No hot water

Start here: three checks that take five minutes

Before calling anyone, look at the heater itself. These checks are safe for any homeowner and often save a service call or at least point the plumber at the right part.

1. Is it getting fuel or power? On a gas tank, look through the small window near the bottom for the pilot flame. On an electric tank, check the breaker panel for a tripped double-pole breaker labeled water heater. On a tankless unit, read the display for an error code.
2. Is the thermostat turned down? Gas heaters have a dial on the control valve. Someone may have bumped it to VACATION or PILOT. Electric thermostats sit behind access panels, so leave those for the plumber unless you are comfortable with the power off and tested.
3. Is it every faucet or just one? If one shower is cold and the kitchen is hot, the problem is the shower's mixing valve, not the heater.

If the pilot is out, relight it using the steps printed on the heater's label. If it lights and stays lit, you may be done. If it lights and goes out within a minute or two once you let go of the button, the thermocouple is the usual culprit. That is covered on our pilot light and gas valve page.

No hot water at all: the likely causes

Electric heaters have a quirk worth knowing: the upper element heats first, then hands off to the lower one. If the upper element dies, the tank produces no hot water at all, even though the lower element is fine. If only the lower element dies, you get a small amount of hot water that runs out fast.

Hot water that runs out too fast

This is the most common complaint after a cold morning shower, and it has four usual causes.

• A failed lower element on an electric heater. The tank is only heating its top third. The fix is one element and usually lands in the $150 to $400 range.
• A broken dip tube. The plastic tube that carries cold water to the bottom of the tank cracks, so cold water mixes straight into the hot outlet. Bits of white plastic in faucet aerators are the giveaway.
• Sediment. In hard-water areas, minerals settle into a crust on the tank floor that takes up room and insulates the water from the burner. A flush helps if it is not too late.
• The tank is simply too small for the household now. A 40-gallon tank that served two people will not keep up with four. That is a sizing problem, not a repair, and the answer is a larger tank or a tankless unit.

Winter makes all of these worse. Incoming water in northern cities can drop into the 40s in January, which means the heater has to raise every gallon much further than it does in August. A tank that was barely keeping up in fall will fall short once the ground gets cold.

Lukewarm water that never gets hot

Lukewarm water is a different problem from water that runs out. If the very first minute is only warm, the heater is not reaching temperature at all. On a gas tank that points to a weak burner flame, a partly blocked flue, or a thermostat dial set too low. On an electric tank it usually means one element is out and the other is carrying the whole load, or a thermostat is reading wrong.

A mixing valve can also cause it. Many newer installs include a thermostatic mixing valve at the heater outlet to keep tap water at a safe temperature. When those fail, they can blend in too much cold. It looks like a heater problem but is a $150 to $300 valve swap.

Set the heater around 120°F for most homes. That is hot enough for showers and dishes and low enough to cut scald risk. Turning it much higher to fix a short supply wastes energy and speeds up sediment buildup.

When no hot water means it is time to replace

Sometimes the repair math does not work. If the heater is past ten years old, the bottom is crusted with rust, and the part needed is the gas control valve, a new heater is usually the better spend. The same goes for any tank that also shows water around the base.

Replacement for a standard tank usually lands between $1,200 and $3,500 installed, depending on fuel, size, code upgrades and access. Our replacement page explains what goes into that range and how long the swap takes.

Why some homes lose hot water more often

Houses on hard water see more element failures and more sediment, because minerals coat electric elements until they overheat and crack. Homes with high street pressure, above about 80 psi, wear out T&P valves and stress the tank every time it heats. Garages in cold climates make pilots harder to keep lit and stretch recovery time in winter.

If your heater keeps losing heat, ask the plumber to check the water pressure with a gauge at a hose bib and to look at the anode rod while they are there. A pressure reducing valve or an expansion tank costs far less than replacing elements twice a year.

What to tell the plumber when you call

A clear description gets you a better price range on the phone and the right part on the truck. Have these ready:

• Gas, electric or tankless, and the gallons printed on the label.
• The brand and the serial number (it tells the age).
• Whether you have no hot water, a short supply, or only lukewarm water.
• Anything that changed recently: a power outage, a tripped breaker, work on the gas line, a new appliance.
• Whether there is any water on the floor, any smell, or any noise.

Ask what the call-out fee is and whether it is credited toward the repair. That is a normal question and any professional shop will answer it straight.

Questions people ask