leaking boiler

28 Jan 2005
Reaction score
United Kingdom
I have a Midas B wall mounted combi gas boiler which is dripping water from the safety relief valve.
It does this when the pressure reaches about 2 bar instead of 3 bar (according to the insructions) and stops dripping when the pressure drops below this.
Does this indicate a problem with the valve or something else.
Sponsored Links
It should operate at 3 bar but the fact that it does at 2 bar suggests it is faulty and needs renewing :(
Your system should be operating at around 1 bar, check your handbook.
2 bar is too high :eek:
It is set at about 1 bar and rises to 2 bar when central heating is on, and then
safety valve operates.
Sponsored Links
kevplumb said:
if the prv is opening at 2 bar replace it :rolleyes:

pressure rise depends on system volume :LOL:

Expansion vessel should match system volume, (10% percent off),
has anyone used the prv to drain the system recently? (lazy mans way) it could be dirt on the seating of the valve. turn the knob of the valve (usually anticlockwise) a few times, this might dislodge whatever is in there. if this doesnt work, then it will have to be a new valve.
always thought you were supposed to test prv with the service :oops:
You should test all safety systems at the annual service. If you service a boiler without making sure the user is safe, you come under the header ‘cowboy’ in my book.
A leaking prv is common and usually due to lack of inhibitor in the system, which has caused corrosion. Unfortunately for the user this means the need for a power flush in most cases as simply adding inhibitor at this point does not get rid of the accumulated debris.
If the pressure rises considerably when the system warms up the pressure in the compensation vessel is too low. Check if the diaphragm is okay and if so charge according to the manual.
Kev there are instances where the PRV will lift at around 2bar and still be sound. Send me an email- will give you more info.

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local

Sponsored Links