How to Safely Light a Rheem Hot Water Heater

What safety checks should you do before lighting?

Natural gas and propane are naturally odorless fuels, so utility companies add mercaptan, a chemical that smells like rotten eggs. Before touching any dials on your Rheem water heater, use your nose. Propane is heavier than air and settles near the floorboards, while natural gas rises but can linger in enclosed alcoves. If you smell gas anywhere around the tank, do not attempt to light the pilot. A spark or open flame in a room with pooled gas can cause a flash fire.

Run through this quick safety checklist before touching the unit:

• Sniff the air at eye level and directly along the floorboards around the base of the tank.
• Move any paint cans, solvent rags, cleaning chemicals, or gasoline containers at least 3 feet away from the heater.
• If the water heater was recently running or you just attempted to light it, switch the control knob to OFF and wait a full 10 minutes so lingering fumes can draft up the exhaust vent.
• Locate the main gas shutoff valve on the supply pipe so you know how to stop the fuel flow quickly if needed.
• If you smell a strong gas odor, leave the home immediately, avoid flipping electrical light switches, and call your gas utility or fire department from outside.

How do you light a modern Rheem water heater?

Modern Rheem gas water heaters use a sealed combustion chamber to prevent household vapors from reaching the burner. These models feature a small view window (sight glass) on the lower access door and a push-button sparker (piezo igniter) on the thermostat dial box (gas control valve). You do not need matches or an open lighter for these models.

Follow these steps to ignite a modern Rheem pilot flame:

1. Turn the temperature dial on the thermostat dial box down to its lowest setting, labeled "LOW" or "VACATION". This keeps the main burner from roaring on abruptly when the pilot catches.
2. Turn the gas control knob to OFF. If the unit was already set to PILOT or ON, wait 10 full minutes on OFF to let any unburned gas escape up the chimney flue.
3. Rotate the gas control knob to PILOT and align the mark with the indicator line on the housing.
4. Press and hold the control knob down completely. Holding this knob down manually feeds a small stream of gas to the pilot burner tip.
5. Keep holding the knob down with one hand. With your other hand, press the push-button sparker firmly once every second. You will hear a sharp mechanical snap with each click.
6. Watch through the small view window near the bottom of the heater. Look for a tiny blue flame to pop to life on the burner bracket.
7. Continue holding the gas control knob down for 30 to 60 seconds after the flame catches. The flame must heat the safety heat sensor rod (thermocouple) so it generates a micro-voltage current that holds the internal magnetic gas valve open.
8. Release the knob slowly. Look through the view window to ensure the flame stays lit, then turn the gas control knob to ON.
9. Turn the temperature dial to your desired setting, ideally around 120 degrees Fahrenheit (marked "HOT"), to balance comfortable water with scald prevention. The main burner will fire up with a gentle whoosh.

How do you light an older Rheem water heater?

Older Rheem units and atmospheric models do not have a sealed glass window or a built-in push-button sparker. Instead, they have a removable metal cover that exposes the burner area. Lighting these units requires an external flame source and steady hands.

If your water heater is installed inside a manufactured housing utility closet, drafts and restricted air vents can complicate ignition; you can read more about heating these enclosed spaces in our guide on the best heater for mobile home setups.

Follow these steps to safely light an open-panel Rheem water heater:

1. Turn the temperature dial to "VACATION" or "LOW", then switch the gas control knob to OFF. Wait a full 10 minutes for any gas fumes to clear from the combustion chamber.
2. Lift off the outer metal access door, then slide or unclip the inner metal heat shield to expose the burner assembly.
3. Use an extended butane barbecue lighter or a long fireplace match. Never use a standard pocket lighter or matchbook, which forces your fingers too close to the burner opening.
4. Turn the gas control knob to PILOT.
5. Press and hold down the PILOT knob completely to start the gas flow.
6. Bring the flame of your lighter directly to the pilot burner tip next to the safety heat sensor rod until the gas catches with a soft hiss.
7. Keep holding the control knob down firmly for 60 seconds so the sensor rod heats up fully.
8. Release the knob gently and confirm the flame stays burning. Replace both the inner heat shield and outer metal door securely to block room drafts.
9. Turn the gas control knob to ON, then raise the temperature dial to your desired warmth level.

Why won't your Rheem pilot flame stay lit?

