No Hot Water in the House? 5 Causes, Easiest First

No hot water at all is rarely a dead water heater. Most often the heater has lost its power, its gas or its flame, or someone changed a setting. Those you can check in a few minutes without opening anything.

Start with one question: is it every hot tap, or only one? One faucet or shower running cold points at that fixture, not the heater. Every tap cold points at the heater. Hot water that turns lukewarm after a few minutes is a third story, and it points at the tank itself.

Start With These 2-Minute Checks

1. 1Open the hot tap at the kitchen sink and at one other fixture for a minute. If only one of them stays cold, skip to cause 5.
2. 2Find out what kind of heater you have. A tank with a gas pipe and a flue pipe on top is gas, a tank with a thick cable and no flue is electric, a box on the wall is tankless.
3. 3Look at the floor around the heater. Water there means a leak, and that comes first: see water heater leaking.
4. 4On a gas heater, check whether the stove or another gas appliance still works. If none does, the gas supply to the house is off, and the gas company is the one to call.

1. Electric Heater: Tripped Breaker or Reset Button

An electric water heater runs on its own 240-volt double breaker. If that breaker trips, the tank goes cold within hours. A second safety switch, the red reset button behind the upper access panel, cuts the power when the water gets too hot.

1. 1At the breaker panel, find the double breaker marked for the water heater. If it sits in the middle or the off position, push it fully off, then back on once. Do not open the panel itself.
2. 2If it trips again right away, leave it off. A breaker that trips twice points to a fault in the heater or its wiring, and an electrician needs to find it.
3. 3If the breaker stays on and the water is still cold a few hours later, the reset button has probably tripped, or a heating element or thermostat has failed.
4. 4Have a plumber or an electrician check the reset button. It sits next to 240-volt terminals, and a button that tripped once usually trips again until the failed thermostat or element is replaced. HomeAdvisor puts a professional element replacement at about $200 to $300.

2. Gas Heater: The Pilot Is Out or the Gas Is Off

A gas tank heater needs a small flame, the pilot or an electronic igniter, to light the burner. If that flame goes out, the burner never lights and the tank cools down overnight.

1. 1Find the gas control on the front of the heater. If the knob is set to Pilot or Vacation, someone turned the heater down. Set it back to its normal mark, then give the tank an hour or two to heat.
2. 2Look through the small window near the bottom of the tank for a flame. Many newer heaters have no window but a status light that blinks a code; the meaning is printed on the label.
3. 3If the pilot is out, the lighting steps are on the label on the heater. Follow them exactly, or have a plumber do it if you have never done it before.
4. 4A pilot that will not stay lit usually means a worn thermocouple or flame sensor, or a dirty pilot. Those parts sit on the gas line, so a plumber replaces them.
5. 5Hot water again after relighting but cold the next morning means the pilot keeps going out. Book the plumber rather than relighting it every day.

3. Tankless Heater: Error Code or Too Little Flow

A tankless heater only fires when enough hot water flows through it. Rinnai lists a minimum activation flow of about 0.4 gallons per minute on many of its models, so a tap opened only a little, or a faucet with a clogged aerator, may never switch it on.

1. 1Read the display or the status light on the heater and look the code up in the manual. Many codes point to gas, venting or flow and tell you who to call.
2. 2Open the hot tap fully at the kitchen faucet. If hot water comes there but not at a low-flow bathroom tap, the flow at that tap is too low to switch the heater on.
3. 3Unscrew the aerator at the faucet that runs cold, rinse out the grit and scale, and screw it back on.
4. 4If every tap is cold and the code points to ignition or flame, check that the gas is on as in cause 2, then call the installer or a plumber.
5. 5In hard water, makers ask for the heat exchanger to be descaled at regular intervals; the manual says how often. A unit that was never descaled can lose heat or show a code.

4. Hot Water Runs Out Fast or Turns Lukewarm

If the water starts hot and turns lukewarm after a few minutes, the heater works but holds less hot water than it should. Sediment on the bottom of the tank, a broken dip tube that lets cold water mix with the hot at the top, or on an electric heater a dead lower element are the usual causes. Popping or rumbling while the tank heats is the sound of sediment, and flushing the tank helps.

1. 1On a gas heater, check the dial on the gas control first. Energy.gov recommends 120°F for most homes; a dial turned to Warm or Vacation feels like a broken heater. On an electric tank the thermostats sit behind the access panels next to 240-volt terminals, so leave them to a plumber or an electrician.
2. 2To flush, turn the heater off before anything else: breaker off for electric, gas control to Pilot for gas. Let it stand a few hours so the water cools, because tank water can scald.
3. 3Close the cold water valve on the pipe above the heater, open a hot tap somewhere in the house, attach a garden hose to the drain valve at the bottom and lead it to a floor drain or outside.
4. 4Open the drain valve and let the tank empty. Sediment comes out as sand or white flakes. Old plastic drain valves can break or leak when opened; if yours looks brittle, leave the flush to a plumber.
5. 5Close the drain valve, open the cold valve and let the tank fill until the hot tap runs steadily with no air in it.
6. 6Only then turn the heater back on. An electric heater switched on with an empty tank can burn out an element almost at once.

5. Only One Faucet or Shower Has No Hot Water

If the kitchen runs hot and only the shower stays cold, the heater is fine. The valve in that fixture is the cause. Under a bathroom sink, first check that the hot shutoff is fully open.

1. 1Turn the water off to that fixture before you take anything apart: at the valve's own stops if it has them, otherwise at the main shutoff, then open the tap to let the pressure out.
2. 2Single-handle shower: the cartridge mixes the hot and the cold, and a worn one can block the hot side. Take the handle off and swap the cartridge for the same brand and model, as in shower leaking.
3. 3Many single-handle showers also have a limit stop under the handle, a plastic ring or tab that sets how far the handle turns toward hot. If it is set too far toward cold, move it one notch, refit the handle and test.
4. 4Bathroom faucet: unscrew the aerator and rinse out the grit.
5. 5A new faucet or cartridge with hot and cold swapped was put in the wrong way round. The maker's instructions show how to turn it.

6. When to Call a Plumber

Some no hot water problems end the DIY part fast.

1. 1Any smell of gas, a pilot that will not stay lit, or a gas control that does not respond: plumber or gas company.
2. 2An electric heater whose breaker trips again, or that stays cold with the breaker on: the reset button, the elements and the thermostats sit next to 240-volt terminals.
3. 3Water around the base of the tank, or rusty hot water: the tank may be failing. HomeAdvisor puts a replacement at about $875 to $1,800 installed.
4. 4A tankless heater that shows the same code after the flow and gas checks.