Owners and operators of
regulated underground
storage tanks (USTs) on tribal
lands must comply with the
federal UST regulation.
This compliance assistance
brochure highlights tips
for overfill prevention.
Note: This document is a
resource to promote
compliance and does not
replace the federal UST
regulation.
This brochure is one in a
series of EPA compliance
assistance brochures
designed to help owners and
operators in Indian country
comply with the federal UST
regulation.
Other brochures focus on
implementation, compatibility
spill buckets,
recordkeeping and
notification, financial
responsibility, insurance, tank
release detection, and piping
release detection.
www.epa.gov/ust/publications-related-
underqround-storaae-tanks

Maintain
v>EPA
Office of Underground Storage Tanks
www.epa.aov/ust
May 2017
EPA-510-F-17-006
Compliance Assistance in
Indian Country

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OVERFILL PREVENTION
Overfill prevention is required for every
underground storage tank (LIST) filled with
more than 25 gallons of product at one time.
It is installed inside your tank to stop product
flow, reduce product flow, or alert the delivery
person during delivery before the tank
becomes full.
There are three common types of overfill
protection, as shown below:
Overfill alarm	Automatic shutoff Flow restrictor
device	(ball float valve)
(flapper valve)
If a tank is overfilled, product could be forced
through the vent line and other loose tank
fittings, potentially resulting in a release into
the environment. Properly functioning overfill
prevention will significantly reduce the
chance of an overfill release.
Inspect your overfill prevention equipment every
three years to ensure it will function properly to
prevent overfills.
What can you do to prevent
an overfill?
Repair or replace improperly functioning
overfill alarms
Alarms alert the
delivery person that
product is reaching a
certain level in the tank.
They also give the
delivery person enough
time to shut off product
flow to avoid a potential
release.
Alarms must be
located where the
delivery person can
easily see or hear
them.
If you hear the alarm,
ensure the delivery
person has stopped
the flow of fuel to the
tank.
Repair or replace improperly functioning
automatic shutoff devices
,rir Automatic shutoff devices stop the flow of
product when the product reaches a certain
level in the tank during delivery.

Automatic shutoff device
with damaged float
Looking down the fill pipe
at the flapper valve
The automatic shutoff device is located in the
drop tube within the till pipe riser.
A qualified UST contractor can check to make
sure that all float components are functioning
properly, and the float arm is not obstructed and
can move freely.
Keep the automatic shutoff valve free and
unobstructed. A disabled automatic shutoff
prevents the valve from closing to prevent an
overfill.
A dip stick is in the drop tube
preventing the shutoff device
from closing.
Inspect the automatic
shutoff device to make
sure it has not been
tampered with, disabled,
or removed from the fill
pipe and there are no
obstructions in the drop
tube that will prevent the
device from operating.
Monitor product deliveries and transfers
w Pay close attention before, during, and after
product delivery to help the delivery person
avoid overfilling your UST.
Immediately report spills to your
implementing agency.
Replace improperly functioning ball float valves
s®* Ball float valves slow product flow by
preventing vapors from leaving the tank when
product reaches a certain level in the tank. This
alerts the driver to stop the delivery. The top of
the tank must be tight during deliveries so that
vapors cannot escape.
^ A qualified UST contractor can check to make
sure the ball float operates properly and moves
freely, the cage is intact, and the ball float air
hole is not plugged.
Ball floats may be used on tanks
installed on or before 10/13/15 as long
as they operate properly.
Ball float valves may not be used
when overfill prevention is installed or
replaced.
Note: Recommended practices say
ball float valves should not be
installed on tanks with: suction
piping, pumped delivery, coaxial
Stage I vapor recovery, remote fill
pipes with gauge openings, or when
shutoff valves are used for overfill
prevention.
Order the appropriate amount of product
** Order only the quantity of product that will
fill 90 percent of the tank.
/	N
The formula for determining the maximum amount of
gasoline to order is:
(Tank capacity in gallons X 90%)- volume of
product currently in tank = maximum amount of fuel
to order
Example: (10,000 gallons X 0.9 ) - 2,000 gallons
= 7,000 gallon maximum amount to order
Ball float valve
with ball out of
the cage
For recommended inspection guidelines, checklists, and tips
for managing your UST system overfill prevention, see EPA's
Operating And Maintaining Underground Storage Tank
Systems: Practical Help And Checklists or order free copies
by calling (800) 490-9198.

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