Pressure drops over a week in gauge connected to red expansion vessel from 0.8 to 0.7 bar

[Question]

A plumber has recently installed an unvented system, replacing a gravity system.  I noticed the pressure has dropped from 0.8 to 0.7 bar over a week (gauge over red expansion vessel), and I think it is still dropping  The pressure figures were recorded at the same time of day (6.15pm) as I wanted to exclude the effect of the boiler being on or off.

 

I have spoken to the plumber who is still working on our site.  He said that it could be very small leak and that he would have a look.  He seemed somewhat unconcerned.  I am disappointed that the plumber was not monitoring the pressure level himself.  I imagine finding a very small leak to be very difficult.    If this does not get resolved, I would presumably need to re-pressurise the system every two to three weeks. 

 

I am worried.  Do you have any advice please.  

[Chanmenie]

I had same problem but could not find a water leak anywhere, turned out to be the shrader valve on the expansion vessel, so a £1:50 fix 

[Question]

Thanks for your reply.  How did you find out it was the shrader valve when it could have been so many other things? 

[Chanmenie]

6 minutes ago, Question said:

Thanks for your reply.  How did you find out it was the shrader valve when it could have been so many other things? 

Because I could not find a water leak so deduced it could only be air and the only place air could leak out is the expansion vessel 

[Temp]

Go around every rad yourself. Have a good feel all around the pipes and valves checking for any dampness. It's easy for small leaks at rads to run down the pipe and dissappear. 

[Question]

Thanks for the information.  One other thought is to put some liquid around the shrader valve and see if it bubbles.  That is what they do with car tyre leaks so perhaps it will work a shrader valve.  I'll see what the plumber does first. 

[Bonner]

I had a similar problem. Couldn’t find a leak anywhere but pressure dropped 0.5 bar over 2 weeks. A dose of Leak sealer solved the problem 

[Chanmenie]

3 minutes ago, Question said:

Thanks for the information.  One other thought is to put some liquid around the shrader valve and see if it bubbles.  That is what they do with car tyre leaks so perhaps it will work a shrader valve.  I'll see what the plumber does first. 

Yes I did that, weak solution of water and soap works best, use the same for finding punctures in tyres 

[Question]

Can I exclude the radiators as a source of the problem, as they are not heating up at all?  It is summer and it does not get cold enough.  so the radiators are off. 

Edited July 5, 2022 by Question

[Chanmenie]

43 minutes ago, Question said:

Can I exclude the radiators as a source of the problem, as they are not heating up at all?  It is summer and it does not get cold enough.  so the radiators are off. 

No you still need to check for leaks 

[dpmiller]

has the ambient temperature changed? Was the first measurement taken on a sunny day? Pressure will fluctuate with temperature regardless of heat source

[ProDave]

New installation could still be air bleeding out of an automatic bleed valve?  0.8bar is a bit low, try re pressurising to 1 bar and see how it goes.

[PeterW]

As above - should be running in the 1.5-2bar range when hot, so around 1.2bar cold. I would push up to 2 bar into the system and then check. I would also check the setting on the expansion vessel as sometimes these are set low and the bladder may be under pressure. If it’s a new system then you may have air in the system in high points - did he add inhibitor too ..?

[Nickfromwales]

If the rads are off, +1 to it very likely being air still in the system being vented at the automatic air vent in the boiler. If the boiler does a pump overrun cycle after hot water has been satisfied, the pump will circulate the heating circuit water to cool the boiler heat exchanger down ( but this is manufacturer dependant ) and should be ruled out first. 
I would run the central heating flat out at full temp with all radiator valves set to max temp and do that for a full 1 hour. That will purge all the air from the heating circuit and only then can you really start the next processes of elimination. 
Yes it’ll be very warm, so time it gif an hour and go out for a while to allow the house to cool back down. 
Start there. 

Edited July 5, 2022 by Nickfromwales
Big thumbs

[Question]

GOOD NEWS !

 

The plumber found a leak.  It was on a new radiator installed by a previous plumber and the floorboards were not yet fixed in place.  The leak was in the pipes under the floor and he was able to repair it.   

 

Hopefully that will resolve it, but I thought the plumber should be monitoring the pressure gauge, not me.   My expectations are quite low with tradesman, and I feel sometimes that I am doing their work.  They always want to cut corners.  

[Question]

Thanks for all your advice and comments which is really appreciated.