System losing pressure

[duzu]

My central heating system is based on a Worcester Greenstar system boiler. The system has been losing pressure slowly for the past year or so, needing a top up through the filling valve every fortnight or so. In the past week, the pressure loss has become much more severe, with the pressure dropping from 1.5 bar to the lowest point on the gauge (red zone) in about 2 to 3 hours.

There doesn't appear to be any leaks around radiators or in the garage where the boiler is located. I guess the leak would be quite obvious since I am topping it up quite regularly now.

I checked almost all radiators for air and there were two that needed bleeding but nothing unusual and the situation still persists after bleeding.

I am also noticing that the radiators are not outputting the same heat. A couple are almost too hot to touch, others luke warm and others almost cold. Also one or two radiators are making a gurgling sound occassionally. These have all been checked for trapped air. I understand the difference in temperature means that the system needs balancing, but not sure if this is a separate problem from the pressure drop or a related one.

Any ideas what the issue could be? Could it be the built-in pump that is faulty and not developing enough pressure for the circulation? Could it be a defective expansion vessel?

Thanks.

 

[cross thread]

Does the pressure hold if the heat and hw are off.

 

[terryplumb]

You have a leak. Either emitting from the boiler or the central heating pipework/ rads/ valves.
Is water dripping from the copper pipe outside ( pressure relief pipework ) ?

 

[duzu]

@cross thread : I tried that and it's gone down from 1.5 bar to about 0.7 bar in 40 minutes with the boiler turned off.

@terryplumb : Yes! There is a pipe from the boiler terminating just short of the front garage door and it seems to be dripping. I never noticed as the pipe terminates behind some timber boards. Is this a pressure relief system in the boiler? Is it faulty and stuck open? There is also another copper pipe from the boiler that seems to be going into a 6" drain coming from the upper floor.

 

[terryplumb]

The boiler has a pressure relief valve inside it ,copper pipe runs from boiler to outside and is open ended and not connected to a drain. If water is coming from it ,your system pressure will drop. It should only let water out if the pressure in boiler / sealed central heating system approaches 3 bar.

 

[sxturbo]

Your expansion vessel might have failed , this would cause the pressure being to high.

This could cause the relief valve to open and now it's stuck.

Not sure if you be able to get an engineer out at the moment.

 

[duzu]

Thanks for your help. I'll try to find an engineer to check it out.