Combi Boiler loosing pressure

[ort67]

Hi,

I have a Vokera combi boiler in a flat with about 7 radiators, but it is loosing pressure if anyone can advise me on the best course of action.

This morning I topped it up to 1 bar but now 12 hours later it is at
0.6 bar.

My down stairs neighbours haven't complained about any leaks, I'm not sure if the pressure relief valve is faulty and letting water out, I can see the outlet outside but can't get a good look at it because I'm on the 4th floor, but I haven't visually seen any water drain from it.

I've lived in the flat for a few years and it has always needed topping up now and again, about a year ago I put some of the below Sentinel leak sealer in it:

https://www.screwfix.com/p/sentinel-internal-leak-sealer-1ltr/99730

This seemed to make it settle down a bit, but in the last couple of weeks it's started dropping quite quickly.

I've bought some of the below to put into it:

https://www.screwfix.com/p/fernox-f4-central-heating-leak-sealer-500ml/45902

I'm really hoping that putting the fernox into it will stop the pressure dropping, but I've read some places that leak sealing liquids can damage a combi boiler?

Might the fernox react badly with the sentinel that I put in previously?

I'm not sure what other alternatives are, I'm praying it doesn't come to tearing up floorboards to find a leaking pipe.

In the past the pressure drops seem to be kind of random, for a few weeks it will be ok then all of a sudden it will gradually drop down a bit.

 

[terryplumb]

When you top pressure upto 1 bar ,when system is cold ,and then run your c/heating for a few hours ,what does the pressure increase to ??

 

[ort67]

When you top pressure upto 1 bar ,when system is cold ,and then run your c/heating for a few hours ,what does the pressure increase to ??

I can't remember exactly but I think it is usually somewhere between 1-1.5 maybe 1.2 or 1.3 bar.

This morning I turned off the boiler and filled it up cold to 1 bar then it dropped to 0.6 bar, it's been steady on that for the last couple of hours.

 

[terryplumb]

OK ,you may be losing pressure within the boiler ,or on the system pipework /radiators etc. If you want to establish which ,you can set pressure to 1.5 bar ,when cold.then close the isolation valves on the boiler and electrically isolate it. You would then have to leave it for ideally 24 hours ,if you can survive without it that long. If you then check the pressure ,and it has dropped ,its losing within the boiler. If it has not dropped ,open the isolation valves .if it then drops you know its losing pressure on the system.and can the decide what steps to take to resolve.

 

[ort67]

OK ,you may be losing pressure within the boiler ,or on the system pipework /radiators etc. If you want to establish which ,you can set pressure to 1.5 bar ,when cold.then close the isolation valves on the boiler and electrically isolate it. You would then have to leave it for ideally 24 hours ,if you can survive without it that long. If you then check the pressure ,and it has dropped ,its losing within the boiler. If it has not dropped ,open the isolation valves .if it then drops you know its losing pressure on the system.and can the decide what steps to take to resolve.

Nice thanks for the advice.

It's a Vokera Excell 80sp I have, in the manual there are the Central heating flow valve and Central heating return valves, is it just these the two I should close when it's up at 1.5 bar when cold and isolated?

 

[terryplumb]

Yes flow and return valves

 

[ort67]

Yes flow and return valves

Thanks, that's it topped up to 1.5 bar and the valves shut, we'll see what happens now.

 

[terryplumb]

Time will tell !!!!

 

[ort67]

Time will tell !!!!

I checked it this morning and it has dropped to 1 bar with the isolation valves closed, so that must mean its being lost internally?

What do you think the next step would be, get a plumber in?

 

[terryplumb]

That's encouraging . Think you now need an engineer to establish ,and you can explain what you have done .also when you open the valves to c/heating ,see if it drops further. The prv in the boiler would be my first port of call

 

[ort67]

That's encouraging . Think you now need an engineer to establish ,and you can explain what you have done .also when you open the valves to c/heating ,see if it drops further. The prv in the boiler would be my first port of call

When I opened the valves I didn't notice a change in pressure, does that still indicate it's being lost within the boiler?

 

[terryplumb]

Yes, if pressure had dropped when valves closed the loss is within the boiler.

 

[WhatNext]

Hi I have a similar issue. I note that there are 2 vertical marks at the top and bottom of the isolation valves under my Vokera Excell 80SP boiler. Is it just a matter of backing off the phillips screw and turning the valve head through 90 degrees to close it ?

I have heard that these isolation valves are notorious for leaking once disturbed - is this true ?

 

[terryplumb]

You should start our own thread ,whatnext ,or the mods won't be happy with you for " hijacking" this one mate. Any way ,to isolate flow and return at boiler ,just 1/4 turn till notches are horizontal. And yes sometimes isolation valves can leak. No screws to loosen either

 

[endecotp]

I'm not sure if the pressure relief valve is faulty and letting water out, I can see the outlet outside but can't get a good look at it because I'm on the 4th floor, but I haven't visually seen any water drain from it.

You might consider disconnecting the PRV pipe at the boiler end so that you can see if anything comes out without having to climb the wall.
Of course there is a potential danger here as you don't want boiling water spraying around, but since you're seeing the pressure drop even when it's cold you should be OK.