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Tests have shown that up to 45 gallons of water per minute can enter a collections system through a single standard 24-inch-diameter manhole cover with two 1-inch-diameter pick holes.
Inflow is the first “I” in I&I, but it regularly takes a back seat to infiltration.
The inflow of stormwater into collections systems is often the result of illegal or improper connections, but excess flow entering the system through manhole covers can also pose significant threats. It’s a problem that plagues communities throughout the U.S.
When rainfall or snowmelt cause unwanted water to enter the collections system through manhole covers, the amount of actual flow...
