Leak in water pipe?

[XLD]

Hi my water pump has started firing up for 1 second every 12 seconds. The pressure vessel is 3 years old. The pump fires up now as soon as l turn the tap on. I cant find any leaks in the pipework. Is there any other possible cause or must there be a leak somewhere?

 

[Onewheeler]

Accumulator needs repressurising (or replacing if the bladder has sprung a leak).

[David Mack]

Or water is leaking back through the pump.

Turn off the main valve on the tank outlet. If the pump no longer keeps firing up that would confirm it is water leaking back through the pump. The cause is most likely some dirt in the pump valves.

Edited July 6, 2024 by David Mack

[Onewheeler]

2 hours ago, David Mack said:

Or water is leaking back through the pump.

Turn off the main valve on the tank outlet. If the pump no longer keeps firing up that would confirm it is water leaking back through the pump. The cause is most likely some dirt in the pump valves.

That's the easiest and quickest to check.

[Jen-in-Wellies]

1 hour ago, Onewheeler said:

That's the easiest and quickest to check.

If the pump is leaking back to the tank, a simple check valve installed in the pipe from the tank will stop it happening. Had to do this once. Saved having to replace, or attempt a repair on the pump.

[Onewheeler]

31 minutes ago, Jen-in-Wellies said:

If the pump is leaking back to the tank, a simple check valve installed in the pipe from the tank will stop it happening. Had to do this once. Saved having to replace, or attempt a repair on the pump.

Maybe need to use a little caution: if there's a plastic strainer on the pump inlet I'm not sure it would take the full pressure of the pump, which it would be exposed to if the pump were leaking backwards. I don't know what the spec of those strainers is but they don't look very robust.

[Jen-in-Wellies]

8 minutes ago, Onewheeler said:

Maybe need to use a little caution: if there's a plastic strainer on the pump inlet I'm not sure it would take the full pressure of the pump, which it would be exposed to if the pump were leaking backwards. I don't know what the spec of those strainers is but they don't look very robust.

Downstream of the strainer and before the pump is a good idea for a check valve location anyway, as there it stops grit getting in to the valve seat. The Jabsco strainer was happy with backflowed pump pressure on the one I did. Three bar isn't a great deal of pressure.

[XLD]

23 hours ago, David Mack said:

Or water is leaking back through the pump.

Turn off the main valve on the tank outlet. If the pump no longer keeps firing up that would confirm it is water leaking back through the pump. The cause is most likely some dirt in the pump valves.

Thanks.Tried that, but pump still cycling. So hopefully, accumulator just needs repressurisng

 

23 hours ago, Onewheeler said:

Accumulator needs repressurising (or replacing if the bladder has sprung a leak).

Well l've repressurised the accumulator tank up to 2 bar. (It was low). That's the same cut out pressure as on the Whale Watermaster FW1214(B) model. Ran the pump with water tank valve both on and off. Still cycling intermitantly when on and running constantly when off. 

Pump sounds dog rough. 

Time for a new pump???

[Iain_S]

Accumulator should be pump cut in pressure, not cut out.

 

[Jen-in-Wellies]

25 minutes ago, XLD said:

Time for a new pump???

Not yet. If it isn't leaking backwards, then there is a leak somewhere else. Do you have a calorifier? If so, check for any dripping from the pressure relief valve. On some boats, the outlet from this might go to a bottle, on others to the bilge, on others to a skin fitting and overboard. If it's not that, then go through each and every pipework joint.

[Tony Brooks]

Cycling one second on and two seconds off does nor sound like an accumulator pressure problem to me unless it is either zero or at or above cut out pressure, but even if that were the case it would still need a leak to drop the pressure from cut-out to cut-in in 12 seconds.

 

Has the PRV on the system had its knob twisted a few times with the pump on, so hopefully any scale has been washed from the valve. Also, is the PRV spring in good order - assess by the difficulty in twisting as you compress the spring. I have taken note of the claim that the back leakage from pump valves and a plumbing or tap washer leak has been checked.

 

Pumps do sound rough when the inlet is fully or partially blocked, but that should result in a longer period before the pump cuts out.

 

Jen posted while i was typing.

Edited July 7, 2024 by Tony Brooks

[Onewheeler]

5 hours ago, Jen-in-Wellies said:

Not yet. If it isn't leaking backwards, then there is a leak somewhere else. Do you have a calorifier? If so, check for any dripping from the pressure relief valve. On some boats, the outlet from this might go to a bottle, on others to the bilge, on others to a skin fitting and overboard. If it's not that, then go through each and every pipework joint.

A long shot, but if a defective prv vented back to the cold water tank it would explain the behaviour. I think it has been done!

[XLD]

On 06/07/2024 at 13:43, David Mack said:

Or water is leaking back through the pump.

Turn off the main valve on the tank outlet. If the pump no longer keeps firing up that would confirm it is water leaking back through the pump. The cause is most likely some dirt in the pump valves.

Thanks.Tried that, but pump still cycling. So hopefully, accumulator just needs repressurisng

 

On 06/07/2024 at 13:34, Onewheeler said:

Accumulator needs repressurising (or replacing if the bladder has sprung a leak).

Well l've repressurised the accumulator tank up to 2 bar. (It was low). That's the same cut out pressure as on the Whale Watermaster FW1214(B) model. Ran the pump with water tank valve both on and off. Still cycling intermitantly when on and running constantly when off. 

Pump sounds dog rough. 

Time for a new pump???

New pump (always carry a spare) , same problem. Next check PRV🤞

New pump (always carry a spare) , same problem. Next check PRV🤞

[Tony Brooks]

25 minutes ago, XLD said:

Thanks.Tried that, but pump still cycling. So hopefully, accumulator just needs repressurisng

 

Well l've repressurised the accumulator tank up to 2 bar. (It was low). That's the same cut out pressure as on the Whale Watermaster FW1214(B) model. Ran the pump with water tank valve both on and off. Still cycling intermitantly when on and running constantly when off. 

