Its a sealed pressurised system so shouldn't be losing pressure. Leak could be hidden some where. Are there sgns of the safety valve blowing? Either way think you need a heating engineer.
You could still have a leak and it is evaporating before you can see it. Have a look when the heating is turned off and that should show you where it is.
Could also be a 'thingie' inside the boiler itself. Do you have an expansion pipe to the outside? If that is dripping then it could be the seal to that and you will need a heating blokie to sort it.
There is a pressure vessel inside the boiler which can lose pressure. A gas engineer can repressurise.
Whilst you say you don't have a leak, check all radiators carefully. Ours was losing over about a week, turns out when it was fitted the main nut on the towel warmer in the bathroom was slightly loose. Tightened it and it has been fine.
The heat exchanger inside the boiler can corrode through allowing "sealed" central heating water to escape into the hot tap water supply.
I had to get a new boiler, the new ones don't have pilot lights and so use less gas when nothing is running.
My boiler was doing the exact same, losing pressure very quickly.
Traced it to the expansion vessel, tested pressure, it was very low, and used a bicycle pump to re-pressurise to 1 bar.
Been fine since and that's over 3 years now! HERE'S A LINK on how to check the vessel.
------------- I came into this world with nothing and I've still got most of it left.
Hey,
I doubt the Expansion vessel is causing the loss of pressure like your describing.
Take a look outside and see if you have a pipe leading through the wall from the boiler. Is it dripping? If so its your PRSOV leaking. This is the valve that is designed to reduce pressure. A leaking PRSOV is a very common problem on combi boilers due to them sticking open. It's very cheap and easy to fix.
In regards to the last post,if the expansion vessel has lost it's integrity,then system pressure increases as it heats up,causing a loss of water through the pressure relief valve. Then,as the system cools,you will have a lack of pressure. A leaking heat exchanger or diverting valve causes the opposite problem, a rise in pressure will show as a constant drip from the safety. Pumping up the expansion vessel may work,but may only be a temporary fix,and a new one may be needed. An external one may be easier and cheaper,and on bigger systems,work better.
------------- Silence is golden
Duct tape is silver
If you've got a pressure gauge keep an eye on it. Most PRSOV's will let water past at 3 Bar. If when your central heating is running it goes up and beyond 3 Bar then yer its probably your expansion vessel.
Look at it logically before replacing parts willy nilly like most plumbers i have had round. Why go for a more expensive fix first when it could be a 10 quid valve?
I've been through this all before with my 15 year old boiler which now works reliably. And yes i fixed it myself. Every plumber who looked at it was useless. Chastise me if you want (But its falling on deaf ears) but i don't touch gas.
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Topic: Combi boiler question
