My toilet flush tank has a problem. Any water that goes into the tank goes straight into the toilet. It doesn't even allow the tank to refill i.e. the water just goes right through and into the bowl. It looks like the images attached. When I press either flush button, something below the red caps moves back and forth (and it sounds normal).

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I don't really know how this mechanism works and what the problem might be. The building handyman says he needs a part that takes weeks to arrive after ordering. Is this a very uncommon design? This is in London, UK.

  • one of the cables must be stuck ... looks like bicycle brake cable .... those two round red things look like they should turn and lift ... if you do try taking it apart, then stuff a towel all around so that small parts do not drop into the tank ... also plug the sink and tub drains in case a spring goes flying across the room
    – jsotola
    May 20, 2020 at 1:37

1 Answer 1


It's a pneumatic valve

https://www.wolseley.co.uk/product/sv93467-pneumatic-dual-flow-valve-15-pc93209-44/ enter image description here

according to this page: https://plumbsparesdirect.com/store/sv93467-dual-flush-valve

If the flush valve is letting by water into the pan the most likely problem is that the flush valve washer has failed To replace the Ideal Standard flush seal and clip turn off the water and empty the cistern then simply twist the body of the flush valve from the cradle, pull off the worn washer push on the new one twist the body back into the cradle and then refill the cistern Please refer to attached diagram for further fitting instructions

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