Exfiltration test. All sewers shall satisfy requirements
of a final exfiltration test before they will be approved and sewage
flow accepted from them by the County. This test consists of filling
the pipe with water to provide a head of at least five feet above
the top of the pipe or five feet above groundwater, whichever is higher
at the highest point of the pipeline under test, and then measuring
the loss of water from the line by the amount which must be added
to maintain the original level. In this test, the line must remain
filled with water for at least 24 hours prior to the taking of measurements.
Exfiltration shall be measured by the drop of water level in a standpipe
with a closed bottom end, or in one of the sewer manholes available
for convenient measuring. When a standpipe and plug arrangement is
used in the upper manhole of a line under test, there must be some
positive method of releasing entrapped air in the sewer prior to taking
measurements. The test length intervals for either type of test shall
be as ordered or approved but in no event shall they exceed 1,000
feet. In the case of sewers laid on steep grades, the length of line
to be tested by exfiltration at any time may be limited by the maximum
allowable internal pressure on the pipe and joints at the lower end
of the line. The test period, wherein the measurements are taken,
shall not be less than two hours in either type of test. The total
leakage of any section tested shall not exceed the rate of 100 gallons
per mile of pipe per 24 hours per inch of nominal pipe diameter. For
purposes of determining the maximum allowable leakage, manholes shall
be considered as section of forty-eight-inch diameter pipe, five feet
long. The equivalent leakage allowance shall be 4.5 gallons per manhole
per 24 hours, for forty-eight-inch diameter manholes. If leakage exceeds
the specified amount, the necessary repairs or replacements required
shall be made to permanently reduce the leakage to within the specified
limit, and the test shall be repeated until the leakage requirement
is met.