Toilet cistern losing water

[Kieran]

Hi all, just need help with a head scratcher. Got a call to a close coupled cistern losing water, every hour or so the ballvalve drops to refill it. Theres no leak visible (this has been going on for a year) and no water is passing by the siphon into the pan. I dried the pan and left toilet roll around the inside of it which was still dry the next day. I can actually hear water dripping which must be straight from the cistern into the waste. Any thoughts? Going to change the siphon anyway, just dont understand how the water is going straight to the waste instead of the pan. Thanks in advance

 

[stani]

Is it a syphonic close coupled?

 

[Kieran]

Nope, push button dump valve type

 

[Best]

That must mean there are two faults, -
(1) There is water either passing through the flush valve, or passing out the bottom of cistern where the flush valve tightens on.
(2) You also have something wrong inside the pan that allows water to drip straight into the soil pipe.

I would firstly check the flush valve is properly sealed to the cistern base. Some cisterns are misshapen. Perhaps also replace the valve, as you say.
Just a thought, - wonder is it an old type syphonic toilet and someone has previously replaced the old syphon and Airex with a modern flush valve? That would mean a small hole left open in pan below the cistern. Toilet would never flush properly though if Airex removed

 

[Kieran]

No its a new toilet, only a few years old. It has a normal dump type push button siphon. I checked around the pan and dont see anythin abnormal about it, water just empties straight into the pan. I agree there must be something wrong with the pan itself, just cant see where the round siphone hole can connect to the waste, they arent connected at all, apart from the bowl itself. Strange one

 

[Best]

Maybe a fault in the pan letting water into sewer and even if you fixed the leak from the cistern there could be risk of sewer gases directly coming into cistern

 

[Old Account]

Perhaps you've got some pictures for us

 

[Ch4 plumbing]

If your 100% sure that it isnt going into the pan then have you checked the cistern for a crack at the back and the water running down the wall?

Long shot lol

 

[Old Account]

I don't believe the water will drop straight into the waste it's not possible. You could put pepper into the bowel on all sites so then will see if there is any slight / minor leak into the bowel. Or as mentioned above did you inspect the cisternif there is any crack most of the time you won't see it if that's very minor.

 

[king of pipes]

Few drops of food colouring in the cistern will pick up any leakage and flush away