No Hot Water? What to Check Before You Call

First, figure out how much hot water is missing

Start by checking more than one faucet. If only one fixture runs cold, the problem is probably a mixing valve or cartridge in that fixture, not the water heater. If every faucet in the house is cold, the heater itself is the likely cause. If the water is warm but not hot, or the hot water runs out much faster than it used to, you are usually looking at a heating problem inside the tank or a sediment issue rather than a complete failure.

Also notice whether the problem started suddenly or slowly. A sudden loss of hot water often points to the pilot, igniter, gas supply or a tripped breaker. A slow decline over weeks usually points to sediment buildup, a failing heating element or a thermostat that is wearing out.

Gas water heaters: check the pilot and the gas

On most gas tank heaters you can look through a small window near the bottom of the tank to see whether the pilot flame is lit. If it is out, follow the relighting instructions printed on the label of your heater. Never use an open flame near a heater if you smell gas. If you notice a rotten-egg smell, leave the house and call your gas utility from outside.

If the pilot lights but goes out again, the thermocouple or flame sensor may be failing, the burner may be dirty, or the venting may not be drawing properly. These parts are safety devices, so repeated outages are a sign to have the heater inspected. Also confirm that other gas appliances, like the stove, are working. If none of them are, the problem is the gas supply, not the heater.

Electric water heaters: check power and elements

Electric heaters run on a dedicated 240-volt circuit. Look at your electrical panel for a tripped breaker labeled for the water heater. If it has tripped, you can reset it once. If it trips again, stop, because that usually means a shorted heating element or a wiring problem that needs a professional.

Many electric heaters also have a high-limit reset button behind an access panel. It trips when the water gets too hot. If it keeps tripping, a thermostat may be stuck. Because these panels expose live wiring, we recommend leaving electrical testing to a licensed technician.

Tankless water heaters: read the display

Tankless units usually show an error code on the front display or the remote controller when something goes wrong. Write the code down before you reset anything, because it tells the technician where to start. Common causes include an ignition failure, a gas supply that is too small for the unit, a blocked air intake or vent, or scale buildup from hard water restricting flow.

Also check that the unit has power. Tankless heaters need electricity even when they burn gas. A tripped GFCI outlet or a power outage can shut the unit down. You can find more detail in our guide to tankless error codes.

When to call a professional right away

Some situations should not wait. Call for help immediately if you smell gas, see water pooling around the base of the heater, notice scorching or soot near the burner, hear loud banging, or see the relief valve discharging water. These signs can indicate a safety concern or a tank that is failing.

If your heater is more than about ten years old and has stopped heating completely, it is also worth talking through replacement. Our repair-or-replace guide explains how we help customers make that decision. For costs, call for a free quote, because the right answer depends on your heater, fuel type and installation location.

• Gas smell near the heater
• Water on the floor around the tank
• Soot, scorching or a yellow flame
• Repeated breaker trips or pilot outages
• A tank older than ten to twelve years

How we fix no-hot-water problems

When you call The Water Heater Warehouse, we ask a few questions about your heater, its age and what you have already checked. Our technician then tests the gas or power supply, controls, safety devices and venting to find the real cause. We explain what we found in plain language and give you clear options before any work begins. Many common parts are stocked on our trucks so the repair can often be completed in a single visit.

Related service

Learn about our emergency water heater repair, or see our water heater repair in Fullerton.

Frequently asked questions