Why Is My Rheem Water Heater Status Light Blinking Blue?

Rheem water heater status light is blinking blue due to a clogged exhaust vent, a defective pressure switch, or a faulty flammable vapor sensor. 

Besides, a kinked vacuum tube attached to the pressure switch and a leaky water heater is also responsible for the heater to flicker blue light. 

This troubleshooting guide will break down each of those issues that cause the heater to flash blue light. So, stay with us till the end.

Read Also: Rheem Water Heater Blinking Red Light 

Table of Contents

What Does Blue Flashing Light On Water Heater Mean?

The blinking blue light on Rheem water heater indicates something is not working correctly. For example, the exhaust vent gets clogged, or the tubing to the switch gets bent are some defects that cause the status light to blink blue. 

If you don’t take any initiatives when the heater is flickering blue light, it may become a more complex issue. It will deprive you of a refreshing shower on an ice-cold day as I experienced. 

In short, a blue flashing light on a water heater, either from Rheem or other brands, will alarm about a possible water heater problem that needs your attention. 

Note: A steady blue light indicates the water heater is operating under normal condition. 

Why Is My Rheem Water Heater Status Light Blinking Blue?

This chapter will disclose every reason that causes your Rheem water heater to blink blue light. 

01. A Block Exhaust Vent

Rheem hot water heater status light blinking blue! Then, my first suspicion goes to the exhaust vent. If it gets blocked by dirt, debris, or spillage, your water heater will gleam the blue light. Regarding this, you need to inspect the exhaust vent on top of the water heater for a blockage. 

How To Fix: 

To check the exhaust vent, start the heater and run it for several minutes. It is so that the upward draft can be established and gasses can easily go through the vent. 

Next, light and extinguish a match. Hold it near the base of the vent pipe. You should see the smoke being drawn into the flue. It indicates the vent is pulling air inside and venting properly.

Inspecting the exhaust vent for blockage
*Inspecting the exhaust vent for blockage

If the exhaust vent is blocked, the smoke will never go into the vent pipe. 

In the case of exhaust vent blockage, turn your water heater off right off the bat and call a certified plumber. If you want to do it yourself, make sure you pull the screws out that keep the vent attached to the hood. 

Remove the exhaust vent and check it for blockage. Also, don’t forget to inspect the vent to see whether it changes in diameter or not. 

02. Tubing to the Switch May Get Kinked

Every water heater has a pressure switch that you can find on top of the water heater. To access the pressure switch, you must remove the combustion chamber panel. 

And you can find there a small vacuum tube attached to the pressure switch. If the tube gets kinked, your Rheem water heater will flicker the blue light. 

How To Fix: 

The solution to this issue is simple. It requires no plumbing knowledge to fix. Just inspect the tubing to the pressure switch. It should be straight.

Vacuum tube to the pressure switch
*Vacuum tube to the pressure switch should be straight*

Otherwise, you just need to straighten the kinked vacuum tube.  If the vacuum tube gets cracked, replace it with a new one.

03. A Defective Pressure Switch

Rheem water heater flashing blue light 3 times! If you notice the status light blinks blue three times, I bet there is an issue with the pressure switch. 

Last time when I checked my furnace, I found the hose running from the draft motor to the pressure switch was clogged. And that was the culprit that caused the pressure switch to fail. 

Besides, high voltage can also be the caveat that will trip or blow out the pressure switch of your Rheem furnace. 

Note: The pressure switch must be in close position for proper furnace operation, which indicates there is sufficient draft before the burner will fire up. 

How To Fix: 

Begin with inspecting the pressure switch electrically. Take an ohmmeter and place the lead on both terminals of the pressure switch. 

The reading should be between 0 to 0.1. Anything above this will indicate that the switch gets faulty. I recommend you check the this tutorial if you don’t know how to test the pressure switch. 

If you get the negative results from the test, it’s time to replace the pressure switch. Follow the below steps to change the Rheem furnace pressure switch.

First off, turn off the power to your furnace. 

Secondly, remove the upper access panel from your Rheem water heater.

Removed the access panel
*Removed the access panel*

Then, ensure you remove the vacuum tube from the old pressure switch. Also, don’t forget to disconnect the wires.

Disconnecting the vacuum tube and the wires
*Disconnecting the vacuum tube and the wires*

Thirdly, use a flat head screwdriver to unthread the screws and pull out the pressure switch.

Unthreading the screws using a flat head screwdriver
*Unthreading the screws using a flat head screwdriver*

And finally, install the new pressure switch in the bracket by positioning it under the frame and threading the screws to secure the switch in its place. 

Afterward, connect the vacuum tube and the wires to the appropriate terminals. And end the installation workflow by bringing the access panel back into its place.  

04. A Leak In The Water Heater

Rheem water heater flashing blue light 6 times! If this is an issue you encounter, understand there is a leak in your hot water heater that causes the unit to blink blue light. 

Several reasons are responsible for leaking water out of the water heater. They are: 

  • A corroded T&P valve
  • Internal tank gets damaged
  • Excessive water pressure

How To Fix: 

The first thing I recommend you do is to find the source of the water leak. If the water is leaking due to a corroded T&P valve, you need to replace it. Regarding this, you can find this tutorial helpful to replace the valve: 

Note: There are hundreds of reasons behind a leaky water heater that make me feel like creating a separate guide on the subject. Next Sunday, I will publish an in-depth guide on Rheem Water Heater Leaking. Till then, stay in tune with us. 

Announcement: Hey, the guide on Rheem Water Heater Leaking is now live. You can check it here.

05. Faulty Flammable Vapor Sensor

If your water heater is blinking the blue light 7 times, understand there is a problem with a flammable vapor sensor. As I dug into the manual, I discovered the 7 flashes indicate the flammable vapor sensor is in lockout mode. 

How To Fix: 

Resetting the flammable vapor sensor is an easy fix to the issue. I suggest you check the following tutorial to learn how to reset the flammable vapor sensor on your Rheem water heater. 

06. Flammable Vapor Sensor Goes Out of Specification

Your Rheem water heater status light will also be blinking blue if the flammable vapor sensor goes out of specifications. In this case, the status light will flicker blue light 8 times. 

How To Fix: 

Pull the flammable vapor sensor from the base of the water heater and detach the wires. Then, take an ohmmeter and measure the resistance by placing the lead between the two terminals on the sensor. The reading should be 7000 to 25, 000 Ohms. Otherwise, you should replace the flammable vapor sensor. 


Blinking blue light on the Rheem water heater indicates something is going wrong with the heater. Typically, a blocked exhaust vent, a vacuum tube to the pressure switch gets clogged, or a faulty flammable sensor are some culprits that cause the status light to blink blue. 

Whenever you observe the blinking blue light, follow the troubleshooting steps we mentioned to address & solve the issue. Otherwise, the small problem will turn into a big one and bring significant damage to your water heater. 

Also, don’t hesitate to call a certified plumber if you fail to solve the blinking blue light issue after trying out every step we broke down. 

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