Baxi 105 rapid pressure loss

2 Mar 2013
Reaction score
United Kingdom
Checked all radiators no leaks above the floor and nothing through ceiling into lower ground floor, listened as able at all radiators no water leaking sounds. Have isolated the boiler by closing pipes to and from central heating and turned boiler off and pressure still dropped from 2 to 0 over afternoon.. On turning on valves for central heating supply and return little rise in pressure , with boiler switched off still . I left boiler isolated with pressure at 2 for above 6 hours. If pressure decreased with central heating supply isolated is the boiler at fault? Also shhouldnt there be an increase in pressure once the central heating supply in and out are turned on again? There was a lot of air in system should I repeat with all radiators full of water? Also no water out pipe into garden, not even a drip!! Reluctant to pull up oak wooden floorings e want to exclude everything first. Could there be a leak in heat exchanger. Would you always see water dripping, also pressure seems to fall when using hot tap and fails to rise to level before tap was run. Had a few engineers our, one thought expansion vessel, put some air in left other thought leak under advice appreciated
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If its a he model

Sounds like the recuperator is shot, that's if you have confirmed the prv isn't passing and there no components leaking around the boiler.
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