Boiler losing pressure

[impreza280]

Hi - I'm trying to diagnose why my Baxi Barcelona condenser boiler is losing pressure. It's connected to a megaflo and underfloor heating. I've turned off the flow and return on the underfloor heating and the problem is still there, so I assume that takes away any possibility of a leak within that? And there are no signs of any leaks around the boiler or between it and the megaflo.

It's gradually getting worse rather than a sudden problem and can be temporarily cured by topping up via the filling loop , or re-pressurising the expansion vessel (a bit of water came out when I released the last bit of pressure).

What are the possible issues and what could be done to prove what the issue is?

 

[picasso]

Isolate the boiler overnight and see if the pressure drops, also look outside and you will find a 15mm copper pipe connected to the boiler, tie a balloon over the end and see if any water collects in it.

 

[impreza280]

Isolate the boiler overnight and see if the pressure drops, also look outside and you will find a 15mm copper pipe connected to the boiler, tie a balloon over the end and see if any water collects in it.

I think I've found the problem before I've even isolated the boiler or used the balloon - I've re-pressurised the expansion vessel and I can hear it leaking from the valve.
If I get a schrader valve extension, is that likely to fix it?

 

[terryplumb]

Needs sorting for sure . Does your boilers pressure gauge reach 3 bar when your central heating has been running for an hour or more ?

 

[impreza280]

Needs sorting for sure . Does your boilers pressure gauge reach 3 bar when your central heating has been running for an hour or more ?

If I pressurise the boiler to 1.5 bar and do likewise with the filling loop, the most it reaches when the heating is on is 2 bar.

With the boiler off, I re-pressurised to 2 bar just now and it's down to 1.5 bar within 15 mins, hence I'm convinced the leaking valve on the expansion vessel is the cause.

 

[dal5band]

Try the bubble test on the valve - soap bubbles will show up the leak. As a test, you could put a cap on it to see if that fixes it or slows it down.
You can change the insert on the shraeder valve if its the same as a car valve - have to de-pressurise the system.
Get some valve inserts from Halfords together with an extraction tool , its a little prong thing. You probably got one in your bike kit.

 

[impreza280]

Try the bubble test on the valve - soap bubbles will show up the leak. As a test, you could put a cap on it to see if that fixes it or slows it down.
You can change the insert on the shraeder valve if its the same as a car valve - have to de-pressurise the system.
Get some valve inserts from Halfords together with an extraction tool , its a little prong thing. You probably got one in your bike kit.

New valve inserted, re-pressurised to about 1.4bar and it's now holding pressure. There's about a teaspoon of water in the balloon on the external pipe after a couple of hours, so it sounds like I've fixed the bigger problem but a minor problem may still exist, but if it becomes significant then that looks like a straightforward replacement PRV fitted by a GasSafe engineer.

Thank you for all advice - this thread plus watching a couple of youtube videos has helped out massively.

 

[impreza280]

24 hours on and the pressure is still OK, but has dropped from 1.4 to 1.3. The balloon I put on the exterior pipe has a small amount of water in it after 24 hours - I guess 50ml. Does this suggest that the PRV is not totally shut and needs 'a clean' or replacing?

 

[terryplumb]

Yes ,if it's passing water it needs examining ,possibly replacing.