Header tank overflow problem

[theoldboy]

Hi everyone.

I've a problem with an 'dripping' from the header tank overflow, which seems to occur early in the morning, presumably because no demand has been made on the tank.
Further info. Excuse me if my terminology is not correct.
I don't believe it's the ball cock valve, I've changed this and I can't see any dripping.
I can see what seems to be 'percolation' coming in from the pipe that leads to the hotwater tank - I can see a flow pattern.
I don't think it's a problem with the coil in the hotwater tank itself, as my boiler is relatively new and there's a mechanism for monitoring water pressure - I can put more water in if i lose it and it doesnt move enough to justify loss anywere.
It looks as if the hotwater is fed by the hotwater tank but the cold is fed to all taps by the mains.
There's only a tank in the roof.
I've used the mains-in tap to reduce the pressure so that full on hot flow seems the same as full on cold flow, if that makes sense.
But I'm still getting overflow.

Any thoughts/other stuff I could look at. I'm loathe to change anything without being certain it will cure the problem. ie some logic to the cause and not a 'might be'.

It has been suggested that I may have a mixer tap that is letting water through - cold to hot. is there a "thickery's" way of proving of proving this?

Cheers

what header tank ?
the small f/e tank or large cws tank ?
what boiler do you have ?

[theoldboy]

I only have a large cold tank that feeds the hot water, The 'heating' is closed? ie no take, but a gauge and tap - Vailant 'condensing'? boiler.

sealed heating system, gravity hot water.
as you have mentioned you have a mixer tap or shower mixer that is gravity hot mains cold that is getting back flow from cold mains to hot gravity.
you need to isolate each mixer tap etc to locate what one is at fault. then when located the faulty mixer install a check valve to the hot supply near to the faulty mixer to prevent happening again.

as for turning down your mains to the same flow as the hot water only reduces flow not pressure.
the only way to reduce pressure is a pressure reducing valve.

[theoldboy]

Originally Posted by ajs heating

you need to isolate each mixer tap etc to locate what one is at fault. then when located the faulty mixer install a check valve to the hot supply near to the faulty mixer to prevent happening again.

Interesting approach - I'd have expected to reduce pressure before the tap perhaps, didn't think about the check valve (didn't know there was such a thing! )

Originally Posted by ajs heating

as for turning down your mains to the same flow as the hot water only reduces flow not pressure.
the only way to reduce pressure is a pressure reducing valve.

Must admit a problem in my logic was tickling the back of my mind - I'm sure I may have come across this issue of flow/presssure before.

I'm very grateful for you feedback - I'll review my options on check valves - it may be simpler/cheaper/quicker to gravity feed the cold too perhaps

Cheers

that is one way round it yes. cold from the tank.
it is a water regulation that cold mains hot gravity mixer taps must be fitted with a check valve. but check valves can sometimes restrict gravity hot flow to much as they have a spring valve in them.

[theoldboy]

Cheers
I'll review - thinking further I may simply fit a pressure reduction valve near the mains in.... though I guess I then need to consider height to loft tank height. mmmmm

if you fit a reducing valve to the mains in to the house and reduce it to equal the hot water you also reduce your ball valve in the loft to next to nothing, so will take forever to fill.

[theoldboy]

That's what I was thinking.