Waking up to a cold shower is a jarring way to discover your water heater has a problem. Before you call a plumber, work through these troubleshooting steps — many water heater issues have simple fixes that do not require professional help.

No Hot Water? How to Troubleshoot Your Water Heater

Electric Water Heaters

Check the Breaker

Electric water heaters run on a dedicated 240-volt circuit. Check the electrical panel for a tripped breaker. Reset it by turning it fully off and then back on. If the breaker trips again, there is a short in the heater or wiring — call a licensed electrician.

Check the Reset Button

Electric water heaters have a high-temperature cutoff switch — a red reset button located behind the upper access panel. Open the panel (after turning off the breaker), press the red button firmly, and restore power. If the heater starts working, the cutoff tripped due to overheating. If it trips repeatedly, the thermostat or heating element is likely faulty.

Check the Thermostats

Electric heaters have two thermostats — upper and lower — behind the access panels. With the power off, use a multimeter to test continuity across each thermostat. A thermostat that shows no continuity is failed and needs replacement.

Check the Heating Elements

Electric heaters have two immersion elements. A failed element is the most common cause of no hot water. With the power off, disconnect the element wires and test resistance across the element terminals with a multimeter. A working element shows 10 to 20 ohms of resistance. An open reading (infinite resistance) means the element has burned out.

Replacing a heating element is a DIY-friendly repair. Drain the tank, unscrew the old element with an element wrench, and screw in the new one. Refill the tank completely before restoring power — energizing an element in an empty tank burns it out instantly.

Gas Water Heaters

Check the Pilot Light

If you have a gas water heater with a standing pilot, look through the inspection window at the base. A small flame should be visible. If the pilot is out:

Turn the gas valve to OFF and wait five minutes for any gas to dissipate.
Turn the valve to PILOT.
Press and hold the pilot button while using a long lighter or the built-in igniter to light the pilot.
Hold the pilot button for 30 to 60 seconds after the flame appears, then release.
Turn the valve to ON.

If the pilot will not stay lit, the thermocouple is likely failed. The thermocouple is a safety device that senses the pilot flame and keeps the gas valve open. A new thermocouple costs $10 to $20 and is a simple replacement.

If you smell gas at any point, leave the area immediately and call your gas utility’s emergency line. Do not flip any switches or use any ignition sources. Always hire a licensed professional for gas line repairs.

Check the Gas Supply

Verify the gas shutoff valve on the supply line to the heater is fully open. Check other gas appliances in the house — if they are also not working, the problem may be with the gas supply, not the heater.

Check the Thermostat

Gas water heaters have a single thermostat on the gas valve. It should be set between 120 and 130 degrees Fahrenheit. If it was accidentally turned down, adjust it and wait an hour for the water to heat.

Both Types: Common Issues

Not Enough Hot Water (Rather Than None)

If you get some hot water but it runs out quickly:

Undersized heater: A 40-gallon tank may not supply enough hot water for a large family, especially during peak usage (morning showers back to back).
Sediment buildup: Minerals settle at the bottom of the tank over time, reducing capacity and insulating the bottom element (electric) or burner surface (gas) from the water. Flush the tank annually to prevent this — see the water heater maintenance guide.
Dip tube failure: The dip tube directs cold water to the bottom of the tank. If it breaks, cold water mixes with hot water at the top, reducing output temperature.
Crossover: A failed mixing valve or single-handle faucet can allow cold water to backflow into the hot water line. Test by turning off the cold water supply to the heater and opening a hot-water faucet. If water flows, there is a crossover somewhere.

Water Too Hot

If the water is scalding hot:

The thermostat is set too high. Turn it down to 120 degrees.
On an electric heater, a thermostat may be stuck in the ON position, keeping the element running. Replace the thermostat.

Leaking Tank

Water pooling around the base of the heater may indicate a corroded tank. Check the drain valve and the temperature and pressure (T&P) relief valve first — these are the most common leak sources and are easily replaced.

If the tank itself is leaking (visible rust holes or weeping along a seam), the tank has corroded through and the heater must be replaced. Tank leaks cannot be patched.

When to Call a Professional

Handle breaker resets, pilot light relighting, element and thermocouple replacements yourself. Call a licensed professional for:

Gas line work or persistent gas smell
A leaking tank (replacement is needed)
Repeated high-temperature cutoff trips (potential wiring issue)
Any repair you are not confident performing safely

A water heater is a workhorse appliance that runs 24/7. Most problems are straightforward to diagnose with basic tools and a multimeter. Work through these steps systematically and you will identify the cause in most cases.