If your gas water heater is not working, the cause is usually one of four things: no gas reaching the unit, a pilot light that has gone out, a dirty or failing thermocouple, or a faulty gas control valve. Most homeowners can safely check the first three themselves. If those checks don’t bring back hot water, call a licensed plumber.

Below is a safety-first troubleshooting sequence, a quick symptom chart, and clear guidance on where DIY ends and professional repair begins.

Before You Start: If You Smell Gas, Stop

If you notice a rotten-egg odor near the water heater, don’t troubleshoot anything. Leave the house right away, don’t flip light switches or use anything that could spark, and call your gas utility or 911 from outside.

Natural gas has an odorant added so leaks are noticeable. A water heater that has quit and a smell of gas together is a safety issue, not a repair project. Only continue with the steps below if there’s no gas odor.

Why Is My Gas Water Heater Not Working? Quick Symptom Chart

Match what you’re seeing to the most likely cause, then jump to the matching step.

Step-by-Step Gas Water Heater Troubleshooting

Work through these in order. Each step rules out a cause before you move to the next one.

Step 1: Confirm Gas Is Reaching the House

Turn on a gas stove burner or another gas appliance. If nothing in the house has gas, the problem is upstream of the water heater. Contact your gas utility rather than working on the tank.

Step 2: Check the Water Heater’s Gas Shut-Off Valve

Find the manual valve on the gas line feeding the water heater. The handle should run parallel to the pipe, which means it’s open. A valve that got bumped partly closed during other work nearby is a more common cause than people expect.

Step 3: Check the Pilot and Relight It If Needed

Look through the small sight window near the bottom of the tank. If you don’t see a small blue flame, the pilot is out. Relight it by following the instructions printed on your tank’s label, since the sequence varies by model. On most standing-pilot units it looks like this:

1. Turn the gas control knob to OFF and wait the time listed on the label so any gas can clear.
2. Turn the knob to PILOT and press it down.
3. While holding it down, press the igniter button until the pilot lights.
4. Keep holding the knob for the time the label specifies so the thermocouple can heat up.
5. Release the knob, confirm the pilot stays lit, then turn the knob to ON.

Some newer gas water heaters use electronic ignition instead of a standing pilot, and some use a power vent fan. Those models need electricity. If yours has a power cord or is hardwired, make sure it’s plugged in and its breaker hasn’t tripped.

Step 4: Look at the Thermocouple

If the pilot lights but goes out the moment you let go of the knob, the thermocouple is the usual suspect. This small copper rod sits in the pilot flame and tells the gas valve it’s safe to keep gas flowing. When it’s coated in soot or has bent out of the flame, the valve shuts off gas as a safety measure.

Check that the tip sits directly in the pilot flame. Some homeowners gently clean a cool thermocouple with fine sandpaper. If cleaning doesn’t help, the part needs replacing. That’s a common, inexpensive repair, but it has to be seated correctly to work, so it’s reasonable to hand it off if you’re not comfortable working near the burner.

Step 5: Check the Thermostat Setting

If the pilot stays lit but the main burner never comes on, look at the temperature dial on the gas control valve. A dial turned to VACATION or its lowest setting won’t call for heat. Turn it up to your normal setting and listen for the burner to ignite.

If the dial is set correctly and the burner still won’t fire, the gas control valve may have failed internally. Don’t take it apart. That part controls gas flow and needs professional testing and replacement.

Step 6: Don’t Keep Forcing a Safety Shutoff

Modern gas water heaters have built-in safety devices, including a high-temperature cutoff and, on many units, a sensor that shuts the burner down if it detects flammable vapors or a combustion problem. A blinking status light often means one of these has tripped. Look up the code in your owner’s manual. If the unit keeps shutting itself off, stop relighting it. The shutdown is telling you something needs a professional look.

What Temperature Should a Gas Water Heater Be Set To?

The U.S. Consumer Product Safety Commission recommends setting residential water heaters to 120°F. That’s hot enough for everyday household use while greatly reducing the risk of tap water scalds, especially for young children and older adults.

