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Home » Water Heaters » Common Water Heater Problem Troubleshooting Guide

Common Water Heater Problem Troubleshooting Guide

By: David Trinh
Last Updated:
troubleshooting guide

A failed water heater is every homeowner’s worst nightmare. Whether your heater stops producing hot water, the water pressure drops, or the tank starts leaking, the problem makes your life uncomfortable and difficult.

Instead of calling a plumber or just giving up on your water heater and buying a new one, try troubleshooting the issue yourself. There’s a good chance it’s something simple that you can fix on your own.

Tank Water Heater Problems

Tank hot water heater not working? The problem could be down to something different according to whether it’s an electric or gas water tank not heating.

Tank Electric Water Heater Troubleshooting


Check out the list below of the most common electric tank water heater problems to find your issue. Before attempting to fix anything, always turn off the water heater at the service panel and then check the wires in your heater using a non-contact voltage tester — this will ensure that the heater really is off.

1. Leaking from the Top

It is important to fix a leak (even a minor leak) as soon as possible to prevent damage to your home or the water heater itself, including a short circuit. The leak could be coming from:

  • The ball valve. This inline valve is a joint with a handle. Stop the leak by tightening the nut that is holding the handle in place.
  • The pressure relief valve. The best thing to do when a T&P valve is leaking is replace the valve entirely.
  • A loose connection or stripped threaded nipple. If neither of the above are the problem, this is most likely the cause. A loose connection or stripped threaded nipple is a more difficult problem to resolve yourself — you’ll probably require a plumber.

2. Leaking from the Bottom

There are also several potential causes for water leaking from the bottom of your heater:

  • The drain valve. Check that the valve is completely closed. If it is, the leak is a sign you need to replace it.
  • The pressure release valve. Although the T&P valve is located at the top of the heater, a leak may appear at the bottom. This happens when the water is exiting through the overflow tube. You’ll need to replace the valve to resolve the problem.
  • Condensation. If neither of the above are the issue, the leak could be due to condensation. Check if this is the case by turning off your heater for a few hours to see if the leak stops. If it does, turn down the thermostat to prevent more condensation in the future.
  • The tank itself. If none of the above stop the leak, your tank itself may be leaking. This means that your water heater has come to the end of its life and needs replacing.

3. No Hot Water

If you’re receiving no hot water at all from your heater, it may lack sufficient power, have a tripped limit switch, or have a failed heating element. You’ll need to troubleshoot these one by one to diagnose the problem. The first thing to check is the circuit breaker for the water heater. If the breaker is tripped, simply switch it off and then on again. If the breaker is not tripped, move on to checking the high-temperature limit. Locate the access panel for the upper heating element and remove it. Next, carefully remove the insulation and plastic safety guard. After you’ve done this, press the high-temperature cutoff reset button. This is a red button above the upper thermostat. Put everything back and turn the circuit breaker on.

If you’re still without hot water after resetting the high-temperature limit, the problem must be in one of the heating elements. You’ll need to test each until you find where the problem lies. Bear in mind that more than one may have failed. Touch each screw with a tester probe. A heating element that doesn’t light up the tester needs replacing.

4. Insufficient Hot Water

A failed heating element can also lead to insufficient hot water. If your heating elements are fine, you may be able to increase the amount of hot water you receive by raising the thermostats. Remove both side panels covering the thermostats and the insulation beneath. Adjust the temperature using a flathead screwdriver.

If your thermostats are already set to a high temperature, the problem could be that your tank is too small to provide you with all the hot water you need. This especially likely if you now require more hot water than you used to. In the case that none of these are the cause, insufficient hot water is likely due to a damaged dip tube — the part of the heater that takes the cold water from the inlet down into the unit. Drain the tank and install a new dip tube.

5. Water Is Too Hot

When water is too hot, the problem is usually that the thermostats are set too high. If you live in an area of extreme temperatures, remember to lower the thermostats as soon as the warm weather begins. If you find that the thermostats are already set to a reasonable temperature, check that they are working by testing for continuity with a multimeter.

6. Water Takes Too Long to Reheat

Electric tank heaters can take a while to reheat water — this is just a downside of the design, as opposed to a problem that needs to be fixed. However, if your heater starts taking longer to reheat water than it used to, you should check the condition of the heating elements and thermostats. One or the other may need replacing. Check heating elements with a testing probe and thermostats with a multimeter.

7. Low Hot Water Pressure

If your water pressure has dropped recently, it may be time to clean your tank of sediment and calcium deposits. Do this by following these steps:

  1. Turn off the cold water supply to your water heater.
  2. Open a hot water faucet anywhere in your home. This will prevent a vacuum forming in the tank.
  3. Connect a hose to the drain valve at the base of the tank. Leave the end of the hose in a bucket or drain. Open the valve to start draining.
  4. Remove the anode rod at the top of the tank. It may be covered by a lid.
  5. Pour in three to four gallons of vinegar and replace the anode rod.
  6. Turn the water supply back on for just five to 10 minutes and then leave the vinegar in the tank for at least six hours before draining.
  7. Refill your tank and turn the power back on.

