Overflow leaking from header header tank

[roberts.b11@sky.com]

I have a leak from the overflow from the header tank, it doesnt happen often but normally in the night when no water is being used.I have checked the ball cock in the tank and it is working fine..water shuts off at desired leval.What else could cause the tank to overfill..there is some copper residue in the bottom of the tank..could the hot water tank be to blame...hole in the heat exchanger??..thanks in advance

[htg engineer]

Could be pumping over, is the central heating or hot water on when it overflows ?

htg

[roberts.b11@sky.com]

Could be pumping over, is the central heating or hot water on when it overflows ?

htg

Yes i have my hot water on constant, so there is always a call on the boiler to heat the water 24/7.It happened again last night when i checked the overflow this morning, as i have said the ballcock seems fine, i have bent the arm downwards so it is cutting off sooner as well.What could cause it to be pumping over?I am covered by british gas care 200 but dont know if this is covered? thanks again in advance,

[TheDoctor4]

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