INLINE FUEL/AIR SEPARATORS
Fuel/Air Separator Gas & Diesel Model #LG100
Racor Fuel/Air Separator Gas Only Model #LG50
Attwood Fuel Vent Line Surge Protector Model #1675
Attwood P-Trap Fuel Surge Protector Model #1689
Inline Fuel/Air Separator Summary
An inline fuel/air separator
is a simple and inexpensive device that is installed directly into
your tank’s overboard vent line. As the fuel tank gets full
and frothy fuel surges up from the tank, a ball rises and cuts off
the travel of fuel that would normally escape overboard via the
vent. Some of these devices claim to help shut off automatic fuel
nozzles when your tank is full. Although none of the devices tested
had a special whistle integrated to indicate fuel level (a feature
we really loved in a now discontinued product) there was still an
audible difference in some of the units when the tank was near full.
The units were easy to install if you have proper access to
your vent line (an ABYC standard). Simply cut a small section
out of the vent line, place the fuel/air separator in the
direction indicated in the instructions and use hose clamps
to secure it.
FUEL/AIR SEPARATOR for GAS OR DIESEL (Model #LG100; retails
for $109.99) At first, we balked at the size of the LG100 (about
the size of an oblong grapefruit). It was the largest of the units
tested and we had just enough clearance to install it. But once
installed, it worked each and every time on our mock-up and our
loaner boat. When the tank became full, it allowed the automatic
shut-off on the nozzle to disengage in plenty of time without venting
fuel over the side or causing backsplash from the deck fill—with
not one spill! We feel that because of its large size, it acted
like a reservoir, allowing for additional room for fuel expansion.
The larger size of this unit also provided the opportunity for fuel
to settle before returning it to the tank and giving the nozzle
time to click off. It works well with either gasoline or diesel
and was the only product in our testing line up that could be taken
apart if necessary. For these reasons, the Racor LG100 was the STAFF
PICK for Foundation Findings #40. It can be ordered through BoatU.S.
and West Marine stores, internet and catalog sales.
RACOR FUEL/AIR SEPARATOR for GAS OR DIESEL (Model #LG100)
RACOR FUEL/AIR SEPARATOR
for GAS ONLY (Model #LG50; retails for
$92.99). The Racor LG50 is the smaller, gasoline-only version of the
Racor LG100 and is about the size of a large salt shaker. It functions
the same way: a ball rises within the housing, preventing vented fuel
from exiting the tank. However, this unit did not work as well as
its bigger brother. It could not be disassembled, so we couldn’t
tell exactly what was going on, but we surmised that the ball would
float up as designed but would block the fuel and air too rapidly.
This sudden shut off of fuel and air to the overboard vent surprised
us when it caused backsplash through the deck fill, even when filling
at the slower speed of 10 gpm. For the 20 gpm test, the backsplash
was even more prominent, which was also true with the other smaller
devices in this category. The Racor LG50 can be ordered through BoatU.S.
and West Marine stores, internet and catalog sales.
RACOR FUEL/AIR SEPARATOR for GAS ONLY (Model #LG50)
FUEL VENT LINE SURGE PROTECTOR (Model #1675;
retails for $23.99). This was the smallest of the inline devices
we tested, about the size of a roll of quarters. This device is
a gasoline-only model (no diesel model is available), but we were
told by the manufacturer it is compatible with diesel as well. However,
when we tested it with the soapy “gasoline” mixture
at 10 gpm, this device did not allow the nozzle to click off in
time and fuel bubbled from the deck fill and overflowed onto the
deck. When we tested this device at 20 gpm, it “overpowered”
the unit causing some minor spillage through the overboard vent,
and a significant amount of backsplash from the deck fill. In fact,
during our onboard boat test later, we witnessed a column of fuel
about three inches in height and two inches in diameter shoot up
from the deck fill when the tank became full. In both testing situations,
the device made some gurgling noises to indicate a rise in fuel,
so a prudent mariner should heed this audible cue and slow down.
This product is available at BoatU.S. and West Marine stores, internet
and catalog sales.
Above: ATTWOOD FUEL VENT LINE SURGE PROTECTOR (Model #1675)
P-TRAP FUEL SURGE PROTECTOR (Model #1689;
retails for $21.54). This unit looks different because it combines
a fuel separator, fuel vent and flame arrestor in one unit and is
roughly the size and shape of a fist. The Attwood P-Trap is installed
on the inside of your hull with the vent portion replacing your
existing overboard vent on the outside of your hull. Since this
unit is plastic, we were concerned about the possibility of crushing
it on a piling in a docking maneuver. To test, we again delivered
fuel at 10 gpm and 20 gpm and the results were that as the unit
suddenly prevented fuel from escaping overboard, backsplash from
the deck fill occurred. With high speed fuel delivery, the pressure
even slightly “overpowered” the unit, causing a simultaneous
leakage of fuel overboard from the vent and fuel overflow on deck.
The Attwood P-Trap Surge Protector is available through the BoatU.S.
and West Marine catalog sales special orders department.
ATTWOOD P-TRAP FUEL SURGE PROTECTOR (Model #1689)
Separator Summary: We discovered a very
disturbing trend with most of the inline devices tested. For most
of the units, pumping at 10 gpm until the automatic shut-off nozzle
clicked off caused fuel to bubble over the mock-up’s deck.
The results were even more disastrous when we pumped at 20 gpm.
Due to the sudden blockage of the vent by the rising ball in the
inline separators, fuel (mixed with air), was then forced out of
the actual filler hole!
Above: Due to the sudden blockage of the vent by the rising ball in the inline separators, fuel (mixed with air), was then forced out of the actual filler hole!
We did not slow
down our pumping, even when we heard gurgling, which may account
for some of the less than positive results. But since many people
lock the pump handle and walk away, we felt that filling at full
speed simulated a realistic situation. For these reasons we do not
recommend using a hands-free device and we do recommend keeping
your hands and face clear from the filler hole.
In general, the larger
the unit and the slower you pumped, the better these devices performed.
The fact is, there is simply is no substitute for careful and deliberate
fueling. Listen to these devices, know how much fuel you need and
slow down when you think you are near full. Do not top off and these
devices may suit you just fine.