Yes, you can light a hot water heater by following the model’s safety label and these steps, with gas shutoff and leak checks first.
Gas models use either a standing pilot or spark ignition. The right method lives on the lighting label near the burner door. This guide gives you clear, step-by-step directions, safe checks, and quick fixes. You’ll see where people get stuck, what each control does, and when to stop and call a pro.
Safety First Before Any Flame
Work in good light and keep kids and pets away. If you smell rotten-egg odor, hear hissing, or feel dizzy, leave the area and call your gas utility or 911 from outside. Don’t flip switches or use phones in the room. Once the space is cleared, only return when the utility or fire crew says it’s safe. State guidance pages such as what to do if you smell gas spell out the same steps.
Heater Types And Controls At A Glance
Different gas heaters use different controls. Match yours by the knob and sight glass on the front, and by the color and wording on the lighting label. The table below helps you identify the setup before you start.
| Heater Type | How It Lights | Where To Look |
|---|---|---|
| Standing Pilot (older) | Manual flame with a match/lighter | Removable access door; small pilot tube at burner |
| Piezo/Ignitor Button | Built-in spark when you press the button | Square or round ignitor button beside gas knob |
| Electronic Control | Integrated spark; status light on control | LED status light and code chart on label |
| Ultra Low NOx | Sealed burner; long reset/ignition sequence | Window with angled view; follow label closely |
| Power Vent | Fan proves draft; then ignition | Fan on top; pressure switch tubing |
| Condensing | Electronic ignition with condensate drain | Plastic drain line; larger control module |
| Mobile Home Rated | Similar to standard with tighter vent rules | Rating plate says “Mobile Home” |
| LP/Propane Units | Same steps with propane supply | Rating plate shows “LP” fuel |
How To Light A Hot Water Heater Safely (Quick Start)
Here’s the safe sequence used across brands. Read your label end-to-end first. If anything conflicts, your label wins. If the smell of gas returns at any point, stop and leave.
1) Set Up The Area
- Vent the room by cracking a door.
- Gather a flashlight and a long grill lighter only if your label calls for a match.
- Turn the gas valve on the supply pipe so the handle lines up with the pipe.
2) Locate The Controls
Find the gas control knob (OFF–PILOT–ON), the ignitor button (if present), and the sight glass. Some units need you to remove a small panel to see the flame.
3) Turn Gas Control To OFF
Wait five full minutes to clear any unburned gas. This wait is not optional.
4) Move Knob To PILOT And Hold It Down
Press and hold the knob to send gas to the pilot. Keep holding while you light.
5) Light The Pilot
- With Ignitor: Click once per second up to 90 seconds. Watch for a steady blue flame. Many models show success with a slow, steady status light.
- With Match: Insert the lighter to the tip of the pilot tube and spark it while holding the knob.
6) Keep Holding For 30–60 Seconds
This heats the sensor. If the flame looks weak or yellow, release and repeat after another five-minute wait.
7) Turn Knob To ON
Set the temperature to “HOT” or about 120°F. The main burner should start within a minute.
Lighting A Hot Water Heater Pilot — Brand-Specific Notes
Many AO Smith and Rheem models use an ignitor you click repeatedly while holding the knob. Units with a status light need a slow, steady flash to show success. If the light never flashes, relight again after the five-minute wait. New installs can take a few tries while air purges from the line. For button timing and status codes, see the maker’s guide such as AO Smith pilot relight.
What The Flame Should Look Like
A healthy pilot is small, steady, and blue, touching the sensor tip. The main burner is blue with short orange tips only at start-up. Soot, lifting flames, or a roar point to a draft or air problem. Shut it down and call a pro if flames leave the burner area.
Common Mistakes That Stop A Relight
- Skipping the five-minute wait after turning to OFF.
- Letting go of the knob too soon, so the sensor never heats.
- Clicking the ignitor too fast; one press per second works best.
- Trying to light with the gas supply valve closed.
- Missing the pilot orifice with the lighter and only heating the air.
