No hot water in the house: causes and what to check first

First: is it the whole house or one tap?

Run hot water at a kitchen sink, a bathroom sink and a tub. If one fixture is cold but the others are hot, the water heater is doing its job and the problem is at that fixture, often the shower valve (see hot water in the sink but not the shower). If every tap is cold, or barely warm, the heater itself is the place to look. And if the water is warm but not hot, start with water heater not hot enough instead.

Safety before you touch the heater

A. O. Smith's troubleshooting guide sets these rules before any checks:

• Electric heaters: turn the power off at the circuit breaker before touching anything. Parts stay live even when the heater isn't heating.
• Gas heaters: if you smell rotten eggs or suspect a gas leak, turn off the gas supply valve and call a professional. Don't keep troubleshooting (see water heater smells like gas).
• Hot surfaces: let the heater cool before removing panels. Touching the relief valve while the heater runs can release scalding water.

Quick diagnosis table

Sources: Lennox and A. O. Smith troubleshooting guides.

Electric water heater: breaker, reset button, elements

1. The breaker. A. O. Smith calls a tripped breaker a very common reason an electric water heater stops working. Lennox says a tripped breaker sits in the middle position: switch it fully off, then back on. If it trips again right away, don't keep resetting it; something in the heater is shorting (see water heater keeps tripping the breaker).

2. The red reset button. Electric tanks have a high-limit switch, usually a red button on the upper thermostat behind the access panel, that cuts power if the water gets too hot. Lennox says to turn the power off at the breaker, remove the panel and press the button. A. O. Smith notes the switch often trips because of a grounded heating element or a faulty lower thermostat, so a reset that keeps tripping is a sign of a failed part, not bad luck. Step-by-step help is in how to reset a water heater.

3. The elements. A standard electric tank has an upper and a lower element. A. O. Smith lists faulty elements as a top cause of no hot water, and its guides point to the upper element (then the upper thermostat) when there's no hot water at all, and to the lower element when a little hot water runs out fast. Our guide to testing a bad electric water heater element shows how with a multimeter.

Gas water heater: pilot, gas supply, air screen

1. The pilot. Look through the small window near the bottom of the tank. Lennox says pilots go out from drafts or an interruption in the gas supply, and to relight following the instructions on the heater's label (walkthrough: how to light a water heater pilot light). If it won't stay lit after two or three tries, Lennox says the thermocouple likely needs a technician (see pilot light keeps going out and water heater thermocouple).

2. The gas supply. A. O. Smith says gas supply problems stop the burner from lighting and can put the pilot out. Make sure the gas valve on the line to the heater is open. If your stove or furnace is also out, the problem is upstream of the heater and your gas utility is the call.

3. The air screen. Many newer gas tanks draw combustion air through a screen or filter near the base. A. O. Smith says a blocked screen restricts combustion air and affects the burner, so clear lint and dust and keep the area around the heater open.

Newer gas heaters with an electronic control may also show a status light that blinks a code; the code chart is usually on the heater's label or in the manual (see water heater gas valve).

Tankless water heater: no hot water

A. O. Smith lists four common reasons a tankless unit stops delivering hot water:

• Mineral buildup on the heat exchanger. It recommends descaling every year, more often with hard water (see how to flush a tankless water heater).
• Undersizing. The unit can't keep up when several fixtures run at once.
• Ignition failure from gas supply, venting or the ignition pack.
• Cold water sandwich, a short burst of cold between uses.

More on each in tankless water heater not heating.

After a power outage or a cold snap

If the hot water stopped after the power went out, the heater may need a reset or a pilot relight once power is back. Our guide to a water heater not working after a power outage covers gas and electric models. Which checks apply depends on what your heater runs on. In Harrison, Ohio, census estimates on our town page show 65% of homes heat with electricity; in Powell, Ohio, 80% heat with gas. If you're not sure which you have, a gas heater has a flue pipe on top and a gas line to a control valve near the bottom; an electric one has a cable running into a box on top.

How long until the hot water comes back

Once the breaker, reset or pilot is sorted, the tank has to heat a full load of cold water. A. O. Smith says a gas tank needs about 30 to 40 minutes and an electric tank about 60 to 90 minutes. If nothing changes after that, the fix didn't take (details in how long a water heater takes to heat up).

When to stop and call a technician

Lennox says to call a professional when:

• you smell gas;
• water is pooling around the base of the tank (see water heater leaking from the bottom);
• you still have no hot water after the basic checks;
• the reset button or breaker keeps tripping;
• the relief valve is dripping or hissing (never cap or plug it);
• the heater is 8 to 12 years old or more, the lifespan Lennox gives for tank heaters (see how old is my water heater).

Local pages mentioned

• Powell, OH
• Harrison, OH