Constant hiss type sound coming from beneath toilet

[Andrew76]

Hi, we're having an issue with our toilet in which only for the past few weeks a slight hissing sound happens 24/7. It sounds something is running through the pipes although there's no clear signs in the cistern or with the water meter etc. It isn't that loud, but certainly noticeable with no ambient sound. Every so often the sound will get a lot lot louder and then stop within a minute or two.

No signs of a leak or anything like this. The extra loud sound just happened and I felt the pipes, there did seem to be a slight vibration through the 'main' water pipe (which has the stopcock on). I can't be 100% sure as it stopped as I was checking.

Any help would be greatly appreciated. Many thanks.

 

[Chuck]

A very small leak resulting in an extremely fine jet of water can create a surprisingly audible hissing sound. If this leak, e.g. across a valve seat, occurs inside a tap or float valve you may only see a couple of drips a minute from the outlet.

If it gets louder when you lift the lift off the cistern your float valve needs servicing or replacing.

 

[PETE 123]

Turn water supply off and see if it stops.