Combo cylinder tank overflowing

[d welsh]

I have a problem with a combo emersion economy 7 overflow leaking from feed tank at top,I reduced water level and replaced part 2 ballvalve, but 4/5 hours later overflow leaking again,cylinder has no makers name and is covered in fake lookalike leather cover,stopcock in kitchen has pressure gauge above reading 2/half bar,blending valve on side of cylinder Is oventrop manual,customer had new leaver tap fitted in kitchen 6/7 weeks ago ,I isolated hot feed to tap thinking cold feed was maybe bypassing thru in to cylinder then to tank overflow above but after 4/5 hours tank overflow leaking again customer had a bloke round from yellow pages and offered to extend overflow pipe on outside wall in to gutter for around£ 150' but this won't cure fault,she has individual basin taps and shower bath mixer any advice would be welcome

 

[dancinplumba]

Have you turned off mains water ? Sounds like coil holed, water got to come from somewhere

 

[PETE 123]

Water can only come from a tap or mixer letting by or coil pin holed

 

[PhoenixServices]

Isolate the bath/shower mixer to prove its not that. If it's not that isolate the heating tank.

 

[Mike Jackson]

Sounds like it may be a thermal store rather than a cylinder. If so I'd go with coil failed.