Tank tightness, line tightness and leak detector testing
Tank tightness, line tightness and leak detector tests cover different equipment. Compare their purpose and the Wisconsin reports used for each.
Three tests, three different questions
A work order that says "tank testing" may refer to several jobs. Before booking, identify whether the request concerns the tank, the product piping or the line leak detector. The equipment and the report needed are different.
| Test | Equipment | Question it addresses |
|---|---|---|
| Tank tightness | Storage tank | Does the tank meet the tightness criterion under the test conditions? |
| Line tightness | Product piping | Does the line meet the tightness criterion under the test conditions? |
| Line leak detector functionality | Mechanical or electronic detector | Does the detector respond to the test leak condition as required? |
Tank tightness testing
A tank tightness test evaluates the tank using a method suitable for the installation and product. Test conditions matter: the method must account for factors such as product temperature, vapor pockets and groundwater conditions.
The federal tank tightness performance criterion in 40 CFR 280.43(c) is detection of a 0.1 gallon-per-hour leak rate. That is a method performance requirement, not a statement that any tank with a passing report can never leak. The report applies to the equipment and conditions documented for the test.
In Wisconsin, the tank precision tightness report is TR-WM-152. DATCP also provides TR-WM-155 for pre-operational tank tightness work. The reason for testing determines which work and documentation are needed. USTEX tank testing services.
Line tightness testing
A line tightness test evaluates the product piping. The line configuration and applicable method determine the setup, including the test pressure and which sections are included.
The federal piping rule sets a 0.1 gallon-per-hour detection criterion for line tightness testing, with the specified pressure conditions. Wisconsin documents line precision testing on TR-WM-125. Identify the line and its connected equipment rather than treating all piping at the site as one undifferentiated test.
Line leak detector functionality testing
A line leak detector is equipment that responds to a leak condition. A functional test checks whether that response occurs. Mechanical and electronic detectors use different operating arrangements and must be checked using the procedure that applies to the installed equipment.
Under the federal automatic line leak detector criterion, the device must detect 3 gallons per hour at 10 psi within one hour by restricting flow, shutting off flow or triggering an alarm. That detector criterion differs from the precision line tightness criterion.
Wisconsin uses TR-WM-123 for the detector functionality test. A passing detector test does not, by itself, supply a precision line tightness result. Mechanical and electronic detector testing.
Where annual functionality verification fits
Wisconsin's TR-WM-139 covers underground tank system functionality verification. It records monitoring equipment and the results of the verification performed. The detector, tank precision and line precision forms identify their respective tests separately.
An inspection request should be read by its listed equipment and required work. Do not add a tank tightness test to an annual visit simply because both are called "tank testing." The scope should follow the site's equipment, monitoring method and the reason for the request.
What to send when requesting a test
If the notice does not make the requested test clear, send it with the inquiry. We can discuss the scope before scheduling. Use the Wisconsin visit preparation checklist or request testing.
- Facility address and DATCP facility ID.
- Inspection notice or the item requiring testing.
- Previous tank, line and detector reports, if available.
- Tank products and capacities.
- Detector and monitoring console make and model.
- Current alarms, operating restrictions and deadline.
Forms and scheduling
Find Wisconsin forms on USTEX Guide. For ongoing scheduling, USTCompass keeps facility test dates and reports together.
Sources
- 40 CFR 280.43: tank release detection methods
- 40 CFR 280.44: piping release detection methods
- Wisconsin DATCP: testing and inspection forms
Published October 1, 2026. Source documents checked on that date.