What to Do if your Water Heater is Not Heating: DIY Repair Tips

Fix a water heater that is not workingImage by Steve Buissinne from Pixabay

You turn on your shower, and there's no hot water. It's barely warm, which is the last thing that any of us want when trying to get ready for work. Why my water heater is not heating? Is it dead? Is it serious, and do I need a plumber?

It's a real pain in the backside, and a cold shower always happens when you least need it, which is anytime, really if we are honest!

The good news is that the possible list of 'suspects' when water heater is not heating is short, so with a bit of troubleshooting knowledge, it should be relatively easy to find the fault and fix the water heater. You can probably repair your water heater quickly without even having to call a technician just yet – that time may come, but for now, let's run through a few obvious things first and see if we can fix the problem.

Ready? Let's get started and see why your water heater is not heating correctly or fully.

Important note: With anything electrical, always ensure the power is off at the breaker before working on your gas or electric water heater.

Water heater is not heating: 7 Common problems and a troubleshooting checklist

Either you are the owner of an electric or gas water heater, below is the list of the common reasons why your water heater is not heating the water:

  1. Electrical supply disruption
  2. Low gas flow (pressure)
  3. Pilot light malfunction
  4. Reset button tripped
  5. Broken heating elements
  6. Faulty thermostat
  7. Bad ECO

Check your electrical supply

If your water heater is not heating, the first thing you need to check is your power supply. Was there a power cut in the night that caused a breaker to pop? If so, that's an easy fix.

Is the water heater switched on?

Perhaps someone in the house has switched it off and forgotten to put it back on.

Why anyone would do that is a complete mystery; however, you can deal with them later. The priority is to get hot water flowing again fast.

Do you have a timer fitted to your system?

If you do, has it been switched off or changed? Could it be a blown fuse or tripped breaker? You can easily change the fuse or reset the breaker, but if that doesn't work and it blows again, call an electrician.

So, if the circuit breaker has tripped, and you want to reset it, simply flip it to OFF then to ON position.

Repair your low gas flow

If you have a gas-fired water heater, make sure your gas is on and you have a good flow (pressure) of gas. You can call your local gas provider to see if there are any current local issues. If the gas pressure is low, it could cause your heater to shut down. If you use propane, check if your tank is empty or low.

Pilot light malfunction

Is your pilot light lit? If it's burning, but there are no flames in the burner, it could be the reset button that has tripped. If the pilot is off, try relighting it, using the correct procedure, and if it doesn't stay lit, then it could be a faulty thermocouple.

They are there to detect the pilot flame, and if the pilot goes out for any reason, the thermocouple will shut off the gas supply for safety. They are inexpensive and easy to replace.

Alternatively, your gas water heater may have an electronic ignition which is more energy-efficient than a permanently lit pilot light. They operate electronically, only when the heat is required. One type uses a small spark like a lighter to ignite the burners, and the other uses an electrically powered hot metal system like a lightbulb filament.

Unfortunately, these units won't last as long as your heater, so they will fail at some point and usually require professional help to diagnose and replace.

Reset button tripped

Check the reset button hasn't tripped out. With the power off, remove the cover panel to uncover the thermostat and the reset button, which is usually red. If it has tripped out, push it back in, and you should hear a definite click. Cover it back up and turn the power on. If your water heater fires up, give it some time to check it's working correctly, and you are all set.

The reset button can sometimes trip following a power surge, a faulty heating element, defective thermostat, or energy cut-off (ECO) switch. If it trips again straight away, you will have to locate the failed component and repair or replace it.

Heating elements (electric water heaters) broken

If your water is very cool, the chances are that both of your heating elements have blown and will need to be replaced. However, if the water is warm but not hot, it may be a single element only that has failed. It's not common for both elements to fail at the same moment, but it does happen. More likely, you will have one fail, followed by the second one shortly afterward. It may be worth changing out both and keeping the used and still-serviceable one as a backup spare.

Thermostat failure

A faulty thermostat is the most common reason for no hot water. They are easy to replace and don't require draining the tank. An electric water heater will typically have two thermostats, one on the top element and the other on the lower one. Upper and lower thermostats are different, so make sure you buy the correct ones by checking the manufacturer's handbook or online at their website.

In a gas-fired water heater, the thermostat is part of the gas valve unit, and if it fails, then the whole gas valve will have to be replaced. This doesn't require emptying the tank, but it may be a job you'll ask your local professional plumber to do for you.

 Energy Cut Off Switch (ECO) fails

Occasionally in a gas water heater, the energy cut-off (ECO) switch will fail. These are designed to monitor the heater's temperature and shut it off to protect your system from overheating and perhaps triggering a fire or other damage. When they fail, they stop the heater from coming on or do so intermittently. The ECO is part of the gas valve, which means replacing the whole gas valve if it fails.


If you managed to locate the fault and get your water heater back up and running again – well done, it's a great feeling, and you've saved yourself some money!

However, for serious issues involving electricity or gas, it's best to call a professional, but at least by reading this short piece, you will now be able to talk knowledgeably about your water heater when the plumber arrives. Knowing how to describe the problem is important as it will save you time and money.

You may have a range of tools that you keep for odd jobs around your home, but an excellent addition to your kit (if you don't already own one) is a multi-meter or multi-tester. This inexpensive, handy piece of equipment will save you time and money by quickly identifying whether a component is faulty or not.

There are many excellent instructional videos online that will run through the basics and help you master these essential instruments.

Hopefully, your troubleshooting skills won't be needed very often, especially if you give your water heater some regular care and attention. The better you care for it, the longer it will serve you without any issues, so you can be confident in getting hot water every time you need it!

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