pulsacoil header tank filling to overflow

Hi, my first time on a forum, my friends pulsacoil keeps filling the header tank and running to the waste outside. I've checked it's not the ball cock and isolated it to be certain. It's not fast filling and causes a drip from the waste every second if left and not siphoned off. The header tank is warm water too. Can anyone advise me. My friend called a plumber out and he replaced the ball cock and then charged her and she still has the problem.

I've just edited my last post due to my friend informing me incorrectly SORRY. The mains had been turned off during the night and the header tank stopped filling. So I guess there is a leak inside the hot storage tank from the mains? Does this mean a new tank altogether then or am i missing something. The header tank takes about 5hrs to fill from the water line to the waste pipe. Thanks and please help. My friend is worried sick.

More info!! We emptied the header tank out and dried it. Then watched inside the header tank for a short time and seen the steady drip coming from the side entry pipe or down transfer pipe. Thanks for reading :o)

Hi Steve,

Apologies for my delay in replying.

Yes this is a leak in the mains water heat exhanger. The water escapes into the thermal store instead of out onto the floor like with most other leaks so the store just over-fills itself. If this really IS an original Pulsacoil and not a Pulsacoil 2000 or A Class, then the only fix it to replace the appliance. You cannot get access to the leak as it is inside the copper store container.

Cheers, Mike

The plated heat exchanger on a Pulsacoil 3, 2000 and A Class can cause this problem