15
T&P Relief Valve
Drain Line
Manual Relief Lever
T&P Relief Valve Insulation
FIGURE 25.
TEMPERATURE-PRESSURE RELIEF VALVE
This heater is provided with a properly certified combination
temperature - pressure relief valve by the manufacturer.
The valve is certi
fi
ed by a nationally recognized testing laboratory
that maintains periodic inspection of production of listed equipment
of materials as meeting the requirements for Relief Valves and
Automatic Gas Shut-off Devices for Hot Water Supply Systems,
ANSI Z21.22 • CSA 4.4.
If replaced, the valve must meet the requirements of local codes, but
not less than a combination temperature and pressure relief valve
certi
fi
ed as indicated in the above paragraph.
The valve must be marked with a maximum set pressure not to
exceed the marked hydrostatic working pressure of the water heater
(150 psi = 1,035 kPa) and a discharge capacity not less than the
water heater input rate as shown on the model rating plate.
For safe operation of the water heater, the relief valve must not be
removed from its designated opening nor plugged.
The temperature-pressure relief valve must be installed directly into
the
fi
tting of the water heater designed for the relief valve. Position
the valve downward and provide tubing so that any discharge will
exit only at any distance below the structural
fl
oor and external to
the building. In cold climates, it is recommended that the discharge
pipe be terminated at an adequate drain inside the building. Be
certain that no contact is made with any live electrical part. The
discharge opening must not be blocked or reduced in size under
any circumstances. Excessive length, over 30 feet (9.14 m), or
use of more than four elbows can cause restriction and reduce the
discharge capacity of the valve, see Figure 26.
No valve or other obstruction is to be placed between the relief valve
and the tank. Do not connect tubing directly to discharge drain
unless a 6 inch (15 cm) air gap is provided. To prevent bodily injury,
hazard to life, or property damage, the relief valve must be allowed to
discharge water in quantities should circumstances demand. If the
discharge pipe is not connected to a drain or other suitable means,
the water
fl
ow may cause property damage.
The Discharge Pipe:
• Shall not be smaller in size than the outlet pipe size of the valve, or
have any reducing couplings or other restrictions.
• Shall not be plugged or blocked.
• Shall be of material listed for hot water distribution.
• Shall be installed so as to allow complete drainage of both the
temperature-pressure relief valve, and the discharge pipe.
• Shall exit only at any distance below the structural
fl
oor and
external to the building. In cold climates, it is recommended that
the discharge pipe be terminated at an adequate drain inside the
building.
• Shall not have any valve between the relief valve and tank.
• Temperature-pressure relief valve
must comply with ANSI Z21.22-
CSA 4.4 and ASME code.
• Properly sized temperature-relief
valve must be installed in opening
provided.
• Can result in overheating and
excessive tank pressure.
• Can cause serious injury or
death.
The temperature-pressure relief valve must be manually operated
at least once a year. Caution should be taken to ensure that (1) no
one is in front of or around the outlet of the temperature-pressure
relief valve discharge line, and (2) the water manually discharged
will not cause any bodily injury or property damage because the
water may be extremely hot.
If after manually operating the valve, it fails to completely reset and
continues to release water, immediately close the cold water inlet
to the water heater, follow the draining instructions, and replace the
temperature-pressure relief valve with a new one.
FIGURE 26.
