How to Replace a Water Heater Pilot Light: A Step-by-Step Installation Guide

No hot water due to an ignition failure?

This comprehensive guide will teach you how to replace a water heater pilot light and properly ignite a gas burner. We’ll start with the basics, explaining the function and importance of the pilot light in your water heater system. You’ll gain a clear understanding of how the pilot light works, why it might fail, and the common signs of ignition issues.

Additionally, we’ll provide step-by-step instructions on what to do when the pilot flame goes out or is not lighting helping you troubleshoot and resolve the problem efficiently.

Whether you’re a DIY enthusiast or simply looking to save on repair costs, this article offers all the information you need to restore your hot water and maintain your water heater effectively.

How to Replace a Water Heater Pilot Light: Things to Consider

What Is a Water Heater Pilot Light and How Does It Work?

A water heater pilot light is a small, continuous flame that serves to ignite the gas burner inside the water heater. This pilot flame remains lit at all times, ready to ignite the burner when the thermostat signals the need for heating. It’s an essential component for gas-powered water heaters, providing a reliable ignition source even in the event of a power outage.

The gas burner assembly typically includes the pilot burner, thermocouple, burner tube, main burner, and gas valve, all working together to light the burner and produce hot water. The gas valve controls the flow of gas to the pilot light and burner, ensuring the system operates efficiently.

One of the main advantages of a water heater pilot light is its independence from the electrical system. Since it’s always burning, it can ignite the burner even if there’s a power outage, making it a reliable option during electrical disruptions.

However, the constant burning of the pilot flame can lead to energy waste when the water heater is not actively in use. Additionally, there’s a safety concern with the potential ignition of flammable vapors—such as those from gasoline or paint—if the unit is left on in an area with these vapors.

To address the vapor hazard, many modern water heaters are equipped with a Flammable Vapor Ignition Resistant (FVIR) system. This system automatically shuts off the gas supply to both the pilot and burner, preventing the ignition of any surrounding flammable vapors.

In recent years, many gas appliances have shifted to electric ignition systems. These use high-voltage electrical arcs or hot surfaces to ignite the gas, eliminating the need for a continuously burning pilot light and improving energy efficiency.

How to Light the Pilot: Step-by-Step Instructions

Based on the different gas control valve manufacturers, lightning instructions are slightly different.

The most common lightning system is a piezoelectric igniter system, consisted of the igniter button, an electrode, and a wire. The pilot is ignited by an electric spark generated when the igniter button is depressed. The spark gap distance measured from the electrode tip to a pilot is factory set to 0.125 inches and must be maintained for successful lighting.

How to check the piezo igniter?

Check if the spark is present when the button is depressed fully. Use a sight glass window while viewing the pilot assembly to see the action if it is present.

Here is the step-by-step guide on lighting a hot water heater if the piezoelectric igniter ignites the pilot flame.

• Remove the outer door panel.
• Turn the temperature control to its lowest setting.
• Put the gas knob to the OFF position.
• Wait for a few minutes to clear out any accumulated gas.
• Turn the gas control knob to the pilot position (Robertshaw gas valve).
• Depress and hold down the pilot set button or gas control knob to let the gas flow to the pilot burner only.
• Manually ignite this pilot gas using the piezo igniter button by depressing the igniter until you hear a loud click.
• Continue to hold the button for up to one minute after the pilot light is lit to let the flame heat the thermocouple and generate sufficient voltage to the gas valve.
• Release the knob, and it should pop back up.
• Turn the gas control knob to the ON position.
• Set the thermostat to the desired temperature.

Also, check these instructions and the article about different types of gas valves, it can help you understand the lighting process better.

What Happens if the Water Heater Pilot Light Goes Out?

If the knob does not pop up when released or the pilot doesn’t stay lit after several tries, turn the gas control knob to the OFF position, or the main gas valve, and contact the service technician.

The air may be present in the gas line and could prevent the pilot from lightning on initial start-up. The gas line should be purged of air by a qualified person.

The water heater is designed to automatically shut off if the pilot light is extinguished for any reason. Thanks to the safety devices, the gas will not keep coming out of the pilot light tube.

The thermocouple is one of these safety elements that prevents the gas from coming out. While sitting in the pilot flame, it can determine if the flame is present or not. The thermocouple will send the electrical signal to the gas valve to shut off the gas supply to the pilot and main burner if the flame is absent. If the light is extinguished, it can take up to 3 min for the thermocouple to cool sufficiently and close the safety valve.

To re-light the water heater pilot light, you have to push the button to open the gas valve manually. Then you light the pilot light and wait for up to 60 sec for the thermocouple to heat up. Once it is hot, the thermocouple will generate electricity to hold the valve in an open position. Then you can release the button.

The normal voltage for a properly working thermocouple is between 20 and 30 mV, and when installing, make the base flush with the base of the pilot bracket.

Common Pilot Light Problems in Gas Water Heaters

Pilot issues are among the most common problems with gas water heaters. Here are the three main signs of the problem:

• No Hot Water
• No Flame
• Error Message or Blinking Light on the Gas Valve

Before we dive into replacing a pilot light, let’s first explore the reasons it may need replacing.

Reasons for a Malfunctioning Pilot Light

• Malfunctioning, Damaged, or Clogged Pilot
• Damaged or Clogged Pilot Orifice
• Malfunctioning or Damaged Thermocouple
• Soot Build-Up and Carbon Deposits

Of course, there are other reasons for the pilot failure, and several are covered in the article – pilot light goes out due to improper venting.

How to Replace a Water Heater Pilot Light and Tube Assembly

A water heater pilot light is one of the main culprits of “no hot water” problems and when a gas water heater is not heating.

Note that this part cannot be fixed if broken, so the best is to get familiar with the instructions on how to replace a water heater pilot light and change it yourself (but only if you are comfortable).

• Turn off the gas supply to the water heater by putting the knob in the “OFF” position.
• Set the temperature dial on the gas control valve and thermostat to the lowest setting.
• Remove the door panel.
• Remove the screws that are securing the manifold assembly to the combustion chamber.
• Disconnect the thermocouple, the tube, igniter wire, thermal switch, and manifold tube and push them slightly down to release them.
• Remove the manifold assembly and release the burner.
• Remove the pilot tube from the pilot bracket.
• Using the old pilot tube assembly as a guide, bend the new tube and thermocouple to match the old ones.
• Route the new pilot tube, thermocouple, and igniter wire through the manifold assembly.
• Bring everything back in reverse order, secure the screws, re-install burner assembly and connect the feedline.
• After the new assembly is installed, check for any gas leaks using soapy water on the connections. If you see bubbles, tighten the connections.
• Follow the manufacturer’s instructions for reigniting the pilot light. This usually involves turning the gas control valve to “Pilot,” pressing the button to allow gas flow, and using an igniter to spark the pilot.
• Once the pilot is lit, turn the gas control valve to “On” and set the thermostat to your desired temperature. Check to ensure the water heater is functioning properly.

Tip: Regularly inspecting the pilot light visually is essential for spotting defects, damage, or build-up. Catching these issues early can prevent cold showers or more serious problems down the line.