Abstract: A pressurized chemical tank is connected to a water line through a restriction (e.g., a gas flow control valve). A vacuum-regulating check valve is for maintaining the vacuum pressure of the gas flowing between the tank and the restriction. A gas flow rate sensor is between the restriction and the water line. The sensor is constructed to be responsive to pressure in the gas line, and can be connected to a remote display and/or storage device. The sensor can also provide a feedback signal to a control system for controlling the flow rate.

Abstract: A meter is retrofitted for remote operation by replacing the lens with a replacement lens having a pickup transducer seated only in the replacement lens free of the meter casing.

Abstract: Apparatus for diverting backflow includes a housing having first and second pressure openings for receiving fluid signals representative of first and second pressures. The housing has a gas inlet and a gas outlet and is formed with a gas transmission passage for carrying gas from the gas inlet to the gas outlet. The housing has a vent passage communicating with the gas passage and the region outside the vent passage for carrying fluid from the gas passage to the region outside said housing. Valve structure movable in the housing is responsive to the difference in pressures at the first and second pressure openings for blocking fluid flow between the gas passage and the vent passage when the pressure difference is greater than a predetermined value and allowing fluid flow from the gas passage to the vent passage when the pressure difference is below a predetermined value.