Another possibility is the non return valve has some sort of growth or muck
in it, preventing it form seating 100. The cleaning may have cleared some
of it, resulting in a better seal, but not yet perfect. If you have access
to the non-return valve, I would remove it and give it a clean


"Rick" wrote in message
ink.net...
TSailor wrote:

The presence of a leak is obvious, but why would it get better after
cleaning the system?

First, to put paid to a really silly bit of voodoo engineering, since
the pressure switch is on the discharge side of the pump, and your pump
contains a check valve to separate suction and discharge, and your boat
probably has a water system that operates above atmospheric pressure,
any air in the system could only enter the suction side of the pump and
therefore have zero effect on cycling. If the pump can create enough
pressure to cycle off, it is also compressing what little air might be
introduced to the suction side. If you are not getting air out of your
taps you are not getting it into the system.

It is likely that cleaning the system produced a bit of sludge that was
forced by system pressure into the area of the leak. Sort of like those
car radiator leakstop chemicals that rely on the leak itself to
transport the sealant.

Check the insulation around the heater and see if it is damp. The leak
must be quite small and what little water leaks out is probably mostly
evaporating due to the heat of the tank. Check around the heating
elements and other fittings.

Rick