The Ontario Building Code | Relief Valves

7.6.1.12. Relief Valves

(1) Every pressure vessel that is part of a plumbing system or connected to a plumbing systemshall be equipped with a pressure relief valve designed to open when the water pressure in the tank reaches the rated working pressure of the tank, and so located that the pressure in the tank shall not exceed 1 100 kPa or one-half the maximum test pressure sustained by the tank, whichever is the lesser.

(2) Every hot water tank of a storage-type service water heater shall be equipped with a temperature relief valve with a temperature sensing element,

(a) located within the top 150 mm of the tank, and

(b) designed to open and discharge sufficient water from the tank to keep the temperature of the water in the tank from exceeding 99°C under all operating conditions.

(3) A pressure relief valve and temperature relief valve may be combined where Sentences (1) and (2) are complied with.

(4) Every indirect service water heatershall be equipped with,

(a) a pressure relief valve, and

(b) a temperature relief valve on every storage tank that forms part of the system.

(5) Every pipe that conveys water from a temperature relief, pressure relief, or a combined temperature and pressure relief valve shall,

(a) be of a sizeat least equal to the size of the outlet of the valve,

(b) be rigid, slope downward from the valve, and,

(i) terminate with an indirect connection above a floor drain, sump or other safe location, with an air break of not more than 300 mm, or

(ii) terminate at a distance not less than 150 mm and not more than 300 mm from a floor and discharge vertically down,

(c) have no thread at its outlet, and

(d) be capable of operating at a temperature of not less than 99°C.

(6) The temperature relief valve required in Clause (4)(b) shall,

(a) have a temperature sensing element located within the top 150 mm of the tank, and

(b) be designed to open and discharge sufficient water to keep the temperature of the water in the tank from exceeding 99°C under all operating conditions.

(7) No shut-off valve shall be installed on the pipe between any tank and the relief valves or on the discharge lines from such relief valves.