my hot water boiler is losing pressure my boiler is a valiant?
I suspect you have a leak somewhere but have a look at the following website www.diyenergysavings .uk
? I have to top up the water pressure in my combination boiler every year or so through a valve under the boiler.. when it drops too low the boiler just stops working... I don't know if your talking about the same thing but its probably the most common fault and a very easy one to resolve ... if your not sure how much pressure to put in it? fill the system to 1.2... There should be a topping up loop off the cold water supply to top up the pressure. I have never seen a combination boiler on the UK with a separate expansion vessel.. Only time I see external expansion vessel's is on cheaper water heaters to allow expansion after a one way valve ? but I'm not a plumber..
this could be due to a leak? if your expansion vessel as lost pressure your pressure gauge will rise up to 3bar of pressure when heating is on then go down to 0bar when it turns of you don't always have to change the vessel it can be re pressurised using a foot pump with a gauge on and pumping back up to 1.5 bar experienced plumber
Yes, this happens after a time, you need to either replace the onboard expansion vessel (very expensive), or fit an external expansion vessel. The external one is better because you don't disturb anything and you are adding value to the current capabilities of the existing one. To decide what size you need to know the capacity of the system in litres, and then use the manual to determine correct size.
The most common reason a boiler (hot water or steam) will lose pressure is; WATER. You are either losing water some where or where low to begin with. If your losing water as your putting it in then you have a leak. Try adding some and see. Good Luck
