No Hot Water? What to Check First
Before you assume the water heater is finished, there are a few safe checks that explain a lot of cold showers. Tempe Emergency Plumber runs through them in order, then explains where the homeowner checks stop and a plumber starts.
- 24/7 Emergency Service
- Upfront Quotes
- Same-Day Availability
Is It the Whole House or One Fixture?
Start here, because it saves everyone time. Run the hot tap at two or three different fixtures, including a bathtub, which usually has the simplest valve in the house. If every fixture is cold, the heater or its supply is the problem. If one shower is cold while the kitchen is fine, the heater is probably fine and the fault is in that fixture's mixing valve or cartridge.
A tub or shower valve that has scaled up is very common here. The anti-scald limiter drifts or the cartridge seizes, and the result feels exactly like a water heater problem from inside the shower. That repair is covered under toilet and faucet repair and it is a much smaller job.
Electric Units: Breaker and Reset
If the heater is electric, check the breaker panel. A tripped breaker is worth resetting once. If it trips again straight away, stop and call, because something is drawing current it should not be.
Most electric tanks also have a high-limit reset button behind an access panel. Pressing it once is reasonable if the panel is dry and easy to get to. If it trips again, the thermostat or an element has failed and the unit needs testing rather than another press. Do not remove the access panels or touch anything inside with the power on.
Gas Units: Pilot, Ignition and Gas Supply
On a gas heater, look at the status light or the indicator on the gas control valve; most modern units flash a code that tells a plumber a great deal. Write it down before you call.
If the unit has a standing pilot and the instructions are printed on the tank, relighting it once by the manufacturer's steps is acceptable. If it will not light, or it lights and goes out again, leave it. That usually means a failed thermocouple or a gas control problem, and repeated attempts do not help. If you smell gas at any point, do not touch switches or the control. Leave the building and call the gas utility from outside.
Running Out Early Is a Different Problem
If the water starts hot and turns cold after a few minutes, the heater is working and something is limiting how much hot water it can hold or deliver. In this valley that is usually sediment. Hard water leaves minerals in the bottom of the tank, they take up volume that used to hold hot water, and on a gas unit they insulate the burner from the water above.
The rumbling or popping sound a lot of tanks make while heating is that sediment: pockets of water boiling underneath it. A flush often restores normal output on a unit that is otherwise healthy, and it is a good deal cheaper than a replacement. A broken dip tube and a failed lower element on an electric unit produce similar symptoms and are also repairs.
Tankless Units and Hard Water
A tankless heater that runs hot then cuts to cold, or refuses to fire at high flow, is very often telling you the heat exchanger is scaled. Manufacturers expect these units to be descaled on a schedule in water as hard as ours, and a unit that has never been serviced will eventually protect itself by reducing output or shutting down.
Note the error code on the display before you call. It points straight at the fault, and it is the difference between a diagnostic visit and a plumber arriving with what the repair needs.
Where It Stops Being a Homeowner Job
Testing elements and thermostats, diagnosing a gas control valve, replacing a thermocouple, flushing a scaled tank properly, changing an anode rod or descaling a tankless unit are all plumber work. So is anything involving the gas line, the venting or a relief valve that has been discharging.
If the tank is leaking from its body rather than from a fitting above it, no check will change the answer. A corroded shell cannot be repaired. Our repair or replacement comparison sets out how that decision is made, including the part most people skip: decoding the manufacturing date from the serial number.
Arrange an Inspection
Before you call, have the make, the model, the approximate age and any error code ready, and know whether the unit is electric, gas or tankless. That short list turns a diagnostic visit into a repair visit. Tempe Emergency Plumber covers water heater repair across the area, and homes in Gilbert and the other newer suburbs are reaching the age where these calls cluster. If the unit is leaking onto the floor as well, see leak detection, or request a visit directly.