boiler loses pressure and water leak..

23 May 2015
Reaction score
West Midlands
United Kingdom

Boiler (about 1yo, replacement of a backboiler) lost pressure (zero) few days ago, (zero day)
I checked around the pipes of the rads and even the overflow pipe no sign of water leak.

I re-pressurised it and all ok for one day. Then next day (day-1): water leak on the kitchen's floor (concrete). I left the boiler on (no CH, just for Hot water), day-2 we mopped the kitchen
floor from time to time, then during evening the boiler's pressure went to zero again, at that
point I turned off the boiler. Now the weird thing: next days: "day-3" and "day-4"
no leak from the kitchen floor...

First thought was the water pipe (under kitchen's floor) (unfortunately is being shared with a very problematic neighbour, I did not try to isolate the main (on the road) valve)

I know the darn pipe under the kitchen's floor is lead (1930's house) but how could that
possible -its under concrete anyway- and why that happened when the boiler was filled (pressurised). my plumber is a bit busy those days, just I am scratching my head trying to understand this.
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The lead water pipe will not be part of your sealed central heating system. Are any central heating pipes in the concrete floor ,that's most likely ?
Thanks Terry, I got it... this is the explanation then.
I don't know if there are any CH pipes under the concrete -no records about past maintenance
and mind: ex-council house...
But I bet you are 100% right:
There is only one radiator in the kitchen but btw originally the kitchen was two separate rooms, then sometime a previous owner knocked down the middle wall, so they probably capped off the underfloor pipe then installed new tiles.


water comes from kitchen ceiling, I did not even noticed as cupboards over the leaking spot, the water came from the ceiling then followed the path via the wall..

anyway, upstairs floor is squeaky -and we did not pay any attention so many years- what we found: there was a screw that came with contact with CW pipes underfloor, so that sh*t slowly managed to cause damage to the pipe... at least is
not something pipe under the concrete.
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