Check valves should NOT be used with gravity feed systems!
National Oilheat Research Alliance 33
There are several disadvantages associated
with check valves:
• they increase vacuum and reduce the
distance that fuel supply lines can be run
• depending on where they are located,
they can cause turbulence and strip air
from the fuel resulting in dirty and noisy
combustion
• when used in single pipe systems or systems
supplied by boost pumps, they can
cause fuel leaks due to thermal expansion.
In these situations, a thermal relief
valve may be required. See below for
additional information
Check valves are normally available in two
styles:
HCV, identified
by its silver cap,
incorporates a soft
elastomer seat and
is recommended
for a tight shut-off
needed to eliminate
reverse flow.
CV, identified by
its brass cap, is the
hard seat model that
utilizes a stainless
steel ball and is not
designed for absolute
reverse shut-off.
Foot Valves
Foot valves are designed to assure that pump
suction lines remain “primed” by preventing
the flow of fuel back to the tank when the
pump is inoperative. Foot valves are installed
inside fuel tanks at the bottom of the suction
line.
Foot valve are sometimes found in use with
older buried fuel tanks, they are no longer commonly
found in residential tanks because the
internal check valve of the fuel unit is generally
sufficient to hold the prime in fuel lines.
The possible presence of a foot valve is one
of several reasons why CO2 cartridges should
never be used to clean clogged lines.
Thermal Shut Off
(Fusible) Valves
Fusible valves minimize fire hazards by automatically
closing when ambient temperature
reaches potentially hazardous levels.
They employ
a fusible
element in the
hand wheel
that “melts” at
165°F, closing
the valve
and preventing
the flow of
fuel. Fusible
valves look like
a small globe
valve and can
be operated as a
manual shutoff
for servicing the
system. They are
utilized at tanks,
filters, fuel units,
de-aerators and where lines from outside tanks
penetrate the building.
NFPA 31 requires that fusible valves be
installed on all oilheat systems.
Solenoid valves
Solenoid valves are sometimes referred to as
magnetic fuel valves or delayed fuel valves and
there are several types that a service technician
is likely to encounter.