DIY Doctor UK DIY Forums

Hi,

Hope someone can help. Have a two year old Worcester Bosch boiler that is losing pressure.

Had WB come out and replace PRV under warranty but still got pressure drop.

However, outside there are TWO overflows from the boiler....one copper pipe from the PRV and one white plastic from somewhere else within the boiler. When the system is cold / not under pressure (heating and water off) and pressure is topped up to around 1.5 bar, the pressure drops slowly to zero over around a three hour period, with no visible water from the overflow outside. However if I then turn the heating and water on, after around 10 to 15 minutes, water can be seen gushing out of PLASTIC overflow and then stops. Then again after around 10 to 15 minutes it happens again. Anyone any idea what this problem is ? Faulty / split expansion tank ? Faulty / split heat exchanger ?



Thanks in advance

The plastic pipe is the condense pipe and discharge is normal, it should terminate to a drain. The pressure loss is either a leak on the system or the expansion vessel has lost its pressure. Call Worcester to check it

Thanks. Update is that if I raise the pressure to 1 bar when cold and put CH on, the pressure will raise to around 1.5 bar and hold until CH switched off. The pressure then drops to around 0.25 bar when cold. However the pressure doesn’t drop any further (ie zero). When CH is then switched on again the pressure goes to around 1 bar and holds constant and drops to around 0.25 bar when CH is switched off and cold. So it appears that I have a leak which only opens up at pressure above 1 bar. I’ve got a leak detection company coming to do a thermal map / smoke detection to find the problem. Costing me over £400 plus cost of any remedial work but better safe than sorry !!