sanitary manhole vacuum testing
One of the most common tests for infiltration/exfiltration in sanitary manholes is vacuum testing. The purpose of vacuum testing is to check for air leakage which upon a failed test, indicates that there are areas that might allow infiltration or exfiltration into or out of the sanitary manhole. This manhole leakage test is typically done after the manhole has been backfilled and compacted, though some feel it should be done prior to backfill so leakage troubleshooting is easier and more cost effective to conduct.
The inlet and outlet pipes in the manhole are typically plugged with pneumatic plugs. The test period amount of time is typically governed by the width and depth of the manhole, the wider and deeper the longer the test. Upon failure of a manhole pressure test, it can be very difficult to pinpoint the location of the leakage, especially after the backfill has been completed. If a manhole test fails it is common that the manhole will require repair by way of excavation around and application of a non-shrink grout to both the interior and exterior of the manhole.
If a manhole fails the test after initially failing and being repaired, it is often required to be replaced entirely by a new manhole. There are some that feel vacuum testing a backfilled manhole, when deep and when groundwater table exists, is ineffective because the exerted pressure may exceed the design limits of the flexible connectors, which could lead to a system failure.