Abstract: A test apparatus for measuring the rate (volume as a function of time) of surface water runoff infiltration inflow into a manhole that includes a portable liquid impervious barrier that can retain a predetermined volume of water and sized to extend and encompass a manhole cover and the manhole supporting structure, the barrier including a waterproof gasket along its base, and a liquid level measuring device positioned inside the barrier that can determine first and second liquid levels within the barrier as a function of time. When the liquid impervious barrier is filled with water, the device is actuated when a particular water level is reached. After liquid has infiltrated into the manhole structure, the level will drop in the barrier and when a predetermined low level is reached, the measuring device will compute the time lapsed and the volume that has left the barrier.

Abstract: A liquid impervious closure for a sewer system manhole opening having a single bi-directional pneumatic breather valve that allows for pneumatic pressure equalization on either side of said closure. The closure is comprised of a pan-shaped barrier and the breather valve mounted there through, said valve having a housing of threadably joined casings enclosing a single moveable sealing plug that engages a gasket to prevent liquid flow in one direction while permitting air flow in either direction.

Abstract: A manhole closure for diverting liquid away from a sewer system that is readily installable in a conventional manhole opening beneath a manhole cover, the device including two-way pressure relief valves to compensate for increased or decreased system pressure (relative to atmospheric) within the manhole system while preventing excessive amounts of rainwater and the like, chemical spills or other undesirable pollutants from entering the sanitary sewer system. The two-way valve system includes upper and lower counterweighted flapper valves which sealably cover passages within the closure housing. A valve supporting plate is enclosed in a cylindrical housing and includes upper and lower strainers, the housing being readily mountable in a conventional manhole opening by a rigid supporting rim affixed to the housing. The device will divert liquid flow away from a sanitary sewerage system while preventing over or under gas pressure conditions from developing within the system.