Source: U.S. Consumer Product Safety Commission, “Avoiding Tap Water Scalds” (2012)

Dial markings on gas water heaters aren’t precise, so check the actual temperature. The CPSC suggests holding a thermometer under the tap first thing in the morning or at least two hours after anyone has used hot water, then adjusting the dial and rechecking.

Also keep the season in mind. In Northern Virginia winters, the water coming into your home is much colder, so a heater that’s working fine can take longer to recover and may seem weaker than it does in summer.

When Should You Call a Plumber for a Gas Water Heater?

Call a licensed plumber when the basic checks don’t restore hot water or when the problem involves gas, venting, or the tank itself. Specifically:

• The pilot won’t stay lit after the thermocouple is cleaned or replaced. The gas control valve is the likely culprit.
• The burner won’t fire even with the pilot lit and the thermostat turned up. This also points to the gas control valve.
• Water is pooling at the base. A leaking tank can’t be patched and needs replacement. Fittings and relief valve leaks can often be repaired.
• You hear popping or rumbling. Heavy sediment on the tank bottom makes the burner work harder and can shorten the heater’s life.
• The safety shutoff keeps tripping. Repeated shutdowns can signal a venting, combustion, or overheating problem.
• The heater is near the end of its service life. The U.S. Department of Energy notes that storage water heaters typically last 10 to 15 years. An older unit with repeated failures is often a better candidate for replacement than another repair.

Anything involving the gas line, venting, or installing a new tank is work for a licensed professional, both for safety and to meet building code.

Repair or Replace?

A younger heater with a single failed part, such as a thermocouple, igniter, or relief valve, is usually worth repairing. A leaking tank, or an older unit that keeps breaking down, usually isn’t. If replacement makes more sense, you can compare tank water heater installation with a switch to a tankless water heater before you decide.

Frequently Asked Questions

Why does my gas water heater pilot light keep going out?

The most common cause is a dirty, bent, or worn-out thermocouple that can’t sense the pilot flame, so the gas valve shuts off. Drafts near the unit, a clogged pilot opening, or a failing gas control valve can also cause it. If cleaning and repositioning the thermocouple doesn’t fix it, have a plumber test the thermocouple and valve.

Is it safe to relight a water heater pilot light myself?

Yes, as long as you don’t smell gas and you follow the lighting instructions on your tank’s label exactly. Turn the control off and wait before relighting so any gas can clear. If you smell gas at any point, stop, leave the house, and call your gas utility from outside. Never relight a pilot that keeps going out repeatedly.

Why do I get hot water for a moment and then it turns cold?

A broken dip tube is a common cause. The dip tube sends incoming cold water to the bottom of the tank to be heated. When it breaks, cold water enters near the top and mixes with the hot water at the outlet, so the shower turns lukewarm quickly. It’s a manageable repair, but the tank has to be drained to fix it.

Can I still use water if my gas water heater isn’t working?

Yes. Your cold water supply runs separately from the water heater, so sinks, toilets, and cold-water appliances keep working. The exception is a leaking tank. In that case, close the cold water inlet valve above the heater and turn the gas control to OFF to limit water damage until a plumber can look at it.

What are early warning signs that a gas water heater is failing?

Watch for water that doesn’t get as hot as it used to, hot water that runs out faster, rusty or discolored hot water, popping or rumbling sounds, and moisture or drips around the base or fittings. Any visible leak deserves prompt attention, since a small drip can turn into a tank failure.

Get Your Hot Water Back With Kinnett Plumbing

If you’ve worked through these checks and still have no hot water, Kinnett Plumbing can diagnose the problem and handle the repair or replacement. We’re a family-owned Northern Virginia plumber, licensed, bonded, and insured, with a 4.9-star rating across 811 reviews. We give you an honest assessment of whether repair or replacement makes sense, with no upsell pressure, and offer discounts for military members, teachers, police officers, and firefighters.

Call (703) 878-3154, request service online, or learn more about our water heater repair and replacement services. If your heater is leaking or you’re dealing with an urgent problem, see our emergency plumbing service.