Boiler losing pressure - at a loose end

Discussion in 'Plumbers' Talk' started by MountainMan, Nov 30, 2021.

  1. MountainMan

    MountainMan New Member

    Our house was built in the mid 70s. Copper pipe laid in the floor and not lined, in some areas very close to the surface. Many houses on the street have rerouted their central heating piping and some have had leaks. We had a Worcester Combi boiler fitted around 3 years ago.

    A couple of months ago there was a leak in our hallway floor, under parquet floor. The area of the leak was obvious and whilst it damaged one floor, we were able to claim against it with home insurance.

    Even though this leak has been fixed (piping was visible and dry for a long time) our boiler pressure continues to drop at a rate of around half a bar per 2 hours.

    A builder and plumber whilst assisting with the leak also witnessed the pressure dropping completely and rapidly when the hot water was tap was run. I saw this as well but it has not happened since.

    At the time, a Worcester employee suggested it might be the heat exchanger plate however we had a Worcester engineer out who isolated the boiler and tested to see if the pressure would drop. It held for over 4 hours and dropped when he released. His conclusion was that there was a leak in the piping somewhere.

    There is no visible water in any of the rooms or under the floors.

    We know will have to reroute the piping after Christmas (although easier said than done getting hold of people at the moment) however want to minimise the amount of damage caused if there is a leak. And be able to prove the issue with the boiler if that is what's at fault. We have very young children so the prospect of going without heating is not a good one but we could probably manage with electric heaters downstairs if the underfloor heating got shut off. Also cost and disruption to the whole house is a factor in dealing with this.

    Long post I know (thank you if you're still here). My questions are:

    Given the rate of the drop in pressure and the amount of time this has been going on, would it not be a sure thing that the water would have shown? The first leak was clear as day and the pipes are so close to the surface.

    Could anything else cause the pressure drop?

    Any suggestions in finding locating the leak? (I have purchased a Flir One Camera which hasn't really helped but has highlighted damp patches in one wall).

    Any other thoughts about the boiler or suggestions moving forward also welcome!
  2. Jimbo

    Jimbo Screwfix Select

    You need a gas tracing specialist. Basically they drain the system and feed it a gas then use a gas detector to find the leak. Since the gas can seep through the floor it can be detected even if the water is just draining away.

    You don't want to hear this, but... in my experience the entire downstairs pipe work will need replacing one way or other. Once there is a leak many more will follow.

    Random leak: Water Pipe Leak Detection - Gas Tracing - Pinpoint (
  3. MountainMan

    MountainMan New Member

    • Thanks Jimbo, we are preparing ourselves to shut off the downstairs pipework and reroute above the surface. Just seems like plumbers we've contacted are very busy/unable to do the job right now so haven't even had a quote for it yet.
  4. Jimbo

    Jimbo Screwfix Select

    If you can isolate the downstairs as a whole that should sort it, try and leave some drain valves somewhere though. Then use other heating for now downstairs.
  5. Notnowvicar

    Notnowvicar Active Member

    ..have you checked the expansion vessel holds pressure ?
  6. MountainMan

    MountainMan New Member

    I haven't, I wouldn't know how. I'm not sure if the plumber or the WB engineer that came out did this either to be honest. Think its worth getting someone back to do this?
  7. terrymac

    terrymac Screwfix Select

    No. The engineer isolated the boiler ,and pressure didn't drop . Rules out the EV. When boilers isolation valves were then opened ,the pressure dropped immediately ,you have a leak on the system side.
    MountainMan and jimbobby like this.

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