New en-suite installed last year, the push button cistern is hissing almost constantly, when you lift the lid and look down into cistern there is the main part and to the left a smaller part , the hissing seems to originate from the top bit above the water level, apologies for poor description but DIY is an alien concept to me
Since you describe a hissing noise, that sounds like it coming from the mains pressure side. I think the problem is that the inlet valve is not closing fully. Doesn't sound like an outlet valve problem.
I just fixed mine, there was a small bit of grit under the inlet valve. See another question and answer on this website for some great instructions on how to dismantle it.
Richard (Surrey)
October 2007
It's probably the valve at the bottom leaking and letting water drain away. The cistern is then trying to fill back up all the time. I have smae problem with a dual flush cistern fitted 2 years ago. Only way to fix it is to replace part i think.
Ralph
October 2007
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