baxi 80e boiler pressurising when cold

[bernard@gbbikeleathe]

When my boiler is cold the system very slowly creeps up to 3bar the the prv valve is dripping.
Top up link has a ball valve and a check valve fitted.
Does not appear to be letting by.
Also we have a cold water storage tank in the loft this keeps dripping ball cock valve not letting by.
Some how the hot water is connected to the hot water system?
we have got mixer taps but I just fitted non return check valves still happening.
Replaced "o"rings and cleaned the diverter vavle made no difference
Could it be the hot water heat exchanger has developed a pin hole inside the exchanger?
Any other thoughts please.

 

[cross thread]

Start by disconnecting filling loop.