The most common problem homeowners encounter is a pilot flame that burns while holding the knob down, but dies the instant they let go. This almost always points to the safety heat sensor rod (thermocouple or thermopile) failing to detect heat.

Here are the primary causes behind a Rheem pilot flame that refuses to stay lit:

• Carbon soot buildup: Over time, fine soot coats the copper tip of the safety heat sensor rod. Soot acts as an insulator, keeping heat from warming the metal. Without adequate heat, the rod cannot produce the electrical signal that keeps the gas valve open. Wiping the cold rod gently with a fine emery cloth or scouring pad clears this residue.
• Misaligned sensor rod: The tip of the sensor rod must sit directly in the upper third of the pilot flame. If the rod was bumped or bent during cleaning, the flame will miss the sensor, causing the safety valve to shut off fuel as soon as you let go of the knob.
• Worn-out thermocouple: Constant exposure to high heat eventually breaks down the internal wiring of the sensor rod. Once degraded, it stops generating voltage no matter how hot the flame gets. Replacing a faulty thermocouple is an inexpensive, routine repair.
• Air trapped in the gas line: If the gas supply was recently shut off, air fills the supply pipe. You may need to hold the pilot knob down for two or three consecutive cycles to bleed the air out before pure gas arrives.
• A clogged air intake screen: Modern Rheem units feature a flame arrestor screen under the burner. In dusty basements or laundry rooms, lint and pet dander can coat this screen, choking off the oxygen needed to support combustion.
• Chilling basement or garage drafts: If your water heater sits in an uninsulated garage where freezing winter drafts chill the pipes and flame assembly, pairing the space with a dedicated unit from our review of the best electric heater for garage with thermostat can help protect your plumbing lines from freezing and reduce draft turbulence around the burner compartment.

When should you stop and call a professional?

Relighting a water heater is straightforward, but certain warning signs indicate mechanical failure or serious safety risks. Gas appliances demand caution, and forcing a faulty unit to run can lead to carbon monoxide poisoning or fire.

Stop your attempts and contact a licensed plumber or gas technician if you notice any of these red flags:

• Persistent gas odors: You smell gas before touching the dials, or the odor grows stronger after waiting through the 10-minute clearing window.
• Soot and scorching: You see black soot marks, blistering paint, or heat discoloration around the outer jacket, draft hood, or burner door. This points to backdrafting, meaning exhaust fumes are spilling into your living space.
• A yellow or fluttering flame: A normal pilot flame is a steady, sharp blue cone. A lazy orange or yellow flame indicates improper combustion and dangerous carbon monoxide production.
• Repeated shutoffs: The pilot flame lights but drops out every time you release the knob, even after cleaning the sensor rod and bleeding air from the line.
• Blinking error codes: Electronic Rheem valves feature an LED diagnostic status light. If this light flashes repeated error patterns, an internal safety switch has tripped or the valve requires service.
• Stuck or damaged controls: The gas control knob will not turn, feels stripped, or shows signs of water leaking from behind the thermostat dial box.

FAQs

How do you know if the pilot flame actually caught?

Look directly through the small view window (sight glass) located at the bottom of the tank. A lit pilot appears as a steady, bright blue flame roughly the size of a thumbnail resting on the burner bracket. On newer Rheem models with an electronic thermostat dial box, the LED status light will also begin pulsing green once the sensor warms up.

How long must you wait between failed lighting attempts?

Wait at least 10 full minutes between lighting attempts with the gas control knob set to OFF. Pushing the pilot knob releases raw gas into the combustion chamber. Waiting allows those unburned fumes to draft harmlessly out through the vent pipe, preventing a sudden flash fire on your next spark attempt.

What does a blinking light on the control box mean?

The blinking LED on an electronic Rheem gas control valve shows the operating condition of your heater. A single green flash every three seconds signals normal operation with a stable flame. Multiple rapid flashes or repeating blink sequences indicate diagnostic error codes, such as a tripped thermal cutoff switch or a weak sensor signal.

Can a draft blow out your pilot light repeatedly?

Strong airflow from drafty crawlspaces, open garage doors, or unsealed basement windows can easily blow out an active pilot flame. In addition, high winter winds can create downdrafts inside the chimney flue that push air down into the burner chamber. If your pilot flame snuffs out whenever it is windy outside, inspect your vent draft hood or call a technician.