Water Temperature too Hot
Temperature dial set too high
There are restrictions in the
Inlet water temperature is too
Water Temperature fluctuates
Cold mix, heater deactivates
Fluctuating water pressure
Changing flow rate.
Water supply connected to the
outlet of the unit.
Turn the temperature knob located on the front of the water heater counterclockwise for cooler
Obstructions in the water path can restrict the flow of water through the heater causing
overheating. Verify the heater's inlet filter screen, faucet aerators, showerheads and whole
house filters are clear of debris. Verify proper flow on the inlet side of the heater with the hot
water pipe disconnected. Opening cold water isolation valve fully may be necessary. Maximum
flow rates for each unit are as follows. WH17 - 2.3gpm, WH27 - 3.5gpm.
Verify the heater is being feed with cold water only. This water heater is not designed for
preheated water or recirculation applications. Increase flow rate where ever possible.
Replacing low flow showerheads and aerators with higher flowing (GPM) ones may be
If inlet water temperature is over 70°F, water may be very hot out of the tap. This requires a lot
of cold water to be added in order to get a usable hot water temperature. The addition of too
much cold water will overpower hot water demand from the water heater. This slows the flow
within the water heater, decreasing it below the activation point, which shuts off the heater.
The end result is nothing but cold water coming out of the outlet. Increase the flow rate by
cleaning or replacing fixtures and lower the setting on the temperature adjustment knob.
If the water pressure in the home is erratic and the water flow is not consistent while a tap is
opened, then the temperature of hot water will fluctuate. The minimum water pressure for the
home should be 30psi or greater. For people on well systems the minimum pressure range is
30-50psi. The use of a pressure reducing/regulating valve is an effective way to maintain
constant water pressure to the water heater. Watts brand 25AUB- ¾" or N35B-¾" pressure
reducing/regulating valves or equivalent is suggested.
Major changes in flow rate can adversely affect the output water temperature of the heater.
Increases from one major fixture running to multiple fixtures running at one time can cause the
temperature to fluctuate. Stay within the heater's specifications. See Fig. 11.
Troubleshooting | 21
6 720 646 951 (2015/04)