Rheem Tankless Water Heater Code P1 [Fixed]

Rheem tankless water heater code P1 is the error indication of the too-low water flow in the system. In general, a tankless water heater will operate and activate the burner with a minimum flow rate of 0.4 gallons per minute. 

If you’re experiencing error code P1, it means that your water heater isn’t getting enough water flow to operate and maintain the set water temperature. 

It may occur due to any of the following reasons:

• Higher temperature setting
• Clogged water inlet filter
• Bad water flow sensor
• Blockage in the faucet aerators
• Or, plumbing crossover.

Don’t panic seeing the reasons. Just hold on tight with us till the end to deal with each of the reasons and to erase the Rheem tankless error code p1 effectively.

Possible Reasons & Solutions for Rheem Tankless Water Heater Code P1 [Quick Overview]

Before heading over to the details, let’s have a short glimpse at the quick table below, highlighting all the probable reasons and solutions for Rheem error code P1. 

What Does Rheem Tankless Water Heater Error Code P1 Mean?

Error code P1 on your Rheem tankless water heater mainly refers to the low water flow in the tankless system. 

Basically, an instantaneous or tankless water heater requires gas or electricity to provide hot water simultaneously. Overall,  they do not need a storage tank to store the hot water, but still, the tankless unit may run into issues with water pressure. 

Though the Rheem tankless water heater is efficient enough in its operation, it runs into technical issues occasionally. As such, it is normal you may experience a drop in water pressure that triggers the error code p1 on the remote display. 

You can check the current water flow rate of your tankless unit following the below procedures:

• First up, activate the maintenance mode of your Rheem tankless water heater.
• Push the up arrow button and select the diagnostic table.
• Now press the down arrow key until you get the 1Y table.
• While displaying the ‘1y’,  you will get the water flow reading of your tankless water heater in gallons per minute.
• Now, you can easily figure out where the reading is right according to the manufacturer’s instructions.

How To Fix Error Code P1 On Rheem Tankless Water Heater? [7 Easy Solutions]

As mentioned above, several factors can contribute to this issue, like higher temperature settings, clogged water filters, bad water flow sensors, cross lines in your home plumbing system, and so on.

Let’s track down each of the factors with effective corrective-solving methods:

1. The Unit Needs Resetting 

Whenever there is a water flow malfunction in my tankless water heater, I start the troubleshooting simplest fixes below.

 As per the manufacturer’s recommendation, you can reset the unit, and that would erase the error code P1 from your Rheem Tankless water heater. 

How To Fix:

Here is all to reset a Rheem tankless water heater:

Step #1: Start by turning off the power supply to your water heater. Turn off the power button on the remote control and unplug it from the power connection.

Step #2: Also turn off the water supply to your water heater by the shut-off valves. 

Step #3: Wait for about 10-20 seconds and let the heater reset at this stage.

Step #4: After that time, restore the power and water supply to your tankless unit. Check the nearest hot water fixture for your hot water heater. 

Expect that you will get hot water from there, and also, there will be no error code on the control display. 

If still yes, move ahead for further troubleshooting.

2. Incorrect Temperature Setting

The term may surprise you that the incorrect temperature setting was one of the big factors when I’m struggling with the bad water flow on my tankless water heater. 

Then I researched and found that, when you set the temperature too high at the remote control, you’re mixing too much cold water with too little hot water to keep the temperature at the shower head bearable. 

But all that results in low flow coming into the tankless water heater, or it may sometimes shut off. Tankless water heater unit requires a specific water flow rate to activate, and that’s the factor, setting the temperature correctly plays a big role. 

So, at this troubleshooting stage, head over to the remote control display and drop that water heater down to a lower temperature.

How To Fix: 

In general,  you can set the water temperature from 120°F (49°C) to 155°F (68°C) in the built-in remote controller of your Rheem Tankless water heater. You should keep it around 120 degrees- 130 degrees to get the hot water you ever need from your shower.

The 140 degrees can also be set, but it is applicable for commercial applications and not recommended for home showers. 140 Degrees will be too high for your home tankless water heater. 

Thus, it is better to set the temperature at 120 degrees or, at most, 130 degrees to create enough flow to keep the tankless unit on and to erase the error code P1 from the control display.

