Hot Water Runs Out Fast? Causes and Fixes

Hot water usually runs out fast because the heater is not heating all the water in the tank. On an electric heater, a failed lower heating element is the most common cause. Other causes are sediment, a broken dip tube, a low thermostat setting, or a tank that is too small. Check when it started and whether it affects every tap.

When the shower goes cold after a few minutes, it feels like the heater is failing. Sometimes it is. Sometimes the tank is simply too small, or winter has made the incoming water colder. This guide helps you work out which.

Why does my hot water run out so fast?

• A failed lower heating element (electric heaters). Most tanks have two elements. The lower one does most of the heating. If it fails, you only get the small amount the upper element warms.
• Sediment in the tank. Minerals settle at the bottom and take up room. They can also insulate the water from the heat, so the heater works harder for less hot water.
• A broken dip tube. The dip tube sends cold water to the bottom of the tank. If it cracks, cold water mixes with hot at the top, and your water cools quickly. Bits of plastic in aerators and showerheads are a clue.
• The thermostat is set too low or faulty. A low setting gives you less hot water before it is mixed down.
• A tank that is too small. More people, more showers and more appliances use up the tank sooner.
• Colder incoming water in winter. Ground water can be much colder in winter, so the heater needs longer to catch up.
• High-flow showerheads or fixtures. A large flow drains the tank faster.
• An aging heater. Old tanks with scale and weak parts struggle.
• Gas heater problems. A dirty burner or a weak flame heats slowly.

What the pattern tells you

How to fix it

1. Check for a breaker or a pilot problem. An electric heater with a tripped breaker will go cold. If the breaker trips again, see a water heater that keeps tripping the breaker.
2. Check the temperature setting. Many manufacturers set heaters to 120°F, which is also a common safety recommendation. Going higher raises scald risk, especially for children and older adults. If you adjust it, do it carefully, and mix at the tap.
3. Think about demand. Count how many showers, loads and dishwashers run back to back. If everyone showers in a row, the tank may be too small.
4. Check the showerheads. A very high flow rate can empty the tank quickly. A lower-flow head may stretch your supply.
5. Flush the tank. Draining a few gallons from the bottom can clear sediment, and many manufacturers recommend doing it yearly. See the steps below.
6. Look at the elements and thermostats (electric). With power off at the breaker, a technician or confident DIYer tests the elements with a meter. Replacing a failed lower element is a common, modest repair.
7. Inspect for a broken dip tube. If plastic bits are clogging faucets, the dip tube may need to be replaced. This is a plumber's job on most tanks.
8. Check the age. Find the date on the label. A tank around 10 to 12 years old and failing is often a candidate for replacement.

How to flush a water heater

Flushing is routine maintenance and often helps with sediment. The steps differ by model, so follow the manual.

1. Turn off the electricity at the breaker, or set a gas heater to Pilot or Off.
2. Turn off the cold water supply to the heater.
3. Open a hot tap in the house to let air in.
4. Attach a garden hose to the drain valve at the bottom and run it to a drain or outdoors.
5. Open the drain valve and let the water flow. It may be cloudy or gritty at first.
6. When it runs clear, close the valve and remove the hose.
7. Open the cold supply, and let the tank fill. Keep the hot tap open until water runs steady, then close it.
8. Restore power or gas.

If the drain valve is clogged or leaks, or if the tank is very old, call a plumber. An old valve can break when you open it.

Is your tank big enough?

Look for the yellow EnergyGuide label on the heater, which lists its first-hour rating, the amount of hot water it can deliver in the first hour. Compare it with how much hot water your household uses at the busiest time. A bigger tank, or a heater with a higher first-hour rating, gives more reserve. A tankless heater gives hot water on demand, but it has its own limits, such as a minimum flow rate and a maximum temperature rise in cold winters.

Is it worth repairing or replacing?

A thermostat, a heating element or a flush cost little compared with a new heater. A failed dip tube is a moderate repair. If the tank is leaking, rusted or more than about 10 to 12 years old, replacement usually makes more sense than a repair. Ask a plumber to quote both, and ask about the energy efficiency of a new unit.

When to call a professional

Call a licensed plumber or electrician if:

• The heater leaks, or you see rust at the base or around fittings.
• Hot water is lukewarm after you check the thermostat.
• You smell gas, or the pilot will not stay lit. See a pilot that will not stay lit.
• The breaker trips, or wiring looks burned.
• The water smells like rotten eggs, which is a different problem covered in water that smells like rotten eggs.
• The tank is 10 to 12 years old and failing.

What not to do

• Do not turn the thermostat up high to get more hot water. It raises the scald risk.
• Do not open an electric heater's panel with the power on.
• Do not ignore a leak around the tank.
• Do not drain the tank without cutting power or gas first.

Bottom line

If hot water suddenly runs out in minutes, suspect a failed lower element on an electric heater or a broken dip tube. If it has been fading for months, think sediment and age. Winter makes everything worse, because the incoming water is colder. When your hot water is not working at all in the cold, see hot water not working in cold weather.