Hi Guys,

Been having problems with my boiler losing pressure for the past week. I have determined it is probably my expansion vessel.

Would the following be a good way to determine if I have a faulty expansion vessel:

1. Power down Boiler
2. Isolate Heating Flow and Return
3. Drain boiler via pressure relief valve
4. Check pressure on Expansion Vessel
5. Pump pressure to 0.75 bar if required
6. leave system off for several hours
7. Check pressure has held

I am assuming that if the pressure has dropped then the unit is faulty and I can arrange for a plumber to fit a remote vessel on the return pipework.

Any advice before I go ahead on perform this task over the weekend would be appreciated.

Many Thanks

Hi Scruff,

I have always had a drip on the PRV since the day I moved in about 3 years ago which I assumed was because it had activated and never resealed which I have heard is a common problem.

I've run some tests over the weekend and I have identified two separate leaks on the boiler. One on the Heating Flow near the isolation valve so I am going to order a replacement valve and the other is on the connection to the pump.

I am not sure what to do about the pump leak but I am guessing there is some sort of gasket I can replace without having to replace the pump unit.

Would I be correct in thinking that if water can leak out of the two spots mentioned above then so could pressure from the Expansion Vessel?

I perform the procedure I mentioned in my previous post and I lost 0.4 bar of pressure (with no water in the boiler) in the space of about 10 hours.

I will take your advice into consideration next time and use the dedicated drain valve on the boiler.

With 2bar of water in the system and the F&R isolated I lost 0.75bar of pressure in 3.5 hours.

All tests were performed with the boiler powered down.

Forgot to mention I have never had water come out of the schrader valve when testing / re-inflating.

Cheers Scruff,

I am going to try and get the leaks sorted but it sounds like my expansion vessel is duff too then because after topping up to 0.9 bar it dropped to 0.5 bar in about 10 hours.

I had the boiler drained and switched off all day.

I really appreciate your help.