Why's this overflow always dripping?

[Rom]

Hi

I've got an outside overflow pipe, that constantly drips. To the extent the outside wall is discolouring from mildew or something.
It sits on the back of the house must run under upstairs floor from the height of it. Its the corner closest to the hot water tank, and the cold water tank in the loft(which I think is just for shower)

Info that might help. I have the water tank on constantly, rather than timed. That's on gas boiler, but have immersion tank, for the hot water.

Pics

 

[jeff the gasman]

Check your toilet cisterns and cold water tanks, one of them has a faulty ball valve. You can get the bits for a repair from B&Q
jejj

 

[picasso]

Its either a toilet or have you had a new boiler fairly recently ?

 

[Rom]

Been here a year, only thing done has been a thermostat and a three way valve upstairs.

The toilet is some built in style thing. The flush is on a panel that's also a cupboard under the sink etc. I'll have a look as it must come off obviously.

When you say a faulty ball valve. Is that the float type thing, that should shut water off once tank or cistern is full?

So if I check these, one should be constantly filling? Albeit slowly.

 

[CombustionGuy]

I would say that's your
Toilet overflow and it will need a new float
Valve/ ball valve

 

[longdogs]

I would say that's your
Toilet overflow and it will need a new float
Valve/ ball valve

+1

 

[Armo74]

If you have an isolation valve connected to the cold feed for the toilet turn it off and see if the dripping stops that will tell you if its the toilet float valve.
Or you could run the hot tap and if the dripping stops that would suggest that it's the ball valve in the CWSC feeding the hot water cylinder.