Leaking Pressure Relief Valve

westhinder

westhinder

Well-Known Member
Joined
15 Feb 2003
Messages
2,658
Location
Belgium
Visit site
The PRV on my water heater has developed an annoying leak, which causes the pump to cycle far too often.
Any ideas what I could do? Would soaking it in vinegar help?
Or should I just condemn and replace it? If so, can I use a spare that I buy at the plumbers?
 
westhinder said:
The PRV on my water heater has developed an annoying leak, which causes the pump to cycle far too often.
Any ideas what I could do? Would soaking it in vinegar help?
Or should I just condemn and replace it? If so, can I use a spare that I buy at the plumbers?
Click to expand...

It may be a temperature and pressure relief valve.

If you replace it you will need to get one with the same pressure (and temperature) ratings
 
Last edited:
You are supposed to turn the relief knob occasionally - when I fitted a new one as old was leaking the instructions on the new one said monthly, to keep the valve face clean. This is on a temp and pressure valve from ASAP.
 
westhinder said:
The PRV on my water heater has developed an annoying leak, which causes the pump to cycle far too often.
Any ideas what I could do? Would soaking it in vinegar help?
Or should I just condemn and replace it? If so, can I use a spare that I buy at the plumbers?
Click to expand...

It depends why it is leaking. If might be faulty, it might also be releasing excessive pressure as intended. A spare must have the same pressure ( and possibly temperature as mentioned) specification as the original to be safe, but in principle you can buy a spare at the plumbers merchants. Don't be tempted to fit one with a different rating. Some of these PRVS can be dismantled and the seating cleaned and sprung diaphragm examined for damage. It depends which one as not all of them come apart.
 
PRV's aren't expensive, so as mentioned above if its a standard type you can get a spare at many plumber's merchants. (Not worth trying to fix). Pick one that operates above the upper (cut-out) pressure of your pump, bearing in mind the safety limit of your calorifier. If you have a 40 psi pump and a 37 psi PRV - yes, it's going to leak!

While it could be the PRV itself, it is just as likely to be a problem with the pump. I've known them getting considerably above their rated cut-out pressure. With the popular Jabsco type there is a pressure adjustment screw which you might experiment with - see the manual.

Also check your expansion tank. The symptom of low pressure there is a very jerky cut in and out of the pump which puts an extra load on both the pump and the PRV, often resulting in leaks and pump failure. If the expansion tank isn't working at all, then when water is heated and expands in the calorifier it has nowhere to go except out through the PRV. The expansion tank should be pressured to just below the cut-in pump pressure. Expansion tanks do need replacing from time to time.

Finally, do you have a non-return valve fitted to your hot water system? This is quite common. If so you must also have an accumulator (secondary expansion tank) fitted and working next to the calorifier to cope with water expansion. The accumulator should be pressured above the cut-out pressure of the pump but below that of the PRV.

P.S. The temperature sensor of the PRV, if you have one, is a bit of a luxury, and these are anyway often unreliable. It is OK to use a replacement without one.
 
Last edited:
Thank you all for your advice.
I will check the cut out pressure on the pump that i replaced last year, and look for a new PRV with the correct specifications. At nearly 20 years of age I suppose replacing it is in order.
 
The actual valve costs about a fiver. :D When I wanted to replace mine last winter, I found that it also incorporated a drain screw. I thought that seemed like a good idea, but couldn't get an exact replacement, so fitted a Tee piece with a drain cock between the PRV and the calorifier. It makes it easy to drain the calorifier to protect from winter frost damage.
 
You must log in or register to reply here.

Share this page

Top