Rheem Tankless Water Heater Code P1 indicates too low water flow that prevents the unit from kicking on. Typically, the water flow gets too low when the cold water inlet filter gets filthy by minerals or deposits.
To clear the error code P1, you must clean the cold water inlet filter. If the inlet filter looks so fragile, don’t hesitate to replace the filter. And this guide will help you in cleaning or replacing the cold water inlet filter. So, let’s dive in.
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How To Clear Rheem Tankless Water Heater Code P1?
The tankless unit will throw the error code P1 when the water flow is low. To fire the unit, you should clean the cold water inlet filter to gain a minimum flow rate of 0.4 GPM.
Here is the step-by-step procedure to clean or replace the cold water inlet filter:
1. Turn off the water heater by pressing the power button on the remote control and disconnect the unit from the electric power supply.
2. Turn off the water supply to the water heater. You should shut off both the cold and hot water supply to the unit. Regarding this, locate the cold water supply valve and the hot water supply valve at the bottom of the unit and turn them off. Both valves should be perpendicular to the pipe, which indicates the water is turned off.
3. Drain the water heater. This step is optional as you can remove the cold water inlet filter without draining the unit. However, I highly recommend you drain the tankless unit before removing the filter. You can drain the water heater by using the pressure relief valve or the isolation valve on the cold water side.
4. Now, it’s time to remove the cold water inlet filter. Use a channel lock or your hand to unscrew the cold water inlet filter. As you are going to remove the filter, ensure you place a plastic bucket under the filter to catch the drippings.
See how the cold water inlet filter of this unit is dirty:
Take the inlet filter under running water and clean it. You can use a toothpick to remove the gunk or deposits from the filter.
Rinse the filter evenly.
5. Once you clean the filter, install it to its place. If the cold water inlet filter gets damaged, get a new one and reinstall the filter. Then, secure the filter by turning it to the right.
Lastly, turn on both the cold water and the hot water supply valves and ensure no water leaking from them. Restore the power to the unit and turn on your water heater by pressing the power button on the remote control.
P1 error code on Rheem Tankless Water Heater indicates low water flow rate. It occurs when the cold water inlet filter gets restricted. To resolve this issue, check the inlet filter and clean it. Fortunately, I already described how to clean the cold water inlet filter in five simple ways. Follow them and clean the filter to reset the error code P1.
Sohel Rana is an expert writer (Of course, the owner and founder of this blog) on plumbing, HVAC, and appliance repair & troubleshooting. Since 2020, he has written on these specific topics, though his writing journey began in 2018.