You can also increase water pressure to individual appliances by cleaning sink aerators and shower heads. If all this fails to work, the likely culprit is the old ½-inch diameter of your galvanizing piping, which needs updating to modern ¾-inch piping.

8. Strange Noises

It is normal for water heaters to make some noise, but if your tank starts becoming more noisy than usual, it’s a good idea to check for leaks and too much pressure. You may also be able to reduce noises by cleaning your tank (instructions above).

9. Dirty or Rusty-Colored Water

Dirty or rusty water isn’t just unpleasant: it requires immediate attention because it’s a sign that your heater’s anode rod is corroded. Leave the problem any longer and your tank will likely develop a leak. Simply replacing the anode rod will return your water to its natural color and save your tank.

10. Smelly Hot Water

Smelly water can also be a sign of a corroded anode rod. As well as replacing the rod, flush your tank clean (instructions are above).

Tank Gas Water Heater Troubleshooting


Like with an electric tank heater, you need to turn your gas water heater off before troubleshooting. To do this, simply turn the thermostat to the “off” position.

1. Leaking from the Top

The procedure to fix a leak from the top of a gas tank heater is the same as for an electric tank heater. Make sure to keep the cold water inlet turned on until you find the leak. Otherwise, you may end up lowering the water pressure enough to stop the leak — without fixing the problem! If you are unable to find the source of the leak at first, wrap the pipes with tissue paper and wait for damp spots to appear.

2. Leaking from the Bottom

Similarly, the same problems that affect electric heaters can contribute to water leaking from the bottom of a gas water heater. Just make sure that the leak really is coming from the bottom and isn’t water dripping down from the top.

3. No Hot Water

When your gas heater is producing no hot water, the first thing to do is check that the pilot light is on. If it has gone out, follow the instructions on your water heater to relight it. In the case you have electronic ignition, check if the breaker has tripped, turning it off and then on to start it working again.

If the pilot is on but you have no hot water, turn to the thermocouple. This needs to register that the pilot light is on before it will ignite the gas. Try cleaning the thermocouple. If that fails, replace it with a new one.

4. Insufficient Hot Water

Insufficient hot water from a gas tank heater is due to the same issues that impact an electric heater. If you figure out that you simply need to turn up the thermostat in the winter, this requires a different (and much simpler) process than for an electric heater: just turn the knob on the front.

5. Water Is Too Hot

Extremely hot water is dangerous: it can cause scalding or lead to the rupture of your water heater. Use the same troubleshooting methods as for an electric tank heater to resolve this problem.

6. Water Takes Too Long to Reheat

Gas water heaters that are taking longer to reheat often have dirty or clogged burner orifices. Cleaning them will usually do the trick. very corroded yet.

Alternatively, look at whether you need to turn up your gas pressure. The gas pressure rating should be on a label on the side of your water heater.

7. Low Hot Water Pressure

Low hot water pressure in a tank gas heater is due to the same issues as in an electric heater. Clean your tank (the procedure is the same as for an electric heater) and if that doesn’t work, consider upgrading your galvanized pipe.

8. Pilot Not Lighting

If you are unable to light the pilot, you could have an issue with the thermocouple, orifice, tube, or gas valve or there could be air in the gas line. Your best option is to ask your gas utility company to troubleshoot the problem for you. Often, this service is free.

9. Pilot Not Staying Lit

It’s also possible that the pilot is lighting but then going out. This may be due to a faulty thermocouple, which you can test with a multimeter.d yet.

If the thermocouple turns out to be fine, the problem could be a gas valve in poor condition. This is easy to replace yourself. Alternatively, it could be a partially clogged vent, the latter of which a plumber should fix.

10. Burner Not Staying Lit

Another problem is a burner that won’t stay on. Lower and then raise the temperature on the dial while running hot water. If this fails to solve the problem, check the thermocouple, burner orifices, and vent to find the issue, using the instructions above.

11. Strange Noises

Just like with an electric heater, some noises are normal. If the noises your heater is making are different from usual, clean the tank.

12. Rusty-Colored Water

Like with an electric water heater, rusty water signals the need for a new anode rod.

13. Smelly Hot Water

You may be able to eliminate the bad smell in your hot water simply by increasing the temperature on your heater to 140 degrees Fahrenheit. If this fails, clean the tank. If the smell returns, change the anode rod — even in the case it doesn’t look very corroded yet.

Tankless Hot Water Heater Problems

Tankless water heaters experience different problems from their tank counterparts. The good news is that the lack of a tank means that issues are less common. Once again, you will need to troubleshoot according to whether it’s a gas or electric water heater not working.

