Why Is My Water Heater Not Making Hot Water?

The first question is whether your water heater burns gas or runs on electricity, because the two fail in completely different ways. A gas heater has a burner under the tank, a flue pipe out the top and a gas control valve on the front. An electric heater has no flue, a heavy cable into a junction box on top, and one or two small access panels on the side covering the heating elements. Once you know which you have, the symptom narrows it further: no hot water at all points upstream to the fuel, power or ignition, while water that is only lukewarm or runs out fast points to something inside the tank. If you get stuck partway, water heater repair covers both types.

Why is a gas water heater not heating?

A gas water heater that makes no hot water most often has a pilot or burner that is not lighting or not staying lit. Look through the sight glass near the bottom of the tank: no flame at all is the starting point for everything else.

• Pilot out or not staying lit. A standing pilot is held on by a thermocouple or thermopile heated by the flame. If the probe is worn or the pilot flame is weak, the gas valve closes and the burner never fires.
• Flame sensing on electronic-ignition models. Newer gas heaters without a standing pilot prove the flame electronically, and a dirty or failed sensor shuts the burner down after it lights.
• The gas control valve. The valve can fail to open the main burner even with a healthy pilot.
• A tripped flammable-vapor sensor. Many sealed-combustion heaters have a sensor or thermal cutoff that shuts the heater down if it detects vapors or overheating in the burner chamber, often after the flame arrestor screen clogs with lint.
• A draft problem. A blocked or backdrafting flue can trip a spill switch and shut the heater off. Heaters left alone on an oversized chimney are especially prone to this, as our guide to the orphaned water heater chimney risk explains.
• No electricity to a power-vent model. A power-vented gas heater needs its fan to run, so a tripped breaker, an unplugged cord or a power outage means no hot water even with plenty of gas.

On propane, check the tank gauge before assuming a parts failure. A low or empty tank starves every appliance in the house, and our post on a propane furnace that ran out of fuel walks through what happens next, including why the system needs to be checked before gas is restored.

Why is an electric water heater not heating?

An electric water heater that makes no hot water at all usually has no power reaching the elements, either from a tripped breaker or a tripped high-limit switch. Most residential electric heaters have two elements, upper and lower, each controlled by its own thermostat, and the upper thermostat carries a red high-limit reset button.

• Tripped breaker. Water heaters are on a dedicated double-pole breaker. If it has tripped, reset it once.
• Tripped high-limit reset. The high limit cuts power if the water gets too hot. It trips because something failed, often a thermostat stuck on or an element shorted to the tank.
• Failed upper element or thermostat. The upper element heats first. If it or its thermostat has failed, the lower element never gets its turn and the tank stays cold.
• Failed lower element or thermostat. This one gives lukewarm water rather than none, because the upper element still heats the top of the tank.

Why is the water only lukewarm or running out fast?

Lukewarm water or hot water that runs out fast usually means part of the tank is not being heated or part of it is full of something other than water. On an electric heater the lower element is the most common cause: the upper element keeps a small amount of hot water at the top, and it is gone in the first few minutes of a shower.

Sediment is the second cause and applies to both types. Minerals settle at the bottom of the tank, bury the lower element on an electric heater and insulate the tank bottom from the burner on a gas heater, so the heater works harder for less. A gas heater that rumbles or pops while heating is usually telling you about sediment.

Problems that affect gas and electric water heaters alike

Some causes of weak hot water have nothing to do with gas or electricity. The dip tube, a plastic pipe that carries incoming cold water to the bottom of the tank, can crack or break off, so cold water enters at the top and mixes straight into the outlet. A thermostatic mixing valve at the heater, or an anti-scald setting on a shower valve, can be set so far toward cold that the heater looks weak when it is fine. And sometimes demand has simply outgrown the tank: a larger family, a bigger tub or a new body-spray shower can empty a tank that was once plenty.

No hot water symptoms and what they usually point to

What you notice	Gas heater, likely cause	Electric heater, likely cause
No hot water at all	Pilot out, ignition fault, tripped sensor, no gas	Tripped breaker, tripped high limit, upper element
Lukewarm water	Sediment, gas valve, mixing valve setting	Lower element or thermostat, sediment
Runs out much faster than it used to	Sediment or broken dip tube	Lower element, sediment or broken dip tube
Hot at first, then cold for a long time	Demand has outgrown the tank	Demand has outgrown the tank
Stops after the power went out	Power-vent fan has no electricity	Breaker or high limit tripped

Why does a water heater seem weaker in a Twin Ports winter?

A water heater delivers less hot water in a Twin Ports winter because the water coming in from the main or the well is far colder than in summer. The heater has to lift that icy water further to reach the same setting, so the same tank covers fewer minutes of showering and recovers more slowly. That is physics, not a failing heater. Households in South Range, Canosia and Pike Lake on private wells often notice it first. If winter hot water has become a real constraint, the fix is sizing, and our look at tankless water heaters in a cold climate covers how cold incoming water affects that option too.

What can you safely check yourself?

The safe homeowner checks on a water heater are short, and they stop at the first sign of a real fault.

1. On electric, check the breaker and reset it once. If it trips again, leave it off.
2. On electric, with the breaker off, press the high-limit reset once. If hot water returns and then fails again, call.
3. On gas, look for a flame through the sight glass and relight the pilot only by following the label on the tank, once.
4. On propane, check the tank gauge. On a power-vent model, check that the unit has electricity.
5. Check any mixing valve at the heater and the setting on the shower valve before assuming the heater is weak.
6. If the heater is also dripping or puddling, read why a water heater leaks before doing anything else.

When to call about a water heater with no hot water

Call when a reset trips a second time, when the pilot will not stay lit after one proper attempt, when a vapor sensor has shut the heater down, or when the problem is lukewarm water that points to an element, thermostat or dip tube. Testing elements means working on live electrical parts, and gas valves, sensors and venting are technician work. Our diagnostic is $89 and is credited toward the repair when you approve it, and water heater service and replacement explains when a repair makes sense and when an aging tank is better replaced.