There are several warning signs of leaks from USTs or piping. Unusually
strong petroleum vapors, dying vegetation near the tank and erratic equipment
operation (unexplained presence of water in the tank) are all indicators of a
possible release. Tanks that seem to require more fuel than they are using
or experience a sudden loss of product may also be leaking.
Why is release detection crucial?
All regulated tanks and piping must have release detection so that leaks
are discovered quickly before contamination spreads from the UST site. You
must provide your UST system with release detection (often also called leak
detection) that allows you to meet three basic requirements:
- You can detect a leak from any portion of the tank or its piping that
routinely contains petroleum;
- Your leak detection is installed, calibrated, operated, and maintained
in accordance with the manufacturer's instructions; and
- Your leak detection meets the performance requirements described in the
federal regulations (sections
280.43 and 280.44).
The leak detection requirements are summarized in the table below:
|Leak Detection Requirements
|UST System Component
||Leak Detection Method
- Monthly Monitoring*; or
- Monthly Inventory Control and Tank Tightness Testing Every 5
- This option can be used only for 10 years after installing
a new UST
or upgrading an UST with corrosion protection. After
this 10-year period,
Monthly Monitoring is required.
Choice of one from each set A & set B:
- Automatic Shutoff Device -or-
- Flow Restrictor -or-
- Continuous Alarm System
- Annual Line
- Monthly Monitoring*
- Monthly Monitoring* (except automatic tank
Testing Every 3 Years; or
- No Requirements IF the following
characteristics are readily determinable:
- Below-grade piping is sloped so that its contents will drain
the storage tank if the suction is released.
- Each suction line has only one check valve which is located
below the suction pump.
- System must operate at less than atmospheric pressure.
*Monthly Monitoring Choices in the table above include:
Secondary Containment With Interstitial Monitoring
Automatic Tank Gauging
Monitoring For Vapors In The Soil
Monitoring For Liquids On The Groundwater
Statistical Inventory Reconciliation (SIR)
Other Methods Approved by the Implementing
Special note for tanks 2,000 gallons or less in capacity:
Tanks 2,000 gallons and smaller
may be able to use manual
to meet leak detection requirements (be sure
you read the
link carefully to make sure you meet all the requirements of this method).
What leak detection methods can you use to detect leaks from tanks?
Owners and operators of petroleum USTs must use at least one of the leak
methods below, or other methods approved by their state agency.
- Secondary containment and
This involves placing a barrier between the UST and the environment. The
provides secondary containment and can be a vault, liner, or the
outer wall of a
double-walled structure. Interstitial monitoring
methods range from a simple dip
stick to automated vapor or liquid sensors
permanently installed in the system.
All USTs holding hazardous substances
that were installed after December 22, 1988
must use this method.
detailed information on secondary containment and interstitial monitoring.
- Automatic tank gauging (ATG) systems
ATGs use monitors permanently installed in the tank. These monitors are
electronically to a nearby control device to provide information on
and temperature. The gauging system can automatically
calculate the changes in
product volume that can indicate a leaking tank.
This method does not work on
detailed information on automatic tank gauging systems.
- Vapor monitoring
Vapor monitors sense and measure product vapor in the soil around the tank
piping to determine the presence of a leak. This method requires
carefully placed monitoring wells. Vapor monitoring can be
using manual devices or continuously using
permanently installed equipment.
detailed information on vapor monitoring.
- Groundwater monitoring
Groundwater monitoring devices sense the presence of liquid product
floating on the
groundwater. This method requires installation of
monitoring wells at strategic
locations in the ground near the tank and
along the piping runs. To discover if leaked
product has reached
groundwater, these wells can be checked periodically by hand or
continuously with permanently installed equipment. This method is
effective only at
sites where groundwater is within 20 feet of the
detailed information on groundwater monitoring.
- Statistical inventory reconciliation
SIR uses sophisticated computer software to determine whether a tank
system is leaking.
The computer conducts a statistical analysis of
inventory, delivery, and dispensing data
collected over a period of time
and provided by the operator to a vendor.
detailed information on statistical inventory control.
