Rheem Tankless Water Heater Error Code P1: Meaning and Fix
Applies to: Rheem Eagle series tankless water heaters, indoor and outdoor (Use and Care manual AP22009, Service Error Code Chart); other Rheem tankless lines such as RTGH may use different codes.
Also shown as: P 1
Reading the tankless water heater display
A tankless water heater shows its fault as a number or letter code on the unit display or on the wired remote controller, and some models keep a short history of past codes. Write the code down exactly as shown before you reset the unit, and check the rating plate for the model number, because the same number can mean different things between series.
This page lists the fault codes this brand documents, with likely causes and a short repair path. Check the model label on your unit before using any chart.
What causes P1
- Faucet opened too little to start the unit
- Clogged aerator or inlet filter
- Partly closed water shut-off valve
How to fix it
If you smell gas, leave the building and call your gas utility from outside; do not touch switches or the unit. Switch the water heater off and let it cool before you touch any internal part, and call a licensed plumber or water heater technician if you are not sure.
The code meaning comes from the manufacturer document listed under Sources. The causes and steps below are general troubleshooting guidance, not the manufacturer's service procedure.
- Switch the water heater off and let it cool before you touch anything inside it. If you smell gas, leave the building and call your gas utility from outside.
- Open the hot tap further so more water flows.
- Check the aerator and the inlet filter for clogging.
- Confirm the water shut-off valves are fully open.
- If the code returns after these checks, call a licensed plumber or water heater technician and give them the code and the model number from the rating plate.
Questions
What does Rheem tankless error code P1 mean?
Code P1 on a Rheem Eagle tankless water heater means there is not enough water flow to operate the unit. Rheem's solution is to increase the water flow from the fixtures.
Can I reset the water heater myself?
Turning the unit off and back on, or unplugging it for about 30 seconds, clears some codes. If the same code comes back, the fault is still there and the unit will shut down again. Do not bypass a safety device to keep it running.
When should I call a technician?
Call a licensed plumber or water heater technician for anything involving gas, venting, the heat exchanger, a thermal fuse or the circuit board, or when the code keeps returning after the simple checks.
Other Rheem tankless water heater codes
Sources
Part numbers are OEM references; confirm fit by your model number before ordering. Meanings compiled from manufacturer and parts-retailer documentation; see sources below. Unplug the appliance before opening it.