Tankless Electric Water Heater Troubleshooting


When troubleshooting an electric tankless heater, it is again essential that you have switched off the power in the breaker box and confirmed that all the wires are inactive before you begin.

1. No Hot Water

The most common reason an electric tankless heater stops producing hot water is a worn-out heating element. You can replace the heating element yourself by shutting off the water supply to your heater and draining any water that remains in your heater by turning on a hot water faucet. Next, open the heater by removing the cover, disconnect the wires, and switch out the old heating element for a new one.

2. Insufficient Hot Water

Electric tankless heaters usually only supply a few gallons per minute of hot water. They are unable to provide multiple appliances with hot water at the same time. For this reason, it is important to calculate how much hot water you’ll need when purchasing an electric tankless heater. Bear in mind that incoming water temperature will impact maximum gallons per minute you receive.


If you find that your electric water heater is unable to meet your needs, consider adding a second unit. Electric tankless heaters are more suitable as point-of-use heaters, especially in average to large homes.

3. Water Is Too Hot

Just like with tank heaters, water that is too hot could be because the temperature is set too high. If this is not the case, the likelihood is you need a new thermostat or temperature sensor. Find out if one is not working by using a multimeter.

4. Mineral Buildup

Even though your water heater has no tank, it will still start to suffer from mineral buildup unless you clean it on a regular basis. If you have hard water, this means flushing the heater every six months. Otherwise, once a year is likely enough.

The process is slightly different from cleaning a tank water heater:

  1. Remove the lid.
  2. Close the three water valves.
  3. Remove the purge port valve caps. This will release pressure inside the heater.
  4. Attach a hose to each of the valves and then reopen them.
  5. Wash your water heater with vinegar.
  6. Turn the valves back off, remove the hoses, and replace the caps.
  7. Remove the filter and rinse it with water.
  8. Put everything back together and restart your heater.

5. System Overload

Your unit may shut down if it is overloaded, such as if hot water demands become too high. Simply reset the heater to start it working again.

6. Cold Water Sandwich

A cold water sandwich is when water starts off hot, turns cold for a few seconds, and then returns to the right temperature. Unfortunately, there’s no fix for this — other than choosing a tankless water heater that doesn’t suffer from the problem. When you shower, wait for the water to run cold and become hot again before you enter.

Tankless Gas Water Heater Troubleshooting


Many of the tankless gas water heater problems are the same as those experienced by tankless electric heaters. However, there are a few differences.

1. No Hot Water

First, check that your gas valve is turned on. If it is, the problem could be an obstructed heater vent, which requires professional attention.

2. Insufficient Hot Water

Your tankless gas heater may provide insufficient hot water if it is too small for your needs. Your best option is to switch to a larger unit — you can find gas tankless heaters for all sizes of homes, up to very large. Alternatively, make sure your family uses less appliances simultaneously.

3. Water Is Too Hot

The causes of water that is too hot in a gas tankless heater are the same as for all other types of water heaters. Bear in mind, if the thermostat is working and set correctly, the temperature sensor could be broken or it could just need repositioning.

4. Mineral Buildup

Mineral buildup affects gas tankless heaters just like electric heaters and requires the same cleaning procedure. Again, you’ll need to clean it more often if you live in an area with hard water — i.e. water with high mineral content.

5. System Overload

A system overload can affect gas tankless heaters just like electric heaters. If this problem happens on a regular basis, consider switching to a more powerful heater.

6. Ignition Failure

Many tankless gas heaters let you know if they have an ignition problem by displaying an error message. If this occurs, confirm that your gas tank is full (if you have one) and that the gas valves are fully open. If neither of these is the problem, call a technician.

7. Flame Failure

A flame failure is often due to a blockage in the venting. You’ll need a professional vent cleaning service.

8. Air Supply or Exhaust Blockage

Another error code that can appear on tankless gas heaters is air supply or exhaust blockage. If there are no obvious objects or debris blocking the venting and you are meeting the clearance requirements set out in the heater’s product manual, you’ll need a plumber to inspect the pipes and connections.

9. Cold Water Sandwich

Like electric tankless heaters, gas water heaters can suffer from cold water sandwich. Again, there’s no fix other than changing to a heater designed not to have the problem.

If You Still Can’t Fix Your Heater

There’s always the possibility that your water heater has come to the end of its life and is beyond repair. This is particularly likely to be the case if you have a tank water heater that is more than about a decade old. If you do need a new water heater, consider upgrading to a tankless model — it will save space, reduce energy costs, and last much longer.

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David Trinh
David is an expert in all things plumbing, heating, cooling, and water treatment. He got his start in the plumbing business working on fixing all types of home improvement issues including water leaks, broken toilets, appliance installation, and more. Over time, he learned a ton about installing and choosing the correct water treatment products for homeowners.

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