Civil-Environmental Engineering

Frequently Asked Questions*

This test is best performed after the tank is in place in the excavation and leveled, with the risers installed and sealed, but before it has been backfilled.  Most counties will require that the test be witnessed by their inspector, but if scheduling is a problem, some will accept another witness, such as the project engineer (check with the county first).  Either way it's a good idea to 'already know the answer before you ask the question', as the lawyers say.  In other words, you might consider the wisdom of trying this first, yourself, before you invite the inspector to be present:

  • Do this test before removing the factory installed knock-outs for both the inlet and outlet.  The idea is to test the tank, not the attached lines; and it can be real hard to reseal these openings as well as the factory already has.
  • Make a mark with a broad-tipped indelible marker (so that it is clearly visible) at least 2" above the top of the tank, inside the riser.
  • Fill the tank with water to the mark.
  • Photograph the water level at the mark with a camera that records the time and date, for documentation.
  • Do the same thing again, 24 hours later to show that there has been no leakage.

Some counties will allow up to 1% leakage.  That would be 15 gal. on a 1500 gal. tank, or a drop of 3-3/4" if you have two 24" risers.  So obviously, if the project is in a county that allows this much leakage, and you intend to use this if needed, then you should start with your mark higher up in the riser, say at 6".

*The following page is a summary for quick reference only and may not represent the latest standards.  For complete and up-to-date information, see each counties official website.