Weird plumbing

[Blackfeather]

After our water tank seemed to empty itself too quickly on too many occasions, I was getting worried when the fresh water pump seemed to be cycling too frequently at the weekend.

As I filled up the tank again I noticed that one of the bilge pumps was emptying pretty rapidly. Cept I couldn't see which of the 3 pumps was running (and couldn't hear it). The water seemed to be coming from an outlet that I hadn't noticed running before. I also noticed, bizarrely, that the water was steaming. Bugger I thought, the hot water cylinder must have sprung a leak.

After contorting my not insubstantial frame into a space a gynecologist would have been proud to work in, I could see that the hot water cylinder was in tact and not leaking. It does however have a pressure release valve of some sort on top which was attached to the guilty outlet. It had a red knob on top which could be turned anti clockwise and clicked. It also said '3 bar' on it. I turned it but the water kept flowing.

In the end I pinched the outlet pipe with a cable tie sufficiently to stem the water flow but, hopefully, not tight enough to prevent any real pressure blow off.

I struggle to believe that the fresh water pump, which is 5 years old, could really build up sufficient pressure to force water out through this release valve so I am guessing it is the valve itself which is at fault.

Does anyone have any similar experience? Also is it likely that the valve could be replaced in isolation rather than the whole cylinder/calorifier?

Any help gratefully received.

 

[puddock]

Not an uncommon problem. The relief valve may have a small piece of debris preventing it from closing completely. Functioning the red knob (opening/ closing) may be enough to flush whatever is lodged there, out.
Failing that, you can remove it (maybe strip, clean and reassemble it if it allows). If this is not an option or does not solve the problem, take it along to the local plumber/ heating supplies store and buy a replacement - not expensive (@£15 if I remember correctly).

The increase in pressure is likely to be a result of expansion in the heated water rather than your water pump.

 

[Sandyman]

Agree with puddock.

Have you got an expansion cylinder ?

 

[NormanS]

You are recommended to operate the valve, manually, every month or so.

 

[PCUK]

If the system doesn't have an accumulator tank to act as an expansion vessel then the expanding hot water will easily blow the relief valve.

 

[Blackfeather]

Thanks to all. As usual, invaluable information, it makes much more sense now.

 

[David2452]

Console yourself that at least your calorifier PRV was installed properly with the outlet through a skin fitting rather than the usual dump into the bilge arrangement!
PRVs are as cheap as chips, (about £8.50 for retail the normal 3 bar type), just replace it and then operate it by spinning it every month or so, it really isn't worth trying to fix them at the price if a simple spin to blow any calcium lodged under the seat doesn't work. I normally fit a pressure gauge in potable water and heating systems so owners can monitor faults, again cheap at less than a tenner and worth doing at the same time.