Wtaer Pressure Loss from Combi boiler

[carlo]

Why does my boiler keep losing pressure over night and the overflow pipe leaks periodically.

I have thermostatic radiators values on all the rads execpt one.

 

[Bahco]

Hi Carlo (bello nome)

Is your filling loop disconnected from the boiler. It could be turned on or letting by.

 

[carlo]

Yes the filling loop is disconnected.

 

[CombiMad]

Sounds like pressure relief valve isn't sealing - either dirt or needs a new one. Try opening it and letting some pressure away to clear muck and then re-pressure.

 

[carlo]

The boiler now when the heating comes on builds up to 2.5bars before the prv lets go and reduces the pressure.
Could this be a faulty expansion vessel?

 

[Bahco]

May need pumping up to correct pressure or replacing.

Not a job for you and you will need to call a Corgi.

 

[gasgeezer]

which boiler is it ?

 

[Agile]

You might get away without a CORGI if you try to pump it up yourself.

Its possible that you could do some damage as well.

Tony

 

[carlo]

The boiler is a Glow worm 24ci. I have re-pressurised the expansion vessel, but the bar pressure still risers very quickly to 2.5bars when either just the water or heating is on.

Could the overheat thermostat be faulty?

 

[Agile]

Yes, but did you reprressurise it with the system OPEN to atmospheric pressure as you were pumping ???

Tony Glazier

 

[carlo]

Yes, but did you reprressurise it with the system OPEN to atmospheric pressure as you were pumping ???

Tony Glazier

Can you please explain what you mean by the system open? Do you mean undoing the automatic air vent on top of the pump?

No I just ensured the expansion vessel was set at 0.5bars.

 

[Agile]

The "system" means the water part, a radiator bleed screw loose for example!

Should be air pressured to 0.9 bar, system closed and water pressure increased to 1.5 Bar.

Tony Glazier

 

[gasgeezer]

interestingly had one 2 months ago the flexible exp, tube was blocked giving same symptons as faulty exp. vess. cleares tube no probs. since

 

[Agile]

You identify that problem by seeing if the air pressure increases from 0.9 Bar to the 1.5 Bar system as the water side is repressurised.

Tony