DEEP: Underground Storage Tanks Serving Five or More Residential Units

Underground Storage Tanks (USTs) Serving Five or More Residential Units

Residential vs. Nonresidential
A “Residential underground heating oil storage tank system”, as defined by statute, heats "four (4) residential units or fewer”.  DEEP does not regulate residential heating oil USTs.

If an UST is used to heat five (5) or more residential units, that UST is “nonresidential”, even though people live there. 
Heating oil USTs under 2100 gallons
  • Construction: USTs and piping installed on or after October 1, 2003, must be double-walled.  There must be a sensor between the walls to detect a leak (continuous interstitial monitoring).  USTs must be fiberglass-reinforced plastic (FRP), cathodically protected steel or composite (fiberglass-clad steel).
  • Property Sales: Disclose all information about the UST (age, construction, location, etc.) to the buyer at least 15 days prior to closing.
  • UST failures (leaks from any part of the tank or piping) must be reported to DEEP immediately.
  • Clean up heating oil pollution promptly. 
Heating oil USTs 2100 gallons or larger
  • Construction: USTs and piping installed on or after October 1, 2003, must be double-walled.  There must be a sensor between the walls to detect a leak (continuous interstitial monitoring).  USTs must be fiberglass-reinforced plastic (FRP), cathodically protected steel or composite (fiberglass-clad steel).
  • Fee: There is a $100.00 per tank installation fee ($50.00 for municipalities).
  • Annual notification is required under Connecticut General Statute (CGS) section 22a-449(e).  Please note that heating oil tanks used for onsite heating are exempt from the annual fee at any volume.
  • Property Sales: Disclose all information about the UST (age, construction, location, etc.), including a copy of the annual notification, to the buyer at least 15 days prior to closing.
  • Life expectancy is the manufacturer’s warranty period.  FRP, cathodically protected steel, and composite USTs must be removed by the end of their warranty period, usually 30 years.  Unprotected steel USTs are beyond their life expectancy and must be removed.
  • Testing:
    • FRP USTs are required to be tested 3 times:
      • 3-6 months after installation and
      • 2 years and 1 year before the end of life expectancy (usually at 28 and 29 years).
    • Cathodically protected steel and composite USTs are required to be tested twice:
      • 2 years and 1 year before the end of life expectancy (usually at 28 and 29 years).
  • UST failures (leaks from any part of the tank or piping) must be reported to DEEP immediately.
  • Clean up heating oil pollution promptly.
For more information, contact the Storage Tank Enforcement Unit at (860) 424-3374.


Content last updated December 14, 2016