P1 Error Code With Rheem Tankless Water Heater

[costamesa]

Hello all,

I'm getting a P1 error code with my Rheem tankless water heater.
The issue seems to be isolated solely to the master shower, as all the other faucets, showers and fixtures activate the hot water.
In fact, if I first turn on one of the faucets in the bathroom and then run the shower, the water will stay on after turning off the faucet. Or vice versa, where if I turn on the shower and then the sink, then turn off the sink, the hot water keeps going.

I started noticing the issue about a couple of weeks ago.

Fixes I've attempted:

-Flushing the unit
-Cleaning the inlet filter on the unit

Background on the home:

-Built in 2015
-Water heater located on the first floor in the garage
-Shower having the issue located on the 3rd floor
-First time having the issue
-Unit is serviced yearly
-Previous issues with the water heater include code 11, which was solved in 2023

Does anyone have any ideas on what could be the cause for the issue and how to remedy it?

Thank you in advance!

 

[Twowaxhack]

follow my instructions exactly.

Turn the cold water off to the water heater and then go to a lavatory faucet and turn on the hot water only. The flow of water should stop after the initial pressure is relieved.

If the water continues to flow, that’s a problem. It should stop.

Let me know.

 

[costamesa]

follow my instructions exactly.

Turn the cold water off to the water heater and then go to a lavatory faucet and turn on the hot water only. The flow of water should stop after the initial pressure is relieved.

If the water continues to flow, that’s a problem. It should stop.

Let me know.

Thank you for the reply.
I will give this a try when I get home from work.

How do I stop the cold water on the heater?

 

[Twowaxhack]

Thank you for the reply.
I will give this a try when I get home from work.

How do I stop the cold water on the heater?

Should be a valve close by that will shut the cold water off to the water heater.

 

[costamesa]

Should be a valve close by that will shut the cold water off to the water heater.

Okay, thank you!