Water Heater Pressure Relief Valves
found that these valves are much more likely to open on boats than
the ones in houses. This can be caused by the fact that many boats
have water heaters that operate not only by electricity like those
in homes, but also with a heat exchanger through which the hot
water in your engine passes to heat the water in the hot water
less temperature control with this system than with an electric
thermostat controlled heating element, so there’s
more of a likelihood of higher pressure occurring from time
with varying sources of water going into your boat’s
tank, there’s more likely to be grit or other impurities
in the water. Once these valves open just a tiny bit, to let
off a tiny amount of excess pressure, they will often continue
to leak. This is because of particles of grit that may get
trapped in the valve seat. Also, the springs on the valves
can weaken with use or simply from age.
water heater makers such as Raritan have anodes within the
units which should be replaced from time to time. This can help
to minimize possible electrolysis that could harm the tank and
impair the valve, which probably contains dissimilar metals as
compared with the rest of the tank.
these valves will open only when the tank is being
heated, as is normal when you’re plugged in, have a generator
going, or are underway and have a tank that’s equipped
with a heat exchanger.
unlikely that these valves will open with just the pressure
from the boat’s water pump or connected dock water pressure,
because this isn’t nearly enough pressure to overcome the
spring, but sometimes the valve becomes weak or damaged enough
for this to happen.
Relief Valves are usually easy to replace although their manufacturers
recommend having a qualified professional do it. If you do it
yourself, read and follow carefully all warnings and instructions
from involved manufacturers including that of the valve and hot water
tank. Also follow all relevant codes and standards. Don’t get
valves that exceed temperature and pressure ratings for your system.
Mistakes can cause such things as electrocution and severe burning.
a spare aboard with temperature and pressure limits as recommended
by tank manufacturer or other relevant authorities. Remember, you’d
much rather have this awaken you in the night than suffer the results
of a bursting hot water system.
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Copyright 2004-2010 Tom Neale