Heating system gradual pressure increase over days..

[Ponx]

hi there. My heating system is gradually increasing in pressure measured when the system has not been running for say 8 hours. I measure this at the same time ie 5 pm each day when the system is cold. Over a ten day period the pressure has gone from 1.5 bars to 1.7 bars. It’s not the filling loop as I have disconnected it . It’s not a combi boiler, so the only other thing I can think of is there is leak from the hot water cylinder coil. The cylinder is a 300l Ariston one now 12 years old. Any other suggestions please ??

 

[Scott_D]

Isolate the cold water to the cylinder
Depressurise at a tap
See if it goes up

 

[Ponx]

I get the idea, but would have to have the hot water off for a few days to see if it made any differences it increases only slowly ie o.2 bars over ten days...

 

[Stigster]

Try it over night and see if you can see a difference on the gauge. Might just be long enough to show it. Set the pressure dead on 1 or 1.5 and check it again in the morning.

 

[Burger]

What boiler is feeding it?

 

[Ponx]

Worcester Bosch Danesmoor oil fired boiler.

 

[Burger]

Worcester Bosch Danesmoor oil fired boiler.

My apologies, I don’t know enough about oil boilers, however plenty on here do. I was just trying to establish if it was a vaillant with a water pressure sensor.

Could be the coil does have a pinhole.

 

[Scott_D]

Is it constantly rising?
Eg if you left it a month it would hit 3

 

[Ponx]

Not sure. Haven’t tried to leave it that long as would be concerned that the pressure would build to be too high... what I have tried is to bring system pressure to zero, re-pressure the expansion vessel which was low and then pressured the system back again. After this in ten days it went from 1.53 to 1.7 bars exact same time of day.

 

[Stigster]

If it was my system I would let the pressure continue to rise, assuming everything else is as it should be as the pressure relief valve will kick in long before any harm can be done.

 

[Ponx]

Okay, thanks...