Pump sounds dog rough. 

Time for a new pump???

New pump (always carry a spare) , same problem. Next check PRV🤞

New pump (always carry a spare) , same problem. Next check PRV🤞

 

 

[XLD]

Put another pump on. Sorted. Now post mortem on the old one.

[MtB]

21 hours ago, XLD said:

Thanks.Tried that, but pump still cycling. So hopefully, accumulator just needs repressurisng

 

No, the accumulator pressure will only affect the length of time between pump blipping on briefly. You have 12 seconds now, and that will go up to maybe a minute or three once you get the pressure set right, depending on the capacity of the accumulator.

 

But the pump will still keep running from time to time as it needs to replace the water leaking out of the system. 

 

My money is on the calorifier PRV letting by and going out of the boat via a skin fitting.

 

 

 

 

[XLD]

9 minutes ago, MtB said:

 

No, the accumulator pressure will only affect the length of time between pump blipping on briefly. You have 12 seconds now, and that will go up to maybe a minute or three once you get the pressure set right, depending on the capacity of the accumulator.

 

But the pump will still keep running from time to time as it needs to replace the water leaking out of the system. 

 

My money is on the calorifier PRV letting by and going out of the boat via a skin fitting.

 

 

 

 

No the new pump solved the problem👍

[MtB]

1 minute ago, XLD said:

No the new pump solved the problem👍

 

In that case it was backflow into the tank all along. 

 

Excellent you have it fixed now! 

 

[Tony Brooks]

6 minutes ago, MtB said:

 

In that case it was backflow into the tank all along. 

 

Excellent you have it fixed now! 

 

 

I suspect that the tank shut off valve is a gate (wheel) valve, which are known not to seal when they get on a bit.

 

If it is, the OP would be well advised to fit a quality lever valve.

[blackrose]

On 07/07/2024 at 18:34, Onewheeler said:

A long shot, but if a defective prv vented back to the cold water tank it would explain the behaviour. I think it has been done!

 

How does a PRV on a calorifier vent to the cold water tank? Sounds like an unusual set up.

 

Or were you talking about the NRV on the cold water feed pipe to the calorifier?

Edited July 9, 2024 by blackrose

[Momac]

On 08/07/2024 at 15:00, XLD said:

Put another pump on. Sorted. Now post mortem on the old one.

Folks say it's not worth trying to fix water pumps but a clean out and maybe some O rings could sort it out.

 

.

[blackrose]

3 minutes ago, Momac said:

Folks say it's not worth trying to fix water pumps but a clean out and maybe some O rings could sort it out.

 

 

It's worth it if you can fix it easily and keep it as a spare.

 

I fixed a water pump which was sucking in air with a bit of sealant. It works perfectly now and I kept it as a spare. I'm glad I didn't chuck it away.

Edited July 9, 2024 by blackrose

[Tony Brooks]

26 minutes ago, blackrose said:

 

How does a PRV on a calorifier vent to the cold water tank? Sounds like an unusual set up.

 

Or were you talking about the NRV on the cold water feed pipe to the calorifier?

 

The PRV can be immediately downstream from the pump, PROVIDING there is no NRV in the hot feed to the calorifier. . Then it is just a short length of pipe from the PRV outlet to the pump inlet. Unusual, yes, but it allows the pump, PRV, pressure switch, pressure gauge, and NRV on the pump inlet and accumulator to be mounted on a board with a couple of easy to release pipe fittings. Then all the vulnerable parts can be lifted out and taken home for the winter to protect from frost damage,

 

 

[blackrose]

14 hours ago, Tony Brooks said:

 

The PRV can be immediately downstream from the pump, PROVIDING there is no NRV in the hot feed to the calorifier. . Then it is just a short length of pipe from the PRV outlet to the pump inlet. Unusual, yes, but it allows the pump, PRV, pressure switch, pressure gauge, and NRV on the pump inlet and accumulator to be mounted on a board with a couple of easy to release pipe fittings. Then all the vulnerable parts can be lifted out and taken home for the winter to protect from frost damage,

 

 

 

Ok I see, I thought they were always mounted on the calorifier itself, but I guess there are other ways of doing it. No NRV on the cold feed to the calorifier has always seemed like a bad idea to me though. Why would anyone want to heat up a cold water pipe? As well as being wasteful couldn't Legionalla be an issue somewhere down that pipe that's always warmish? I've no idea but just a thought. The only downside of a NRV on the cold feed pipe just before the calorifier is that it means you should also have a hot water expansion vessel so that you're not solely relying on the PRV - which would also be a waste of hot water because it will constantly dribble.

[Tony Brooks]

12 minutes ago, blackrose said:

 

Ok I see, I thought they were always mounted on the calorifier itself, but I guess there are other ways of doing it. No NRV on the cold feed to the calorifier has always seemed like a bad idea to me though. Why would anyone want to heat up a cold water pipe? As well as being wasteful couldn't Legionalla be an issue somewhere down that pipe that's always warmish? I've no idea but just a thought. The only downside of a NRV on the cold feed pipe just before the calorifier is that it means you should also have a hot water expansion vessel so that you're not solely relying on the PRV - which would also be a waste of hot water because it will constantly dribble.

 

Why would the cold feed to the calorifier heat up, if the accumulator is also acting as an expansion vessel, for more than a meter or so, and as the bottom of the calorifier is normally the coldest part, why should legionella be a major problem. One's domestic cold water tank in the loft at home probably gets warmer in hot sunny weather.