Pressure release valve leaking

[Eloisec93]

Hey 

I have a pressure release valve on my calorifyer with a pipe that goes to the engine bilge.

It only leaks a drip every few seconds when the engine is running and heating up hot water in the calorifyer.

 

I have replaced the pressure release valve but the same thing happens. Drip by drip it fills up my engine bilge as the engine is on. When the engine is off no dripping 

 

I don't really understand has anyone got any advice or suggestions?

Edited November 23, 2021 by Eloisec93

[ditchcrawler]

If you have an accumulator on your hot water system it is not pressured correctly. The water is heating and expanding increasing the pressure that has to go somewhere 

[nicknorman]

10 minutes ago, Eloisec93 said:

Hey 

I have a pressure release valve on my calorifyer with a pipe that goes to the engine bilge.

It only leaks a drip every few seconds when the engine is running and heating up hot water in the calorifyer.

 

I have replaced the pressure release valve but the same thing happens. Drip by drip it fills up my engine bilge as the engine is on. When the engine is off no dripping 

 

I don't really understand has anyone got any advice or suggestions?

This is to be expected if you have no expansion vessel in the hot water system. Typically the cold feed to the calorifier goes via a non-return valve to the calorifier. So with all taps closed, water is effectively “trapped” in the calorifier. When you run the engine, this water gets heated and expands. With no-where for it to go (blocked by non-return valve and hot taps closed, pressure increases until the relief valve opens and water comes out to relieve the pressure.

 

Well this is the most likely explanation anyway. If that is correct, once the water in the calorifier gets up to temperature (after maybe an hour or so of engine running) water should stop coming out.

 

If you want to stop it, you need to install an expansion vessel that will absorb the expanding water without increasing the pressure too much. Fit it between the non-return valve and the calorifier input.

3 minutes ago, ditchcrawler said:

If you have an accumulator on your hot water system it is not pressured correctly. The water is heating and expanding increasing the pressure that has to go somewhere 

Yes this is another possibility, if there is no non-return valve fitted. Edit:or did you mean expansion vessel?

Edited November 23, 2021 by nicknorman

[PeterF]

11 hours ago, nicknorman said:

 

If you want to stop it, you need to install an expansion vessel that will absorb the expanding water without increasing the pressure too much. Fit it between the non-return valve and the calorifier input.

 

As that looks like a Surecal calorifier, the non return valve is integral in the manifold arrangement so Surecal recommend putting the expansion vessel on the warm outlet pipe. This prevents the dripping of the PRV but is not the ideal location.

[Tonka]

I have a pipe off of the prv which goes into a bucket. Then I simply empty the bucket every so often. 

[ditchcrawler]

1 minute ago, Tonka said:

I have a pipe off of the prv which goes into a bucket. Then I simply empty the bucket every so often. 

But every time it lifts it stresses you copper cylinder, far better to maintain the cylinder at a slightly lower constant pressure

[Tony Brooks]

2 minutes ago, Tonka said:

I have a pipe off of the prv which goes into a bucket. Then I simply empty the bucket every so often. 

 

But that does not mitigate the unnecessary repetative strain on the calorifier. As said in this and the OP's last topic, an expansion vessel is best practice.

[ditchcrawler]

15 hours ago, nicknorman said:

  expansion vessel

Edit:or did you mean expansion vessel?

That was the word that just wouldn't come into my head. I think Surecal warranty is nun and void without one 

[Tracy D'arth]

Its most likely a steel cylinder but continually letting  PRV dribble will erode the seat and need frequent replacement.  Fitting an expansion vessel to a hot pipe somewhere, it will cure the problem.

[blackrose]

15 hours ago, ditchcrawler said:

If you have an accumulator on your hot water system it is not pressured correctly. The water is heating and expanding increasing the pressure that has to go somewhere 

 

If there's a NRV in the system on the cold feed to the calorifier (as shown in the diagram above) then I don't think the accumulator settings will make any difference. There may not be a NRV of course in which case it would, but as others are saying best practice is to fit a hot water expansion vessel and set it correctly.

Edited November 24, 2021 by blackrose

[ditchcrawler]

4 minutes ago, blackrose said:

 

If there's a NRV in the system on the cold feed to the calorifier (as shown in the diagram above) then I don't think the accumulator settings will make any difference. There may not be a NRV of course in which case it would, but as others are saying best practice is to fit a hot water expansion vessel and set it correctly.

I slipped up and said Accumulator because I couldn't think of expansion but I did say on the hot water.

[Tracy D'arth]

47 minutes ago, ditchcrawler said:

I slipped up and said Accumulator because I couldn't think of expansion but I did say on the hot water.

Its OK, most of us knew what you meant.  Same vessel anyway, just fitted as you say on a hot pipe.

[blackrose]

23 hours ago, ditchcrawler said:

I slipped up and said Accumulator because I couldn't think of expansion but I did say on the hot water.

 

Ok I see. Some people without NRVs in their cold water supply to the calorifier rely on their accumulator tanks to accommodate the expansion of hot water so I misunderstood.