Combi boiler loss of pressure

[Ronco71]

Hi, I wonder if anyone could help me with a problem that's been driving me mad?

I moved into a house around 1 year ago with an Alpha Combi boiler & I've been experiencing pressure drops of around 0.25 bar per day while the central heating system is working. The boiler is fully serviced and has been checked for pressurization and water leaks and has been given a clean bill of health. The pressure release value is also working satisfactorily. Despite this I still have to top up the system every 1 to 2 days.

During the summer months, when the central heating system does not kick-in and I'm only using hot water, the pressure is maintained. It is only when the radiators are used that the pressure loss occurs. With this in mind I have found that by turning off all the upstairs radiators I can maintain pressure while the downstairs is heating.

The radiators themselves must be at least 20 years old. I have found no evidence of any leaks around the house. If the valves or radiators were leaking then surely there would be some evidence ?

 

[Agile]

A small leak on a hot rad will evaporate.

I suggest you very carefully feel around all the valves when the system has been for several hours and see if you hand shows any evidence of water.

If not the pull off all the valve caps and you will probably see the shaft seal is wet on at least one.

Tony

 

[Ronco71]

Thanks Tony, I'll have a closer look. Do these symptoms suggest that it is likely to be a valve/radiator leak ? We could not comtemplate lifting flooring, especially downstairs.

Graham