Busted Water Heater? Common Problems & How to Fix Them
1. Pilot Light Is Out (Gas Water Heaters)
A gas water heater won’t produce hot water if the pilot light has gone out, which is one of the most common and easiest issues to resolve.
- Turn the gas control knob to the “Off” position and wait 5 minutes for any residual gas to clear.
- Turn the knob to “Pilot,” press and hold it down, then use a long lighter or igniter button to light the pilot flame.
- Hold the knob down for 30–60 seconds after the flame ignites, then slowly release it.
- Turn the knob to your desired temperature setting. If the pilot won’t stay lit, the thermocouple is likely faulty (see below).
2. Faulty Thermocouple (Gas Water Heaters)
The thermocouple is a safety sensor that keeps the gas valve open when the pilot is lit — if it’s worn out, the pilot won’t stay lit and your water heater will not heat.
- Turn off the gas supply valve to the water heater.
- Unscrew the thermocouple from the gas valve assembly (usually a hand-tight nut).
- Pull the thermocouple out of the pilot bracket.
- Take the old part to a hardware store for an exact-length match, or order a universal replacement.
- Install the new thermocouple, relight the pilot, and confirm the flame holds.
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3. Tripped High-Limit Reset Button (Electric Water Heaters)
Electric water heaters have a high-limit safety switch that trips and cuts power to the heating elements if the water gets too hot — often caused by a failing thermostat.
- Switch off the water heater’s circuit breaker in your electrical panel.
- Remove the upper access panel on the side of the tank (usually held by two screws).
- Fold back the insulation carefully to expose the thermostat and reset button.
- Press the red reset button firmly until you hear a click.
- Replace the insulation and panel, then restore power at the breaker.
- Wait an hour and test for hot water. If it trips again repeatedly, the upper thermostat needs replacement.
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4. Burned-Out Heating Element (Electric Water Heaters)
If you’re getting lukewarm water or no hot water at all from an electric unit, one or both heating elements may have burned out and need to be replaced.
- Turn off the circuit breaker for the water heater and verify power is off with a non-contact voltage tester.
- Connect a garden hose to the drain valve at the bottom of the tank and drain it completely.
- Remove the access panel and insulation to locate the heating element.
- Disconnect the wires (note or photograph their positions) and unscrew the element with a heating element wrench.
- Check continuity with a multimeter — no continuity confirms the element is faulty.
- Install a new element of the same wattage and voltage, reconnect wires, refill the tank fully before restoring power.
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5. Sediment Buildup in the Tank
Mineral deposits that settle at the bottom of the tank reduce efficiency, cause rumbling noises, and can eventually overheat or corrode the tank lining.
- Turn off the cold water supply and set the water heater to its lowest setting (or off).
- Connect a garden hose to the drain valve and run the other end to a floor drain or outside.
- Open a hot water tap in the house to allow air in, then open the drain valve.
- Once drained, briefly open the cold water supply to flush out remaining sediment — repeat until the water runs clear.
- Close the drain valve, remove the hose, and refill the tank before restoring power or relighting the pilot.
- To prevent recurrence, flush the tank annually. Consider a whole-house water softener if you have very hard water.
6. Leaking Temperature & Pressure Relief (T&P) Valve
A dripping or leaking T&P valve is a serious concern — it may be discharging properly due to excessive pressure, or the valve itself may have failed and needs replacement.
- First, check if your water pressure is above 80 PSI using a pressure gauge on an outdoor hose bib; if so, call a plumber to install a pressure-reducing valve.
- If pressure is normal, turn off power or gas to the water heater and shut off the cold water supply.
- Place a bucket under the discharge pipe and lift the T&P valve’s lever briefly to test it — water should flow, then stop cleanly when released.
- If the valve continues to drip after testing, it needs to be replaced.
- Drain a few gallons from the tank, unscrew the discharge pipe, then unscrew the old valve with a pipe wrench.
- Wrap the new valve threads with thread-seal tape, screw it in, reattach the discharge pipe, and restore water and power.
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For additional guidance on water heater safety standards and maintenance best practices, visit the U.S. Department of Energy Water Heating resource page.
Frequently asked questions
How do I know if my water heater is completely dead and needs replacing?
If your tank is leaking from the bottom (not from fittings), is more than 10–15 years old, shows significant rust inside or out, or has required multiple repairs in a short period, replacement is usually more cost-effective than continued repairs. A local plumber can give you a professional assessment.
How long does it take for a water heater to recover after relighting or resetting?
Most standard tank water heaters take 30–60 minutes to fully reheat after being reset or relit. Larger tanks (50–80 gallons) may take up to 90 minutes. If no hot water arrives after that time, a heating element or thermostat issue is likely.
Is a busted water heater dangerous to leave running?
It depends on the problem. A leaking T&P valve, gas odor, or visible tank corrosion are safety hazards — shut the unit off immediately and call a professional. A burned-out element or pilot outage is inconvenient but not immediately dangerous, though it should still be repaired promptly.
Can I flush sediment out of my water heater myself?
Yes — flushing is a straightforward DIY task that most homeowners can complete in under an hour with a garden hose and a bucket. The full steps are described in Cause #5 above. Annual flushing significantly extends the life of your water heater and keeps it running efficiently.