HOT
COLD
ON!
Cold Drain
Valve
Cold
Isolation
Valve
PRV Lever
Hot Isolation
Valve
Hot Drain
Valve
HOT
P
RV
COLD
Figure 48: Piping Diagram
Rinnai Tankless Water Heater Installation and Operation Manual
57
6.3 Draining the Water
Heater
To avoid burns, wait until the equipment cools
down before draining the water. The water in the
appliance will remain hot after it is turned off.
WARNING
If the water heater is not going to be used
during a period of possible freezing weather, it
is recommended that the water inside the water
heater be drained.
To manually drain the water:
1. Shut off cold water supply and gas supply.
2. Turn off the temperature controller.
3. Disconnect the power to the water heater.
4. Close the hot and cold isolation valves.
5. Open the pressure relief valve (PRV) lever.
6. Open the hot and cold drain valves and loosen
the inlet water filter.
To resume normal operation:
1. Confirm that the gas supply is turned off, all
taps are closed and PRV lever is closed.
2. Close the hot and cold drain valves.
3. Open the cold and hot water isolation valves.
4. Connect power to the water heater and tighten
the inlet water filter.
5. Open a tap and confirm that water flows, and
then close.
6. After confirming that the temperature controller
is off, turn on the gas supply.
7. Turn on the temperature controller.
Running a low volume of water through the
water heater to prevent freezing:
If the temperature exceeds the ability of the water
heater to freeze protect itself, or if power is lost,
the following steps may prevent the water heater
and external piping from freezing. Units connected
with EZConnect™ (2-unit link) should be drained
to prevent freezing if not in use.
1. Turn the water heater off and close the gas
supply valve.
2. Turn on a hot water tap to flow
water about 0.1 gal/min (0.4
L/min) or where the stream is
about 0.2 in. (5 mm) thick.
When the water heater or external piping has
frozen:
1. DO NOT operate the water heater if the unit or
the external piping is frozen.
2. Close the gas and water valves and turn off
the power.
3. Wait until the water thaws. Check by opening
the water supply valve.
4. Check the water heater and the piping for
leaks.
