dripping pressure valve on calorifier

Yep, they do get crud in them, by turning the red knobby bit you can sometimes clear the obstruction, otherwise get another one, they are fairly cheap.

Apparently, turning the knob every now and then makes them last longer. FC is the expert on them.
 
Turning the knob makes a clicky noise. That's lifting the valve and should clean it. If not, you can get a replacement for less than a tenner from a plumbers merchants.
 
When I replaced mine I used one with a pressure gauge connection to which I fitted a 1/4" ball valve, flexi airline hose and air jet blower nozzle. Brilliant for washing down the engines and bilges with hot water straight from the calorifier.
 
Have you checked the accumulator/expansion vessel? If it doesn't have any precharge or the membrane is ripped then you will get exactly that, a dripping PRV everytime the cylinder heats up and you said "drips occasionally".

Or does it constantly drip, even if the cylinder is cold? That would be the valve.
Good luck,
Findus
 
Phoenix of Hamble said:
No, can't say I have checked it... it is an occasional drip, and only when hot, so i'll take a bicycle pump with me, and give the pre charge a check!
Click to expand...

Make sure, that the hot water side of the expansion vessel is not under pressure when you check the precharge. Switch the water pump off, open a hot water tap and then check. 99% sure, that it is the vessel and not the PRV.
Good luck!
Findus
 
It's usually a case of change the PRV. It's possible to clean them with limescale remover, but then the problem usually returns fairly soon.

Otherwise, as Findus says, a failed or wrongly pressured expansion tank is the likely cause (or accumulator tank if no expansion tank is fitted). It may not have ruptured, they do tend to lose pressure over time, the problem may be cured with a few pumps. Don't overdo the bicycle pump though as an over-pressured expansion tank will be just as bad as an empty one. Use a pressure gauge to test the pressure in the tank.

In the past I've had two rather more dangerous causes of a leaky PRV. On one occasion I found the dripping PRV was being caused by a Jabsco water pump delivering way over its rated pressure. On another by failure of the calorifier thermostat so that the water was getting far too hot - practically boiling. So if the new PRV also drips, don't ignore it but check all of these.
 
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findus said:
Have you checked the accumulator/expansion vessel? If it doesn't have any precharge or the membrane is ripped then you will get exactly that, a dripping PRV everytime the cylinder heats up and you said "drips occasionally".

Or does it constantly drip, even if the cylinder is cold? That would be the valve.
Good luck,
Findus
Click to expand...
Top marks Findus... you were spot on!.... there was little or no pressure in the accumulator, so I stuck a pump on it, and took it to 1 bar... bingo... leak has vanished!

Thanks for your advice.
 
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