T&T: water system issues

[Peter Bennett]

Tuesday, July 8, 2008, 8:12:43 PM, ed wrote:

e> My new to me 1985 boat has fresh water system issues I'm trying to sort out.
e> After running the engine a while, I get hot water out the cold water 
e> faucets. The hot water tank has an engine heat system. I'm thinking I need a
e> check valve on the water inlet side of the hot water tank to keep hot water
e> from backing into the pump.

On my boat, the water tanks, pump and most of the plumbing are all in
the engine compartment - after running, the "cold" water is quite hot,
but not nearly as hot as the "hot" water.  Running the cold tap for a
short time will bring cooler water.

It seems that a check valve at the input of the water tank, plus an
expansion tank somewhere on the hot side of the check valve seems to
be recommended. On a previous boat, I had a check valve, but no
expansion tank, so the safety valve on the water tank (or a weak joint
in the plumbing) leaked as the engine heated the water in the hot
water tank.

If you don't have a check valve, but do have an expansion tank, you
will get some hot water pushed back into the cold system, but it
shouldn't develop enough pressure to damage the pump.


-- 
Peter Bennett, VE7CEI    Vancouver, B.C., Canada
Ennos 31 "Honeycomb"
GPS and NMEA info: http://vancouver-webpages.com/peter 
Vancouver Power Squadron: http://vancouver.powersquadron.ca