Boiler pressure goes too low...what's a pressure relief valve?

helping_hubby

Hi,

The last month or 2 we've had to increase the pressure on the boiler twice because it got too low and cut out.

I've been googling and it suggests a leak. We did have a drip from a radiator but that was before this happened and we fixed that.

I came across a thread where it said it could be the "pressure relief valve". Can someone explain what this means?

Excuse my ignorance, but I know nothing about boilers...
We have a pipe that runs outside and I've noticed that this drips a fair bit. Is this something that can cause the pressure to drop? Or is that normal?

roddydogs

That is the pressure release valve outlet. Is it a "Combi"?

helping_hubby

Yes it's a combi.

david29dpo

It does sound like the valve it leaking slightly. Some boilers have a knob on the valve to release excess pressure manually. It may be worth increasing the pressure to about 2 par and then opening the valve to release the pressure back to 1 par. Sometimes this reseats the valve better.

gas4you

What boiler do you have and how old is it?

It could just be the prv spring has become weak with old age and letting by. It could however be another fault and the prv is just doing its job.

What is your pressure reading when the prv is dripping?

helping_hubby

gas4you wrote: »

What boiler do you have and how old is it?

It could just be the prv spring has become weak with old age and letting by. It could however be another fault and the prv is just doing its job.

What is your pressure reading when the prv is dripping?

It's less than 18 month old. It's a potterton, can't remember exact model. We've been doing a lot of DIY, including removing radiators etc. Would draining the system and starting over help? I think we need to get some inhibitor in there anyway.

BritRael

helping_hubby wrote: »

...I came across a thread where it said it could be the "pressure relief valve". Can someone explain what this means?...

A pressure relief valve is a safety device installed into pipes to prevent damage by over-pressurisation.
If the pressure in the system increases and the pre-set pressure is reached, it opens to allow the pressure to drop to a safe level.

BritRael

david29dpo wrote: »

...It may be worth increasing the pressure to about 2 par and then opening the valve to release the pressure back to 1 par....

That should read 'bar', not 'par'.

Tucker

I had this on an my last boiler and after doing some work on a radiator, the hose to the expansion tank got blocked and the pressure was building up too high and sending water out of the release valve.

I sorted the blockage and within a week, the release valve went and was releasing water at 1.5bar instead of 3 bar.

Mind you it was a rubbish BG boiler. Every engineer I spoke to told me to get rid of it..... I did in the end, £300 too late though.

Tucker

helping_hubby wrote: »

It's less than 18 month old. It's a potterton, can't remember exact model. We've been doing a lot of DIY, including removing radiators etc. Would draining the system and starting over help? I think we need to get some inhibitor in there anyway.

Try B&Q. They are selling off some 1 litre tubs in the clearance section for a £1 a tub. Each tub is enough to treat your complete system.

gas4you

What is your pressure reading when the prv is dripping?