to the water pump and the main water tank. At the other end of the boat I have a calorifier tank and another accumulator tank 

[Tony Brooks]

Thanks, so not an expansion vessel.