Leaking Pressure Relief Valve

[DIYdabbler]

My Potterton Combi 80 boiler loses pressure quickly and I expect the reason for this is that water is currently constantly dripping out of the pressure relief pipe. Reading numerous posts on this forum I reach the conclusion that my Pressure Relief Valve needs replacing. This has been happening since I manually operated the PRV to reduce excessive pressure recently when it had reached 3.5 bar. This also leads me to think that the PRV is faulty in that it did not automatically open when the pressure went over 3 bar. I just turned the red cap on the PRV anti-clockwise a bit to manually open it - was this right?

I shall try to source a new PRV. Could you please advise if fitting the new one is just a matter of tightening the nuts firmly, or do I need to use some kind of sealant? Presumably I need to drain the boiler first too...?

I think I should also check my expansion vessel and possibly recharge it. I have an idea how to do this after reading some posts on the subject, but can I run this by you too please? Do I do the following:

- Empty the boiler of water (using the drain valve and not the PRV) and is this step essential? Also, any idea where this drain valve is on the Potterton Combi 80?
- Check the pressure in the expansion vessel using a car tyre gauge.
- Pump up the expansion vessel if necessary using a handheld pump, to about 1 bar (I think).

Hopefully I'm not too far off the mark but please put me right if I have got it wrong.

This is the first time I'm about to try home plumbing so any tips that will help me get it right first time will be greatly appreciated

Thanks,
Steve

 

[kevplumb]

1 yes you need to seal the joints when you renew the prv
2 if you want to drop the pressure in the boiler close the isolaters on the flow and return and use the prv BEFORE you change it

 

[DIYdabbler]

Thanks for your prompt reply.

Can you please tell me what this sealant is called and where I can get it from?

Is it essential to drop the pressure in the boiler to change the PRV and/or recharge the expansion vessel?

Thanks,
Steve

 

[kevplumb]

its essential if you want to check the ev pre charge
as for the prv if you dont you will get wet

 

[just-thinking]

combi 80 is a budget model of the puma.did anyone think the puma was a budget boiler ?

prv should never be manually opened as will probaly not re seal,
first buy a first aid kit.
second check expansion vessel charge.with car foot pump.boiler has to be de pressurised for this check as your prv is shot. only on this occasion open and leave prv open.pump up expansion vessel to 0.7 bar,its usuallu 0.5 bar but some charge will be lost during taking off foot pump connector.
inspect aav if any slight evidence of water leakage,change it now,get new swaling washer.
exchange prv.will need small allen key,a spanner for back not and a dab of non setting silocne grease.
re fill boiler to 1.5 bar.stand back and congrat your self.
open first aid box and stop fingers bleeding

 

[kevplumb]

you have obviosly been there m8

 

[croydoncorgi]

To reinforce the point...

On the Puma the Allen screws securing the PRV can seize. Worse, they're very small and the key can easily strip the head of the screw. If that happens, it's very difficult to fix! You may have turned the boiler into scrap in one twist of the wrist!

And yes, I HAVE 'been there' and spent quite a while removing the broken screw! Fortunately, it was the one I could get at.

 

[DIYdabbler]

Thanks for your replies so far. It seems my problem has got worse before I even had the chance to replace the PRV and recharge the expansion vessel. Maybe related to the pressure going too low, a noise was heard in one of the downstairs rads and then the boiler tripped the circuit breaker in the house. Now every time I try to turn the boiler back on, i.e. turn the central heating onto "constant", the circuit breaker trips immediately.

Looks like some kind of damage has been done, possibly as a result of the low pressure?

Anyone any ideas what might have happened and what I should try next?

Thanks,
Steve