It is possible that the O-Ring seal on the DHW switch is leaking. This is caused by a build-up of limescale on the spindle of the switch, so that as the water starts to flow, the spindle, while moving out to operate the switch, wears a groove in the O-Ring and allows it to leak.
However, this should NOT cause a pressure loss in the system, as the two are independent. Maybe there is a leak in the pipework and the water is running down the outside of the pipe and appearing at the switch location.
JR March 2009 |