Most OSVs must be mounted no more than three feet (3’) above the
lowest point in the oil line connecting the OSV to the fuel unit!
Anti-siphon Valves
Anti-siphon valves are
similar to fuel safety valves
in that they reduce fire
hazards and prevent fuel
spills caused by fuel being
siphoned from the tank.
Anti-siphon valves automatically
shut off the fuel flow
32 National Oilheat Research Alliance
in the event that a leak occurs in the fuel
line between the anti-siphon valve and
the burner.
These valves are NOT designed to
reduce pressure on systems with booster
pumps.
Anti-siphon valves should be considered
when an UST has been replaced with
an outdoor AST and the burner is in a
basement.
For additional information see manufacturers’
instructions:
Oventrop: oventrop.co.uk
Preferred: preferredutilities.com
Check Valves
Check valves are designed to eliminate
the reverse flow of fuel in a line
and are not normally needed on properly
operating heating systems.
Check valves were often used to
compensate for deficiencies in fuel
lines such as suction leaks due to bad,
porous, loose or leaky fittings. They
are sometimes installed on jobs where
the unit “lost prime” for a variety of
reasons.
It was also a common practice to install
check valves when two burners were connected
to a single fuel line.
In general, check valves should not be
needed to maintain a primed pump. The majority
of systems operate on a ‘gravity’ flow. For
sites that have a lift, the internal check of the
fuel pump should be sufficient to hold prime
unless the lift is excessive. If the pump experiences
lost prime, it is typically an indicator of a
line leak or a bad pump.
Gravity feed installation example, central
system with PRV Valves - OSV valve