Containment sump testing: the 3-year test and the annual check
Containment sumps used for interstitial monitoring of piping have to be tested for tightness at least every 3 years, unless they're double-walled and you check between the walls at least as often as your walkthroughs. Every containment sump also gets a visual check once a year. (40 CFR 280.35; 280.36)
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What a containment sump is
A containment sump is "a liquid-tight container that protects the environment by containing leaks and spills" from piping, dispensers, pumps, and related parts (40 CFR 280.12). The rule names three locations:
- Tank top or submersible turbine pump (STP) sump, over the tank where the pump and piping connect
- Under-dispenser containment (UDC), under each dispenser
- Transition or intermediate sumps at other points in the piping run
Sumps can be single-walled or double-walled (40 CFR 280.12). Any new dispenser system installed after April 11, 2016 needs under-dispenser containment (40 CFR 280.20(f)).
Which sumps need the 3-year test
| Sump | Federal requirement |
|---|---|
| Used for interstitial monitoring of piping, single-walled | Tightness test at least every 3 years by vacuum, pressure, or liquid testing |
| Used for interstitial monitoring of piping, double-walled | Check between the walls at least as often as your walkthroughs instead. Stop checking, and you have 30 days to test |
| Not used for interstitial monitoring | No federal 3-year test, but still part of the yearly walkthrough |
Source: 40 CFR 280.35(a)(1). Tanks in use on or before October 13, 2015 needed the first test by October 13, 2018; newer systems comply from installation.
The test has to follow the manufacturer's requirements, a recognized code of practice such as PEI RP1200, or your state's method (40 CFR 280.35). Many states test more sumps than the federal minimum, so check yours.
How the hydrostatic test works
Most sump tests are hydrostatic: fill the sump with water, wait, and measure whether the level drops. These are the two tests described in a 2022 National Tanks Conference presentation on PEI RP1200 (Kubinsky, National Tanks Conference 2022):
| Test | Water level | Passes if |
|---|---|---|
| High-level hydrostatic | 4 inches above the highest penetration or sidewall seam, or within 1 inch of the top | Visual inspection is good and the level drops less than 1/8 inch in an hour |
| Low-level hydrostatic | 4 inches above the sump sensor's activation level | Visual inspection is good, the sensor or float shuts down the pump or dispenser as it should, and the level drops less than 1/8 inch in an hour |
The steps:
- Visually inspect the entire sump. A visible crack or hole fails without a test.
- Isolate the piping interstitials so test water can't get into the space between the pipe walls (Kubinsky).
- Add water to the test level.
- Wait 15 minutes for the sump walls to settle, then measure the level (Kubinsky).
- Wait an hour and measure again.
Field note: The high-level test is the one I run most.
The low-level test also proves the sump sensor works: a sensor wired to the tank gauge has to shut down the pump serving that sump, and a stand-alone sensor has to shut down the dispenser or pump (Kubinsky). For sensors and the yearly equipment test, see release detection.
The yearly walkthrough check
Once a year, every containment sump gets a visual check: look for damage, leaks into the sump, or releases to the environment; remove liquid (in contained sumps) or debris; and on double-walled sumps with interstitial monitoring, check between the walls (40 CFR 280.36). It's on the walkthrough checklist.
Field note: I find water or fuel sitting in sumps on walkthroughs quite often.
Records
Keep test records for 3 years. If you skip testing because the sump is double-walled and monitored, keep documentation of that for as long as you monitor it (40 CFR 280.35(c)). Walkthrough records are kept for 1 year (40 CFR 280.36(b)).
What fails
- Penetration boots and seals where piping and conduit pass through the sump wall
- Sidewall seams and cracks in the sump body
- Sensors that don't activate or don't shut the pump down
- Lids and covers that let water in, filling the sump
Field note: Those are the failures I see on the sump tests I run.
A failed sump has to be repaired and retested, or replaced. For spill buckets, which are tested on the same 3-year schedule, see spill bucket testing.
FAQ
Does every sump need the 3-year test?
No. The federal 3-year test applies to containment sumps used for interstitial monitoring of piping (40 CFR 280.35). Every containment sump still gets the yearly walkthrough check (40 CFR 280.36). Your state may test more.
What do I do with the test water?
It has been in contact with fuel residue, so handle and dispose of it properly, the same as spill bucket test water. Don't dump it on the ground.
My sump has water in it. Is that a release?
Liquid in a sump can be a sign of a leak, so investigate it, remove it, and find where it came from. The yearly walkthrough calls for removing liquid in contained sumps and checking for leaks into the sump (40 CFR 280.36). Liquid in the interstitial space of a secondarily contained system is an unusual operating condition you may have to report (40 CFR 280.50).
Sources
- 40 CFR 280.35, periodic testing of spill and overfill prevention equipment and containment sumps (Cornell LII)
- 40 CFR 280.36, walkthrough inspections (Cornell LII)
- 40 CFR 280.12, definitions (Cornell LII)
- 40 CFR 280.20, performance standards for new UST systems (Cornell LII)
- 40 CFR 280.50, reporting of suspected releases (Cornell LII)
- Edward Kubinsky, CROMPCO: UST testing, National Tanks Conference (2022)
This guide is general information. Your state UST program decides what's required at your site.