My (new) oil combi boiler loses pressure from 1 bar to 0 in about 24 hrs showing I have a weep in the system pipework somewhere. Can't see evidence of leak in surface piping or valves. There is a small section of underfloor piping where I suspect leak might be. Is there a system additive (like rad seal) to stop leak?

Dave Wooden, October 2009

There is a liquid you can buy from a plumbers merchants to put in the water but I would advice you not to put it in a combi system,it is ok for low pressure (tank) systems it could cause damage to your boiler ,better to get someone to repair it.

Glen, October 2009