DIY Doctor UK DIY Forums

The overflow on the cold storage tank (which feeds the DHW tank) keeps overflowing - I have set the ball cock so it cuts off the mains cold water at half capacity so it must be filling up from the hot water vent pipe. why is it doing this. I'd like to stop this quickly as when it overflows it make a real mess on the (flat) garage roof.

sounds like your boiling over through the open vent. Turn your pump down one speed and turn you thermometer down. that should help