Ideal Response Boiler losing Pressure

6 Dec 2008
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United Kingdom
afternoon all. hoping someone can assist.

Here are the details of the boilder:

Ideal Response 120 - serviced about a year ago
Location: Kitchen - safety expansion outside
house: 2 floors and loft


Boiler is losing pressure when central heating is on. I will come in and pressure has dropped to zero. If i fill up to say 1 bar - and put the heating on - pressure will rise to over 3 bar and a puddle of water can be found at the base of the boiler unit. I've just checked the overflow valve outside and this is dripping a fair bit of water whilst the boiler is on.

What I've already checked:

Have looked for obvious leaks - nothing can be found, have floorboards and carpet and therefore can only really look around radiators etc. Checked and bled radiators. no obvious problems.


The pressure on the boiler keeps if I don't turn on the central heating - i.e just using hot water for showers and hot taps etc. its only when I switch the central heating on that the pressure then drops.

Please help!

Many thanks
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expansion vessel needs recharging, see FAQ
also PRV is probably duff now, these are a bit of a pig to change on these if I remember rightly.
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If you are lucky the EXV can be recharged but it might have failed !

Often the PRV can be "clicked" about six times and it will often reseal after a few days. They are a pig to change !

like micky g said you have a faulty expansion vessel u could try re charging it or maybe it has finally perrished
get yaself a foot pump with a pressure dial on it. then at the back off the boiler you will find a ex vessel might be inside the casing dont know this boiler to be honest. then what u need to do it undo the the dust cap n press the pin like u would let a tyre down n see if water come out if it does no point as u will require a new one. if not then inside the casing you will see a red handle with 3 bar on it. u need to twist it and keep it open u will know what i mean when you turn it. whilst its open attached the pump n pump in 1 bar of pressure then take the pump off the adaptor. n check that u have pressure in there. then close the prv and re prssuise your system bleed n test see how u get on with that
thanks all for the response - sounds a bit out of my league to be honest - I'm a true DIY not. will have to call a plumber or would you say an engineer would be better?

finally - is there any danger in continuing to fill up and warm the house occasionally while i wait to get someone in?
you will be ok to do that as a temporary measure yes, but long term it will do damage, by encouraging corossion.
the vessel has gone mate, the vessels on the response like most of the response were crap, you can call ideal and they will come out on a one off call out charge of about 200quid and change it, and the pressure relief valve, plus whatever is needed. i used to work for them as an engineer now i work for worcester bosch. the response always was and always will be a poor boiler. if money is available change the bloody thing for something better like a greenstar or vailiant ecotec. good luck.
We had a similar problem with our Response 100 last year. The system was regularly reading 0bar, we were topping it up and it was leaking outside. As it got worse and the heating was reading 3.2bar the pipes in the house started to creak with pressure, so I'd get it sorted. Our engineer said from the start it had an air leak in it, but called five times on his way home to assess problem or pump vessel back up in the hope he was wrong and could save us money. A new vessel set us back about £100 but our engineer only charged us £15 for fitting it and previous visits!

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