 The housing is vented to the outside to allow air to displace the water as the water level in the unit rises and falls.The amount of torque that can be absorbed is defined by the equation T=kN2D5 where T = torque, N = RPM, D = the diameter of the rotor and k = a constant dependent on the size and shape and angle of the rotor/stator pockets.Systems that require the torque of the system under test to be measured typically use a strain gauge mounted on a torque arm that is attached to the housing perpendicular to the input shaft.