water tank in loft overflow

[sahd]

The tank in my loft is overflowing for about an hour every morning around 6.15am I have had a new valve and ball **** fitted and this has not made any difference, the plumber it's my life style re water usage, how can it be when it only started a week ago, please can anybody suggest another reason and explain why the new valve and ball **** haven't stopped the problem, surely it is like a tap - either off or not working
HELP

[Theland1]

If you have an immersion heater, the copper coil inside might be leaking. I had the same problem, and had to have a new copper tank / immersion heater fitted, that cured the problem. I'm presuming of course that you have central heating that also heats up your hot water?
By the way, it might be best to put this question into home and garden section.

[4getmenot]

I'd get a new plumber

[chas2008]

if the only inlet is the ball **** then that has to be the problem..
there may be another overflow into the main tank, (ie central heating feed tank) in which case if the ballcock is working this is where the problem lies..

[burnhal]

if its only at that time of the morning then I would say the new ball valve is at fault- either its set wrongly such that it doesnt shut off before the water level reaches the overflow or it has a slow drip. During the day you will be constantly drawing off hot water- washing up, bath etc and the hot water tank gets topped up from the cold water tank. However at night the tank will not be periodically drawn from and will get full enough to reach the overflow.

[gasman]

If it is a problem with the Float valve then it would be over flowing all the time not just for an hour in the morning, So most likley the float valve is OK. If it only happens when you have the hot water tuned on to heat up the cylinder first thing in the morning then the indirect coil has corroded in the cylinder itself, This means that all the central heating fluid is mixing with you're hotwater and is a potential bio hazard. the cylinder will have to be changed.

[MrPoliteness]

I know it is a little late now but I think it may well be that you just need a new washer in the ballc0ck. When the float arm rises with the waterlevel it pushes a pin that pushes a washer shut. It is most likely that this rubber has perished and if you unscrew the housing and put a replacement washer in place that will solve the problem.

As other people have mentioned it is down to the fact that you are not using water overnight and the slight drip from the ballc0ck allows the tank to overflow.