Combi boiler won't fill

Discussion in 'Plumbers' Talk' started by David1098, Aug 24, 2021.

  1. David1098

    David1098 New Member


    I've got a Vaillant Turbomax boiler, there is hot water for a couple of minutes then goes cold. The pressure is at 1 when the boiler is not in use. I've tried to pressurise by opening both valves (as shown in the below link) but water doesn't come in. Any advice would be brilliant

  2. Crowsfoot

    Crowsfoot Screwfix Select

    Very interesting video that d1098.

    The most popular cause of the type of problem that you've got with your h/w is a blocked heat exchanger.
    The not filling issue that's most popular is that one or both of the fill valves are stuck shut and the plastic lever is just moving without the metal valve.
    Try running the hot water tap on at a very slow rate to see if the hot water lasts longer before going cold.
  3. pppmacca43

    pppmacca43 Super Member

    1 bar should be enough.

    Is there a fault code displaying?

    Could be a blockage or an issue with the divertor valve or microswitches. Either way you will most likely need a gas safe engineer to remedy.
  4. David1098

    David1098 New Member

    Thanks for your replies and glad you liked the thrilling video!

    There aren't any plastic valves, just using a screw driver to turn the nuts
    When running the hot water tap on a low level the water still goes cold after a couple of minutes

    There's no fault code

    I think it might be time to call a pro unless you have any suggestions...
  5. Crowsfoot

    Crowsfoot Screwfix Select

    I was testing diverted valve with the slow running tap which seems to be OK. You can't really see what's going on - on a forum.
    Good luck with the diagnosis.

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