Quick Checks If The Pilot Won’t Stay Lit
Work through the fast list below. Stop and call a licensed tech if you see scorch marks, melted wire covers, loose venting, or water in the burner tray.
| Symptom | Likely Cause | What To Try |
|---|---|---|
| Pilot lights then quits | Weak thermocouple or dirty tip | Brush the tip; if no change, have the part replaced |
| No spark at all | Ignitor not grounded or worn | Check wire seated; many need part replacement |
| Spark but no flame | Air in line or clogged orifice | Repeat after five minutes; pro can clean orifice |
| Flame yellow or lazy | Lack of combustion air | Open a door; clear dust; check vent fan on power-vent |
| Burner booms on start | Delayed ignition | Shut down; call a pro for cleaning and checks |
| Status light never flashes | Failed sensor/control | Power cycle per label; service if still no flash |
| Water smells like sulfur | Tank bacteria/anode reaction | Pro flush and anode options |
Where The Exact Steps Live On Your Heater
The fastest way to match steps is to read the lighting instruction label glued to the jacket. The label uses your control’s icons and tells you the right hold times and status light patterns. If the label is torn or stained, scan the model number on the rating plate and pull the PDF from the maker.
Tool Prep And Small Parts
You usually need only a flashlight and a long grill lighter for old standing-pilot units. A soft brush helps clean a dusty thermocouple tip. Keep a new AA or D cell if your power-vent or controller runs on batteries. If your ignitor is cracked or the wire is loose at the module, a new part fixes many no-spark complaints.
When You Shouldn’t Relight Today
Skip a relight if the vent cap is gone, the vent is crushed, or rainwater dripped into the burner area. Skip it if you see scorch marks, melted paint, or a warped burner door. Skip it if floodwater ever reached the base. Call a licensed tech or your gas utility for inspection before trying again.
Small Differences By Fuel And Draft
Natural Gas Vs. Propane
Propane models use the same motions but the jets are sized for LP. Don’t swap parts between fuels. The rating plate lists the fuel type.
Atmospheric Vs. Power Vent
Power-vent heaters run a fan before lighting. If the fan doesn’t start, the safety switch won’t let the spark fire. Fix the fan issue first.
Temperature And Scald Safety
Set 120°F on the dial unless your maker calls for a different mark. This setting trims burn risk while keeping showers steady. Families with young kids or elder members should test with a kitchen thermometer at a sink and nudge the dial if needed.
Short Glossary Of Controls
- Gas Control Valve: The box with the knob and sometimes a status light.
- Thermocouple/Flame Sensor: The tip the pilot heats so gas keeps flowing.
- Ignitor: The button that clicks to make a spark.
- Draft Hood: The bell at the top that feeds exhaust to the vent.
- Sight Glass: The small window where you watch the flame.
Tankless Note So You Don’t Waste Time
Tankless units don’t have a standing pilot. They spark on demand when water flows. If a tankless won’t fire, check the gas shutoff and the vent intake, clean the cold-water inlet screen, and review the fault code on the display. Your manual lists the exact reset steps. Lighting a pilot isn’t part of tankless care.
Time, Cost, And When A Pro Pays Off
A careful relight usually takes ten to twenty minutes. If parts are worn, a thermocouple or ignitor kit is a modest parts cost, while a control valve or power-vent motor costs more. A pro visit buys testing for leaks, draft, and combustion. That call is smart if the heater is old, was flooded, or sits in a tight closet.
How This Guide Was Built
Steps here align with major maker instructions and public safety guidance. For status light patterns and button timing, see AO Smith pilot relight. For gas odor safety, see state pages such as what to do if you smell gas. Those resources back the sequences in this guide and match what you’ll read on the sticker fixed to your tank.
Recap: How To Light A Hot Water Heater Without Headaches
Read the label, clear the room, set the knob to OFF and wait five minutes, hold at PILOT, spark once per second, keep holding for up to a minute, then turn to ON and set 120°F. If the pilot drops out or the status light won’t flash, move to the checks above or call a licensed tech. If you came searching for how to light a hot water heater after a storm or remodel, give the vent and gas shutoff a close look first. If your partner asked you how to light a hot water heater because showers went cold, the same steps will get you hot water again without guesswork.