No hot water? What to check first — and what's pro-only

The shower runs cold and nothing has changed that you can think of. No hot water is one of the more disruptive things a house can throw at you, and the cause ranges from a five-minute reset to a tank that has reached the end of its life. A few of the checks are safe to do yourself, so it is worth ruling those out before you book anyone.

One thing before any troubleshooting, and it only applies to a gas heater. If you smell gas — a rotten-egg or sulfur smell near the unit or anywhere in the house — stop. Do not touch light switches or anything electrical, do not try to relight the pilot, leave the building, and call your gas utility's emergency line or 911 from outside. That is an emergency, not a repair booking. Come back to the checks below only after the gas company has made the property safe.

First, know which kind you have

The first checks depend on whether your heater runs on gas or electricity, and it is easy to tell. A gas unit has a burner and a flame, a flue or vent pipe out the top, and usually a dial or control box low on the front. An electric unit has a thick power cable running to it and no flue, and it is fed by its own breaker in the panel. A tankless unit — gas or electric — hangs on the wall instead of sitting on the floor and heats on demand.

What's safe to check yourself

• The breaker — for an electric heater, find its breaker in the panel and see whether it has tripped. Reset it once, fully off and then on. If it trips again right away, stop and call a pro. A breaker that keeps tripping is doing its job and pointing at a fault.
• A high-temperature cutoff — many electric heaters have a small red reset button on the panel behind an access cover on the front of the tank. If it has popped, pressing it back in can restore heat. If it trips again, leave it for a pro rather than resetting it over and over.
• The thermostat setting — a dial that has drifted or been turned down, or someone setting a vacation mode, can leave you with lukewarm or no hot water. Nudge it back to a normal setting and give the tank time to recover.
• Recent heavy use — if several showers, a bath, and the laundry all ran back to back, you may simply have drained the tank and it needs an hour or two to catch up. That is normal, not a fault.
• The pilot on an older gas unit — some older gas heaters have a standing pilot with clear lit instructions printed on the unit. If yours does and the pilot is out, you can follow those instructions to relight it. If it will not stay lit, or the unit uses electronic ignition rather than a standing pilot, stop and book a pro — do not keep trying.

What the signs are telling you

• Lukewarm water everywhere, never truly hot — on an electric heater this often means one of the two heating elements has failed, so the tank only half-heats. That is a pro repair inside the tank's wiring.
• Hot water that runs out much faster than it used to — sediment building up in the bottom of the tank steals capacity, and a failing lower element or dip tube can do the same. Worth having looked at rather than lived with.
• A pilot or gas burner that won't stay lit — often a thermocouple or flame sensor that can no longer confirm the flame, or a dirty pilot assembly. Those sit at the gas valve and are a pro's job.
• Rumbling, popping, or banging from the tank — usually sediment boiling under a layer of scale. It is more an efficiency and lifespan problem than an immediate danger, but it is a sign the tank is aging.
• Water pooling under the tank — see the next section. A tank leaking from its body does not get repaired, and it will not get better while you wait.
• Rusty or discolored hot water, or a rotten-egg smell in the water itself — points at corrosion inside the tank or a spent anode rod, and needs a pro to judge whether the tank is still sound.

Water under the tank — what to do now

If there is water pooling under or around the heater, shut off the cold water supply at the valve on top of the unit, and cut its power — the breaker for an electric heater, or the gas control valve for a gas one. Then look at where the water is coming from. A drip at a fitting or a supply connection is often a repair. Water seeping from the body of the tank itself is not — a tank that has rusted through gets replaced, not patched.

One line that is not optional. The temperature and pressure relief valve — the T&P valve, usually on the side or top with a pipe running down toward the floor — is the tank's core safety device. It is designed to release if pressure or temperature climbs too high. If it is dripping, that can mean it is doing its job or that it needs replacing, and that is a pro's call. Never cap, plug, or block that valve or its discharge pipe to stop a drip. Sealing it turns a working tank into a pressure hazard.

What's pro-only, every time

Gas lines, the gas control valve, and the burner assembly on a gas heater are licensed-pro work — not something to test, adjust, or take apart yourself. On an electric unit, the heating elements, the thermostats, and the wiring all sit behind an access cover on a live circuit, and are a pro repair. Replacing the T&P valve, the anode rod, or the tank itself is pro work as well. And never defeat a safety device to force hot water — do not cap the T&P valve, and do not keep resetting a breaker or a high-limit cutoff that keeps tripping. A heater that shuts itself down is usually protecting you, not malfunctioning.

Repair or replace

Whether to repair or replace usually comes down to age and where the failure is. Heating elements, thermostats, thermocouples, gas valves, and anode rods are wear parts and normal repairs. A tank that has rusted through and is leaking from the body is not repairable — that is a replacement, whatever its age. A tank near the end of its expected life that needs a major part is often a closer call, and a pro should show you the condition of the unit and walk you through both options before quoting a new one, rather than quoting a replacement sight unseen.

Describe what your heater is doing — no hot water, water that runs cold fast, a pilot that won't stay lit, a puddle underneath — and Roger books one vetted, licensed local pro and confirms the appointment time with you. You see a price range up front, and the pro confirms the price in person after seeing the unit. Homeowners pay Roger nothing, and Roger does not add a markup on the pro's price.