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Tank and Piping Release Detection in Petroleum Storage Tank Systems

Learn about release detection requirements, release detection inspections and testing, what to do if you suspect a release, and what records to keep for underground storage tank systems.

Why You Need Release Detection

Release detection helps you know if your underground storage tank (UST) system is leaking below ground—you do not need it for dispensers or aboveground equipment. Aboveground storage tanks are also regulated as a UST system if 10 percent or more of the total volume of the tank(s) and connecting piping is underground. All UST systems must have an approved release detection method and must check it at least every 30 days.

Release detection helps you prevent or minimize releases of regulated substances, such as gasoline, diesel, and used oil, into the environment. These releases can not only contaminate soil and groundwater, but also cost you in lost product and remediation expenses.

Rules for PST release detection are in Title 30, Texas Administrative Code, (30 TAC) Section 334.50 .

Out of Service USTs

If there is still product in the system, you still need to keep release detection. If the system meets the standards for an empty, temporarily out of service UST, you do not need release detection. Temporarily out of service USTs are defined in 30 TAC 334.54(d) .

Using Certified Equipment

A third-party must certify that all equipment you use for release detection meets U.S. Environmental Protection Agency standards. Certifications must list the equipment’s limitations and conditions of use. Keep copies of these in your records while the equipment is in use at your facility.

Release Detection Options

There are many types of release detection methods, but we listed three below that we commonly receive questions about. See our Adobe Acrobat PDF Document Release Detection and Inventory Control for USTs module (RG-475g) of the PST Super Guide (RG-475) for in-depth information about options for tanks and piping.

  • We do not have a preferred method of release detection.
  • For more information about inventory control, see the Inventory Control for PSTs

Continuous Statistical Leak Detection (CSLD)

CSLD test results are acceptable for tank release detection if the test measures a 0.2 gallon per hour rate. Test periods require several hours where no product is added to or removed from the tank, and the test will fail or give an inconclusive result if the product level changes or is too low.

Interstitial Monitoring

Tanks and piping installed after January 1, 2009, must have secondary containment and you must use interstitial monitoring as their primary release detection method.

30-Day Tank Gauging

30-day tank gauging is only acceptable for emergency generator tanks. Measure the product level during a period when nothing is added to or removed from the tank—once at the beginning and again at the end. The difference between measurements should be within certain standards based on the capacity of your tank.

See the end of our Adobe Acrobat PDF DocumentRelease Detection and Inventory Control for USTs module (RG-475g) of the PST Super Guide (RG-475) for a 30-day tank gauging tracking sheet.

Converting Inches to Gallons

The conversion is specific to the type of tank you have. Contact your tank manufacturer to see if they have a chart available.

When Release Detection Goes Down

Keep a written record that the system was broken and repaired. Do not estimate readings for those days. You can still reconcile your inventory control with a few days missing. If you fail inventory control for two 30-day periods, follow the procedures for a suspected release.

Tests and Inspections

30-day Walkthrough Inspections

You must conduct and document a walkthrough inspection every 30 days to make sure your release detection equipment is functioning correctly.

Check for things like:

  • Erratic behavior of product dispensing equipment.
  • Sudden loss of product from the UST system.
  • Unexplained presence of water in the tank.
  • Up to date release detection records.

While there is no required form for these inspections, view an example of a 30-day inspection log in the UST Compliance Notebook (RG-543).

Annual Inspections

You must perform inspections and tests each year to make sure your release detection equipment works properly. The table below lists the equipment and associated tests and inspections you must conduct.


Tests and Inspections

Automatic tank gauge and other controllers

Test alarm and battery backup; verify the system’s configuration.

Probes and sensors

Inspect for residual buildup; test alarm operability and communication with controller; ensure floats move freely, shaft is not damaged, and cables are free of kinks and breaks.

Automatic line leak detector

Test operation to meet criteria in 30 TAC 334.50(b)(2)(A)(i) by simulating a leak.

Vacuum pumps and pressure gauges

Ensure proper communication with sensors and controller.

Hand-held electronic sampling equipment

Ensure proper operation.

Perform tests using the manufacturer’s instructions or Petroleum Equipment Institute’s publication RP1200 Recommended Practices for the Testing and Verification of Spill, Overfill, Leak Detection, and Secondary Containment Equipment at UST Facilities. RP1200 is available for purchase online through several vendors—we cannot provide copies.

Piping Tests

Your requirements depend on whether you have pressurized or suction piping. See page 6 of our Adobe Acrobat PDF DocumentRelease Detection and Inventory Control for USTs module (RG-475g) of the PST Super Guide (RG-475) for details.

Suspected Releases

If you see signs of unusual operating conditions, or your release detection results are inconclusive or failing, you may have a release. Report suspected releases to TCEQ within 24 hours and investigate them within 30 days.

To report a suspected release, complete a Microsoft Word Document PST Incident Report Form (TCEQ Form 20097) and either:

  • Submit by:
  • Call TCEQ Remediation Division at 512-239-2200 and provide the information from the form.

More information on suspected releases and leaking PSTS:

Releases vs Spills

Spills occur specifically during the transfer of a regulated substance (such as fuel) to or from an underground or aboveground storage tank. Spills and overfills occur mainly from bad filling practices. With few exceptions, you must have spill and overfill prevention equipment as part of your UST system.

A spill or overfill that meets either of the following conditions must be treated as a confirmed release:

  • Results in a release into groundwater, surface water, or subsurface soils that exceeds 25 gallons or causes a sheen on nearby surface water.
  • Is less than 25 gallons and cannot be cleaned up within 24 hours of the spill.

See our spill and overfill prevention webpage for more information on spills.


Keep all testing and monitoring results for at least 5 years.

Keep copies of third-party certifications for any release detection equipment for as long as the equipment is in use at your facility.

Our UST Compliance Notebook (RG-543) can help you gather and organize your records.

Electronic Records

Many release detection methods record tests electronically, but we recommend saving printed copies just in case technology fails the day of your inspection. If you prefer keeping only electronic records, call your regional office to discuss this with that office’s investigators.

More Information

See the following resources for more on PST rules and requirements:

TCEQ's Small Business and Local Government Assistance section offers free, confidential help to small businesses and local governments working to follow state environmental regulations. Call us at 800-447-2827 or visit our webpage at