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Rinnai Tankless Water Heater Installation and Operation Manual 52
4.8 Install Pressure Relief Valve
Water discharged from the pressure relief valve could cause severe burns
instantly or death from scalds.
4.8.1 Guidelines
An approved pressure relief valve is required
by the American National Standard (ANSI
Z21.10.3) for all water heating systems and shall
be accessible for servicing. When connecting a
pressure relief valve, follow the guidelines below:
• The pressure relief valve must comply with
the standard for Relief Valves and Auto-
matic Gas Shuto Devices for Hot Water
Supply Systems ANSI Z21.22 and /or the
standard Temperature, Pressure, Tem-
perature and Pressure Relief Valves and
Vacuum Relief Valves, CAN1-4.4.
• The pressure relief valve must be rated
up to 150 psi and to at least the maximum
Btu/hr of the appliance.
• The discharge from the pressure relief
valve should be piped to the ground or into
a drain system per local codes.
• The pressure relief valve must be man-
ually operated once a year to check for
correct operation.
• The discharge line from the pressure relief
valve should pitch downward and termi-
nate 6 in. (152 mm) above drains where
discharge will be clearly visible.
• The discharge end of the line shall be plain
(unthreaded) and a minimum of 3/4 in.
nominal pipe diameter. The discharge line
material must be suitable for water at least
180° Fahrenheit.
• The pressure relief valve is assembled to
the pressure relief valve adapter as illus-
trated on the next page. DO NOT place
any other valve or shut o device between
the pressure relief valve and the water
heater.
• If a pressure relief valve discharges peri-
odically, this may be due to thermal expan-
sion in a closed water supply system. Con-
tact the water supplier or local plumbing
inspector on how to correct this situation.
Do not plug the pressure relief valve.
• The American National Standard (ANSI
Z21.10.3) does not require a combination
temperature and pressure relief valve for
this appliance. However, local codes may
require a combination temperature and
pressure relief valve.
• Protect pressure relief valve and pressure
relief valve discharge line from freezing.
Do not plug or restrict ow of the pressure
relief valve.
• DO NOT plumb the pressure relief valve
with the condensate drain; both must be
plumbed independently to drain.
• DO NOT plug the pressure relief valve and
do not install any reducing ttings or other
restrictions in the relief line. The pressure
relief line should allow for complete drain-
age of the valve and the line.
• DO NOT place any other valve or shuto
device between the pressure relief valve
and the water heater.
WARNING
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