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Temporarily Out of Service Tanks

How to take underground storage tanks (USTs) temporarily out of service and the requirements for these tanks.

You can have active tanks on the same site as a TOOS tank if all tanks meet the requirements for their status.

Taking Tanks Temporarily Out of Service (TOOS)

Take tanks temporarily out of service if you are not currently using them, but not ready to permanently remove them. Make sure they meet all requirements for TOOS tanks, then:

Empty TOOS Tanks

You can take tanks out of service temporarily even if they still hold regulated substances. However, you should consider emptying the tank while it is not in use to reduce the risk of accidental releases. Releases can lead to costly remediation and cleanup fees.

Your system is empty if you have removed all regulated substances as completely as possible and any residue:

  • Is no more than 2.5 centimeters at the deepest point.
  • Does not exceed 0.3% of the system’s weight at full capacity.
  • Will not pose an unreasonable risk to human health and safety or the environment if accidentally released.

Annual Registration and Self Certification

If they still contain a motor fuel submit your registration and self-certification form annually. If your system is empty, then you only need to do so when taking the tank out of service temporarily and again when returning it to service.

Financial Assurance

You must also still provide financial assurance annually, unless the tank is empty and you have conducted a site check.

For example:

If your tank is TOOS but contains a regulated substance: submit financial assurance documentation with your annual registration and certification.

If your tank is empty and TOOS, but you have not conducted a site check: keep documentation of current financial assurance with your records.

If your tank is empty, TOOS, and you have conducted a site check: you do not need financial assurance.

Tank Maintenance Requirements

Even if you are decommissioning the tank or preparing it for permanent removal, while it is out of service, you must:

  • Keep all vent lines open and functioning to prevent vapors building up, which can cause explosions.
  • Cap, plug, or lock piping, sumps, manways, tank access points, and ancillary equipment to prevent access, tampering, or vandalism by unauthorized persons.
  • Always maintain corrosion protection and system equipment.
  • Maintain operator training requirements and continue retraining every 3 years.

If you have not emptied the UST(s) and performed a site check, you must also maintain an approved release detection method and financial assurance.

Suspected or Confirmed Releases

Report suspected releases to us within 24 hours and investigate them within 30 days. If you confirm a release, you must take corrective actions.

System Equipment Inspection

You must maintain the system so that it could be brought back into service, but you do not need to keep a log of inspections. If you have water in spill buckets and corroded fill tubes, you could be cited for a violation. Different requirements apply if the tanks are empty.

Bringing a TOOS Tank Back into Service

Send us a completed Aboveground and Underground Storage Tank Construction Notification (TCEQ form 00495) at least 30 days before you plan to return the tank to service.

If your system was out of service for more than six months, have a certified technician complete tank and piping fitness tests to detect a release as small as 0.1 gallon per hour.

Tanks brought back into service must:

  • Use an approved method of release detection.
  • Have acceptable financial assurance.
  • Use approved methods of spill and overfill prevention and control.

Send an updated UST Registration and Self-Certification (TCEQ form 00724) within 30 days of returning the tank to service.


Keep the following records for at least five years after taking the system temporarily out of service:

  • Date of temporary removal from service.
  • Name, address, and phone number of any person who prepared your system for temporary removal from service.
  • Procedures used to prepare and empty the system.
  • Any requests for, and approvals of, extensions of time.

When you return the system to service, keep records of:

  • Date system was returned to service.
  • Name, address, and phone number of the person who conducted the tank and piping tightness tests.
  • Results of the tank and piping tightness tests.

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