If you have a combi boiler and it shoots water out the overflow pipe when you try to pressurise/fill the system, does that suggest that a diaphragm in the expansion vessel may be ruptured? Also if so, can this be fixed or is it an unit replacement jobbie?

Cheers

D

What pressure is showing on the gauge when the water discharges as this will lead to the problem, and what make is the boiler.

Mog

He says he cant pressurise it back up Mog - overflows straight away. Make is a Valiant. Thanks for your advice!

The relief valve is designed to open up at 3.5 bar, so the gauge should show that at least before it discharges. If the expansion vessel has gone you would be able to fill the system up as normal but as soon as the boiler heated the water the vessel would'nt take up the expansion in the water and the pressure would rise up 3.5 bar and then discharge. If you are not able to put any water into the system then it sounds like a dodgy relief valve with possibly some crap caught in the seating.

Mog

Sounds to me like someone has drained the system using the saftey valve(pressure relief)!! A very bad way to do it(cowboy way), as ****e in the system gets caught on the seating and keeps it open.

Fit a new one and see if you have a problem ,they are only about £10 and as the system is drained then it wont take very long..

Dunc

Thanks chaps - that all makes sense. New pressure relief valve it is then.

post up your boiler details and I will try to find the cost and part no.s for you.

Mog

Thanks for the offer Mog. With your and my advice he was confident enough to discuss it with a few plumbers and found one decent chap to fix it (and his dodgy water flow sensor switch I diagnosed) for £60 + parts. Very reasonable I thought.

Edit - the diaphragm was mush, causing the pressure relief valve to stick open - diaphragm only replaced.

[Edited by Diesel - 9/12/2003 1:57:37 PM]