3. Blocked Water Inlet Filter

A water inlet filter is an essential element in a tankless water heater that is designed to remove scale-forming minerals and sediment from the water. By doing so, it protects the tankless unit from damage, corrosion, and diminished efficiency.

After long wear & tear and lack of maintenance, it is quite obvious to plug up the filter with the scale deposits. This results in a significant change in the water flow entering into the water heater. 

When the water flow rate decreases significantly, the tankless system triggers the error code P1 as a diagnostic alert. 

So, in this term, you will need to disassemble the water filter from your tankless unit connection and clean it thoroughly. Here is all for you to make the job simple:

How To Fix:

First off, make sure you’ve turned off the electric supply to your water heater. Also, turn off the gas and water supply from the shut-off valves. Now, try to loosen the water filter from the connection. Use pliers if needed. 

But all that you need is to place a little container or jar under the water filter while pulling it out, as water may come out. Anyway, after unscrewing the filter, figure out the overall condition of the filter.

Now, take a small brush or a crevice tool and remove the grime and particles that are caught up in the screen. Alternatively, you can use a Q-tip or toothpick to clean out the stubborn particles from the careen.

Finally, rinse the filter under running water and then dry it out using a soft cloth.

Once that’s all clean, reassemble the screen back into connection.

4. Malfunctioning Water Flow Sensor 

Unlike the water filter screen, the water flow sensor is another essential element of a tankless water heater that regulates the water flow of the unit. And then, it sends the signal to the computer board about the flow rate and initiates the heating process. 

In case the flow sensor malfunctions, it fails to regulate water flow, which triggers the error code P1 on the control display. At times, there would be no hot water in your Rheem tankless water heater. The higher possibility is the sensor is accumulated with dust and debris or broken itself. 

How To Fix:

First up, inspect the flow sensor for any blockages. But before that, turn off the electric and water supply to your water heater. Now, Remove four screws and disconnect the front cover. 

Locate the flow sensor from the lower part of the unit. It would be a short black elbow directly connected above the cold water connection. Remove the clamps holding the flow sensor in place and pull it out.

Now take a compressed air and blow out the dust and grime stuck in the sensor. When done, verify whether the sensor is in good working condition. First off, ensure that the wiring connections to the sensor are kept dry. 

Then, test the sensor connection to the PCB. In this instance, locate the connector S on the control board.

Take a voltage meter and measure the resistance reading S between the Red and Black. With the unit on and no water flow, it should give a reading of 11-17 DC volts. If so, turn on the water supply and measure 2-5 DC volts between the Brown and Black wire. 

If there is any malfunction in the resistance reading, replace the water flow sensor. Otherwise, you may need to replace the PCB.

5. Incorrect Water Pressure From Water Supply Lines 

In case of low water flow in your tankless water heater, the best chances are it is occurring from the main water supply line of your house. It may related to the water pressure regulator installed where the main water line enters the home. 

If it is set wrongly, it is obvious you’re encountering low water pressure in your faucets, including the water heater. 

Besides this, the plumbing system might be blocked by corrosion build-up, or the entire piping gets frozen due to a sudden decrease in temperature. All these factors are enough to restrict the water flow, leading to error code P1 on the remote display.

How To Fix:

Before assuming anything else, you can measure the water pressure of your house. All you need is a simple and inexpensive pressure gauge to check the water pressure with just a glance.

Now locate the home’s main water supply line from where the water enters the house. Now, screw the pressure gauge onto the faucet and Turn the faucet all the way.

Then, take the water-pressuring reading. It should give a reading of 40–50 psi as an ideal home water pressure. If not, you’ll need to adjust the pressure regulator of your house. 

To adjust that, locate the locknut on the adjustment screw of the regulator and loosen it with a wrench. Turn the screw until the water pressure reaches the desired level.

As with all these, inspect the plumbing pipes in your house for any blockage or frost. If so, remove the blockages or thaw the frozen pipes. Also, the pies should be narrow to restrict the water flow. If needed, Contact a professional to handle the best task for you.

6. Clogged Faucets Aerators Screen

Most of the time, the low water pressure issue of a tankless water heater may be restricted through the clogged aerator connected to the shower tap or shower kit.

After long wearing and training, it’s quite obvious that the aerators become clogged with mineral deposits, resulting in reducing the water flow below the minimum flow rate.

