I have a Hydrotherm two stage Boiler, with a 15psi Watts feeder to the
boiler and an Everhot indirect water tank feeding domestic water via
coil. There is a steel expansion tank, probably a 30 gallon tank.
The issue I have had is that the pressure rises 5 psi or so every two
to three weeks to the 20 psi level and continues to rise after that
point. I have replaced the Watts Feeder, turned the valve off before
it and the problem still exists. I have also replaced the Expansion
Tank drain valve and the problem still exists. I have repeatedly
isolated the Expansion Tank via a shutoff valve, turned the boiler off
(gas burners) and drained it completely, takes about an hour, until
blackish water trickles out of the tank and the problem still exists.
The Watts feeder stops feeding at 15 psi and I turned the valve before
the Feeder off and the pressure still rises 5 psi every two weeks.
If the Everhot Tanks coil has a leak in it wouldn't my domestic hot
water be blackish and wouldn't the pressure in the boiler rise faster
than 5 psi every two weeks?
Could the expansion tank have a leak in it? I don't see a puddle,
could it be a pinhole leak? How do you detect that?