- Manual tank gauging
Manual tank gauging can be used only on tanks 2,000 gallons or smaller.
does NOT work on tanks larger than 2,000 gallons or on piping.
This method requires
taking the tank out of service for at least 36 hours
each week to take measurements of
the tank's contents. Tanks 1,000 gallons
or less can use this method alone. Tanks from
1,001 to 2,000 gallons can
use this method only when it is combined with periodic tank
testing and only for 10 years after installing a new UST or upgrading an
with corrosion protection. After 10 years, these USTs must use one of
the leak detection
methods listed above in 1-5.
detailed information on manual tank gauging.
The additional method below can be used temporarily at petroleum UST
- Tank tightness testing and
This is a combination of two methods. Tank tightness testing requires
conducted by vendors who temporarily install special
equipment that tests the
soundness of the tank. Tank tightness testing
must be used in combination with
inventory control. Inventory control
requires taking daily accurate measurements of
the tank's contents and
performing monthly calculations to prove that the system is not
Tank tightness testing and inventory control can be used only for 10 years
installing a new UST or upgrading an UST with corrosion protection.
After 10 years, these
USTs must use one of the leak detection methods
listed above in 1-5.
More information on tank tightness testing combined with monthly
What leak detection methods can you use to detect leaks from piping?
Pressurized piping must meet the following requirements:
If your UST has suction piping, your leak detection requirements will depend
on which type
of suction piping you have.
- If you determine that your suction piping has characteristics listed
below, your piping
may not need leak detection.
- Below-grade piping operating at less than atmospheric pressure is
sloped so that
the piping's contents will drain back into the storage
tank if the suction is released.
- Only one check valve is included in each suction line and is located
the suction pump.;
- Suction piping that does not exactly match the characteristics noted
above must have leak
detection, either monthly monitoring (using one of
the monthly methods noted above for
use on pressurized piping) or tightness
testing of the piping every 3 years.
More information on leak
detection for underground piping is available.
Why might you fail to be in compliance even if you have the required leak
detection equipment or method?
It takes more than equipment to be in compliance and to have a safe
facility. You must operate
and maintain this equipment properly over time or
you will not benefit from having the
equipment or using an approved leak
detection method. Most importantly, you must be sure
you successfully use the
method at least once a month to determine if the UST system has
of its contents.
Failure to operate and maintain equipment and methods can lead to new
releases. For example,
a poorly functioning ATG system will provide inaccurate
data that will be useless in detecting
leaks. A manual vapor or groundwater
monitoring device that doesn't work properly means
you have no reliable leak
detection system. Inaccurate data from poorly operated and maintained
measuring devices can make SIR methods unable to usefully detect leaks in a
If your leak detection fails, you may incur fines or penalties
for noncompliance, as well as an
expensive cleanup at your UST site.
Be sure you review and use the information sources on our
And Maintaining UST Systems Web pages.
Are reporting and recordkeeping necessary?
If operation of the leak detection method indicates a possible leak, UST
owners and operators
need to report
the potential release to the regulatory authority. UST owners and
records on leak detection performance and upkeep. These include the
monitoring results, the most recent tightness test results,
performance claims by the leak
detection device's manufacturer, and records of
recent maintenance and repair.
How can publications on leak detection help you?
To assist owners and operators in conducting
proper leak detection, OUST has developed
several publications that are
available on our Web site for viewing, downloading, printing,
These publications clearly present leak detection requirements to UST owners
Maintaining UST Systems:
Practical Help And Checklists (see sections on
Straight Talk On
Leak Detection Methods For Petroleum Underground Storage Tanks And
Doing Inventory Control
Right For Underground Storage Tanks
Introduction To Statistical
Inventory Reconciliation For Underground Storage Tanks
Manual Tank Gauging For
Small Underground Storage Tanks
Getting The Most Out Of
Your Automatic Tank Gauging System
You may also want to use the following resources:
Many other publications are also available for viewing, downloading,
printing, or ordering at