In this case, cleaning the stubborn clogs from the aerators is the only solution to get back the normal water flow.

How To Fix:

First up, you will need to disassemble your faucet and unthread the aerator to clean it thoroughly. If the aerator is stuck and hard to turn on, use a pair of pliers to loosen it. Avoid squeezing the pliers too much, as it could damage the aerator.

To clean the aerator parts:

• Take a screwdriver and pry out the mineral deposits or debris that may be stuck inside. 
• You can use a paper clip or a sewing needle to remove the dust effectively. 
• If needed, soak the aerator screen and other parts in a vinegar solution to dissolve mineral deposits. 
• After cleaning, reassemble the aerator parts back into their original order and screw them onto the spout.

Now head to the Rheem tankless water heater and check for error code P1. If it is still appearing, the issue is more likely related to the bad plumbing system of your house. Scroll down to learn more. 

7. Plumbing Crossover 

In case of malfunctioning water flow in your Rheem tankless water heater, cross connection to your home plumbing system is one of the big culprits to blame. 

Basically, the plumbing system of every house is divided into two main loops: hot & cold water supply. A plumbing crossover is such a situation when cold water gets into the hot water system or, conversely, hot gets into the cold system. Though the term may be confusing, it’s easy to find out the cross-connection of a home’s plumbing system. 

Here are simple steps to take:

Step #1: First up, turn off your Rheem tankless water heater. 

Step #2: Now turn on all hot water faucets. Wait for a few minutes until the water flow stops.

Step #3: Then, if you notice any water flowing, be sure you have a problem with the plumbing crossover.

Step #4: Now turn OFF all the faucets. And open only one faucet at a time to test. With turning on the faucet, switch to the cold water side. 

If you see water flowing, it means the probe lies here. Same as, test all other faucets as there has been more than one crossover. In your plumbing system.

How To Fix:

To be honest, the plumbing crossover is not so hard to repair. You just have to fix the cross-connection and make sure that the hot and cold water supply lines are connected to the appropriate hot and cold water assembly connections of the water ether. For that, we recommend calling a skilled professional technician to get this job done for you. 

Effective Ways To Boost Up The Water Pressure With Rheem Tankless Water Heater!

Well! After ensuring all the above troubleshooting steps, expect that we’ve successfully erased the error code P1 on your Rheem tankless water heater remote display. Now, we’re going to provide some effective tips to maintain the water flow of your water heater at all times to prevent such error codes from appearing in the future.

Here you go with some pro tips to boost up the water pressure of tankless water heaters, including all your home plumbing systems:

Tip #1: It is always recommended to check the water pressure on the incoming water line. If needed, adjust the pressure regulator to the required level.

Tip #2: If there is extreme water flow reduction in your plumbing system, the best chances are corrosion build up in the pipes lines or damage at all. 

For instance, replace the corroded pipes with new ones. Try to use copper pipes to prevent corrosion in the lines.

Tip #3: It is recommended to inspect your water heater for sediment deposits or scale build-up. Even it is crucial if you are living in the herd water area and your water heater always comes in contact with the minerals from the water. 

Tip #4: Sediment build-up blocks off the water lines, reducing water pressure. As a solution, you need to flush your tankless water heater at least once or twice a year to maintain the water flow and to run the water heater at its peak efficiency. 

Tip #5: One major factor to ensure that your tankless water heater is not too far from the hot water fixtures that could lower the water pressure. 

Tip #6: Last but not least, it is possible that you are using an undersized tankless system. When there is high hot water demand compared to the heater capacity, it is obvious there would be a major impact on the water flow. 

If your case is like that, consider upgrading your tankless system with a higher-capacity one.

FAQs:

In Closing

Well, that’s all here about the Rheem tankless water heater code P1. As earlier mentioned, the code is nothing but diagnostic information from the controller about the low water flow in the system. 

Whenever you encounter such an error code on the control display, figure out the actual reason for reducing the water flow rate. 

That’s the factor our above comprehensive guide will be enough to guide you to the right paths. Still, you’ll need to be highly concerned about the proper maintenance of your water heater to prevent this error code and any other error from your Rheem tankless systems. 

To get detailed information about maintenance, head over to our above-mentioned guide and ensure your water heater is running at its peak efficiency.