(See Note A-7.6.1.7.)
(1)
Every pressure vessel that is part of a plumbing system or connected to a plumbing system shall 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)
The 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)
Indirect service water heaters shall 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)
Pipes that convey water from a temperature-relief, pressure-relief, or a combined temperature- and pressure-relief valve shall
(a)
be of a nominal pipe size at least equal to the NPS of the outlet of the valve,
(b)
be rigid, slope downward from the valve, and terminate with an indirect connection above a floor drain, sump, or other safe location, with an air break of not more than 300 mm,
(c)
have no thread at its outlet, and
(d)
be capable of operating at a temperature of not less than 99°C.. (See Note A-7.6.1.7.(5))
(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.