Water heater repair

What the symptom usually means

No hot water at all. On gas, the pilot or igniter has failed, the thermocouple has gone, or the gas control valve has died. On electric, it is almost always the upper element or the upper thermostat, or a tripped high-limit switch with a red reset button behind the access panel. A reset that holds is a repair; a reset that trips again within a day is a fault you have not found yet.

Hot water that runs out too fast. Usually the lower element on an electric unit, so the bottom two-thirds of the tank never heats. Also caused by a dip tube that has broken off, letting cold water enter at the top and mix straight into the outlet, and by sediment occupying the bottom of the tank where the water should be.

Lukewarm and never hot. A thermostat out of calibration, a crossed connection somewhere in the house letting cold water into the hot side, often a failed mixing valve or a single-handle fixture cartridge, or a gas burner running dirty.

Rumbling, popping or kettling. Sediment on the tank floor with water boiling underneath it. Noisy rather than dangerous, but it is a marker of how much scale the tank is carrying and how hard the burner is working through it.

Rusty or metallic hot water. If it appears only on the hot side, the tank lining has failed or the anode rod is long gone. On an older unit this is usually the beginning of the end rather than a repair.

Water on the floor. The important distinction is where it is coming from, and it is worth two minutes with a torch before calling anyone. A drip from a fitting at the top, from the T&P discharge pipe, or from the drain valve is a repair. Water appearing from beneath the jacket is the tank itself, and no repair exists for that.

Gas and electric fail differently

Gas units fail at the combustion end. Thermocouples and flame sensors wear out, pilot assemblies clog with dust and lint, gas control valves stick or lose their internal thermostat, and burners collect enough debris to run yellow and sooty. Most of these are parts a plumber carries or can obtain the same day, and a gas heater with a healthy tank often earns two or three combustion repairs across its life.

Venting matters more on gas than anything else on the list. A draft hood that is not drawing, a disconnected or corroded flue, or a rusty pattern above the hood means combustion gases are entering the house. That is not a comfort problem; it is the fault that gets a heater shut off rather than repaired until the venting is corrected.

Electric units fail at the elements and thermostats, and both are inexpensive. An element burns out, scales over, or shorts to the tank; a thermostat sticks or drifts. Diagnosis is straightforward with a meter and the two access panels, and the parts are stocked everywhere. The awkward part is that a scaled element sometimes cannot be withdrawn without fighting hardened deposits inside the tank, and that occasionally turns a cheap repair into a longer visit.

Both share the plumbing-side failures: nipples corroding at the top connections, a leaking drain valve, a failed T&P valve, an expansion tank that has lost its charge, and sediment. Those are the same job on either fuel.

Repair or replace: the honest version

The decision is mostly about the tank, because everything else is a part. A steel tank with a glass lining and a sacrificial anode has a working life, and once that life is over no amount of good components changes the outcome.

Age. Six years or under, repair almost anything. Seven to ten, repair cheap faults and think hard about expensive ones. Over twelve, a failed gas valve or a scaled-in element is money spent on a tank that owes you nothing.

Where the leak is. A fitting, a valve or the T&P is a repair at any age. The tank itself is never a repair, whatever anyone offers to weld or seal.

Cost against replacement. The rough rule is half. A repair approaching half the cost of a new installed unit on a heater past two-thirds of its expected life is a bad trade, and honest advice says so.

What the install will cost separately. This is the part people miss. If the heater is in an attic with no pan and no drain, or if the current install is not to code, replacement carries corrective work with it. That can make a mid-life repair the better decision even when the maths looks marginal.

What actually extends the life of a tank

The anode rod. A magnesium or aluminium rod that corrodes so the tank does not. It is consumable, it is inspectable, and replacing it at five or six years is the single cheapest thing anyone can do to a water heater. Almost nobody does it, which is why so many tanks fail at nine years instead of fifteen.

Draining sediment. Texas water is hard nearly everywhere, and hardness precipitates onto the bottom of a hot tank. On gas, that layer insulates the water from the burner and pushes tank-floor temperatures up. An annual partial drain from the bottom valve helps; a heater that has never been drained in eight years may not drain at all once you try, and forcing it can leave you with a valve that will not reseat.

The T&P valve. The temperature and pressure relief valve is the safety device that stops a water heater becoming something dangerous. It should be tested periodically and it should discharge through a proper pipe terminating where a discharge would be noticed. A T&P weeping regularly is telling you about pressure in the system, not about itself.

Thermal expansion. Where the house has a pressure regulator or a check valve at the meter, the plumbing is a closed system and heated water has nowhere to expand. Without a working expansion tank the pressure spikes every heating cycle, which shortens the life of the tank, the T&P and every fixture in the house. An expansion tank that has lost its air charge is doing nothing, and testing it takes seconds.

Temperature setting. 120 °F is the usual recommendation and the setting most tanks leave the factory on. Higher gives more usable hot water from the same tank and accelerates both scaling and scald risk.

When it is worth calling immediately

Water is running, not dripping. Close the cold inlet valve at the top of the heater. If the heater is gas, turn the control to off or pilot; if electric, switch off the breaker. Then call. A heater running to the floor in an attic or an interior closet does more damage per hour than almost any other plumbing failure in the house.

You can smell gas. Leave, then call the gas utility from outside. Nothing about a water heater is worth investigating with a suspected gas leak in the room.

The T&P is discharging steadily. Either the thermostat has failed and the tank is overheating, or system pressure is too high. Both need attention now rather than at the weekend, and neither is fixed by capping the discharge pipe, which is dangerous and, in every jurisdiction, not permitted.

Soot, scorching or a yellow flame on a gas unit. Combustion faults belong in the same category as gas smells. Shut the heater down and get it looked at.

Everything else, no hot water on an electric unit, a heater running out too soon, a noisy tank, a weeping drain valve, is a normal service call that can wait for a scheduled visit.