Combi Boiler Pressure rises too high

19
Posted 18th Feb
Hi

When my combi Worcester boiler (8 years old) is switched on the pressure from 1.2bar to almost 3 bars!

Online articles suggest it could signal a fault with the pressure relief valve or expansion vessel!

Will ring an engineer after I get back from holiday... Is this an easy fix?

I’ve got free emergency cover, do you think I could use that?
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19 Comments
Make sure the top up tap is fully off, a slight turn can cause excess water to fill the boiler up.
If it’s the expansion vessel then yes easy fix. If it’s covered as an emergency you need to read the T&Cs of your cover. Look at the valve outside your house has it been releasing water? If so it does sound like the vessel is gone
Edited by: "discozohan" 18th Feb
The pressure relief valve is an emergency measure to prevent explosion, they tend to leak causing low pressure rather than high.
Your second guess is much more likely, what you might have to do is release some pressure and inflate the bellows inside the expansion vessel (they usually have a schrader valve, same as cars and bikes)
They don't need a lot of pressure, usually about 12 psi, this video explains how they work youtube.com/wat…cb8
It is possible that the rubber has broken though (water will come out the valve if you push on center pin in valve if it's broken)
SaltyExpert18/02/2020 19:26

Make sure the top up tap is fully off, a slight turn can cause excess …Make sure the top up tap is fully off, a slight turn can cause excess water to fill the boiler up.


Yes already checked that n fully closed.
Depending upon when you are going on holiday and whether you are leaving the boiler on, but I would get it sorted sooner rather than later.
JimboParrot18/02/2020 20:07

Depending upon when you are going on holiday and whether you are leaving …Depending upon when you are going on holiday and whether you are leaving the boiler on, but I would get it sorted sooner rather than later.


Boiler will be turned off n going for 10days tomorrow night.
discozohan18/02/2020 19:29

If it’s the expansion vessel then yes easy fix. If it’s covered as an eme …If it’s the expansion vessel then yes easy fix. If it’s covered as an emergency you need to read the T&Cs of your cover. Look at the valve outside your house has it been releasing water? If so it does sound like the vessel is gone


Which valve are you referring to?
ruheluddin8618/02/2020 20:30

Which valve are you referring to?


Sorry it’s more like a little copper pipe on your outside wall that the pressure relief valve blows out water. It’s going to be where your boiler hangs on the opposite side of the wall outside( does that make sense- it did in my head lol)
My boiler loses pressure and needs topping up every 3-5 days to put it back to 1.2 bar.
But there is 100% no leaks anywhere.
Not sure what it is !
Still working fine , just annoying having to top up .
yozzman123418/02/2020 21:31

My boiler loses pressure and needs topping up every 3-5 days to put it …My boiler loses pressure and needs topping up every 3-5 days to put it back to 1.2 bar.But there is 100% no leaks anywhere. Not sure what it is ! Still working fine , just annoying having to top up .


i can guarantee you that there is 100% leak somewhere. topping up that often means there will be a leak. could be the valves in the radiators are faulty and letting out air or hasn't been shut fully when they were last bled. could also be something inside the boiler leaking.
mutley118/02/2020 21:35

i can guarantee you that there is 100% leak somewhere. topping up that …i can guarantee you that there is 100% leak somewhere. topping up that often means there will be a leak. could be the valves in the radiators are faulty and letting out air or hasn't been shut fully when they were last bled. could also be something inside the boiler leaking.


Definitely not leaking in the house as I would see it in ceilings or on the floor .
Maybe valves letting out air , or inside boiler .
It's a 16 year old cheap Ravenheat heat boiler .
Will be upgrading for next winter .
discozohan18/02/2020 20:38

Sorry it’s more like a little copper pipe on your outside wall that the p …Sorry it’s more like a little copper pipe on your outside wall that the pressure relief valve blows out water. It’s going to be where your boiler hangs on the opposite side of the wall outside( does that make sense- it did in my head lol)


Yes but I think mine is a white condenser pipe? That’s not leaking
ruheluddin8618/02/2020 21:39

Yes but I think mine is a white condenser pipe? That’s not leaking

39935871-A5Mut.jpg
Looks like this
discozohan18/02/2020 22:02

[Image] Looks like this


No I don’t have 1 of those but have a white condensate pipe going into the waste pipe.
39935950-LL885.jpg
ruheluddin8618/02/2020 22:14

No I don’t have 1 of those but have a white condensate pipe going into the …No I don’t have 1 of those but have a white condensate pipe going into the waste pipe. [Image]


Ok not sure then buddy most combi I know of have a copper pipe too for the boiling water to blow out of incase of high pressure.
Most likely expansion vessel, hole in the dhw or faulty filling loop.
But by the sound of it is a faulty expansion vessel. If this is the case you can drain one of the radiators and refill the radiator with water but don't bleed the air from the radiator. The radiator will act as a expansion vessel and would be a temporary cure while you get the problem solved.
yozzman123418/02/2020 21:39

Definitely not leaking in the house as I would see it in ceilings or on …Definitely not leaking in the house as I would see it in ceilings or on the floor .Maybe valves letting out air , or inside boiler .It's a 16 year old cheap Ravenheat heat boiler .Will be upgrading for next winter .

Surely you wouldnt be able to detect a leak from pipework under the floorboards in the kitchen, lounge etc?

Fernox Leak Sealer F4
Edited by: "OllieSt" 19th Feb
OllieSt19/02/2020 04:58

Surely you wouldnt be able to detect a leak from pipework under the …Surely you wouldnt be able to detect a leak from pipework under the floorboards in the kitchen, lounge etc?Fernox Leak Sealer F4


I have solid concrete floors downstairs.
No pipes under floors downstairs.
They all drop down to rads from ceilings .
We had a slow constant leak from a thermostatic valve. The carpet was soaking it up and the heat from the radiator and pipes drying it up so we were unaware of it until we had the combi boiler fitted and pressure kept going!

There could also be a small leak deep/high inside the boiler, again drying up, but enough to cause issues.
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