Why Water Heater Not Heating Well? – Troubleshooting Guide

Imagine having to take a cold shower during winter or trying to get rid of the grime on a frying pan with lukewarm water. Water heaters are undoubtedly useful for these sorts of things, but what happens when they fail to produce hot water?

Causes of your water heater not heating well range from something as simple as excessive hot water consumption to a faulty pressure relief valve. An accumulation of water sediments can also keep the heater from increasing the water temperature. The good news is these issues are easily fixed.

A faulty water heater can give you a hot head rather than hot water, so read on to know what could be wrong. This article will go into common causes a heater fails to heat water and what needs to be done to fix them.  

1. Sediment Buildup in the Tank

A build-up of sediment at the bottom of the tank can affect your water heater’s ability to raise water temperature.  

The water that comes out of faucets usually contains minerals like calcium and magnesium. As water is heated, the minerals become sediment particles and end up on the bottom of the water tank.  

When a significant amount of water sediments surround the heating element, it becomes harder for the heater to increase the water temperature. Because they cover up the heating element, the sediment particles end up preventing the heat from being transferred to the water.  

Aside from the water staying lukewarm, rising energy bills and weird popping noises from the tank may indicate that you have a significant build-up of water sediments. You should address this issue before it causes more serious problems such as drain valves and water line clogs.  

Read: How To Keep Your Water Heater From Freezing?

How To Fix?

The quickest fix for a water sediment build-up is to drain the tank, but you may want to invest in a water softener to avoid future problems.  

Below are the steps for cleaning the water tank of your heater.  

  1. Turn off your heat source by moving the temperature setting to PILOT or VACATION mode. For electric heaters, shut power off by flipping the breaker.
  2. Turn your cold water supply valve off.
  3. Allow several hours for the water in the tank to cool down.
  4. Connect a garden hose to the drain spigot of your water heater and place them under the end of the hose in the bathtub or floor drain.
  5. Let air into the tank by opening a hot water faucet.
  6. Open the valve near the drain hose to release water from the tank.
  7. If you don’t hear water draining, you may have to open your water tank’s pressure relief valve to let more air into the tank. 
  8. Open the cold water supply valve to let cold water agitate the sediments at the bottom of the tank.
  9. Inspect the water coming out at the end of the hose and keep flushing the water until it’s clear of sediment particles.
  10. Once the water coming out of the hose is clear, close the valve near the drain hose.
  11. Remove the hose from the drain spigot.
  12. Refill the water tank by opening the water inlet valve on top of it.
  13. Keep the pressure relief valve open to let the air out but close it before the water reaches it.
  14. Restore heat by adjusting the thermostat to your desired temperature or turning the power back on through the breaker.

The YouTube video below gives a full demonstration of how to flush a water heater tank to remove sediment.

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You should flush your water heater tank once every six months to prevent the accumulation of water sediments. As I’ve mentioned, a good option is to install a water softener to reduce calcium and limescale buildup.  

I like Morton Salt’s System Saver II Waer Softener Pellets that you can buy on Amazon.com. It meets NSF and ANSI/AWWA B200 standards, meaning it’s safe not only for your faucet but also for the environment. If you use it regularly and properly, your water tank may be able to last longer.

Read: Why Gas Water Heater Not Working After Power Outage – Troubleshooting Guide

2. Pressure Relief Valve Is Broken

A faulty pressure relief valve can also prevent you from getting hot water. The pressure relief valve can get stuck when it needs to open or fails to close fully. If it stays open, it will cause the water to leak, and the water in the tank won’t remain stagnant long enough to reach your desired temperature.  

As your heater increases the temperature of the water in the tank, the water expands and builds pressure.  

The pressure relief valve is designed to maintain water pressure and release steam and hot water when the pressure reaches 150 psi. Once the pressure is safe, the valve will close again.  

If the pressure valve remains shut, overpressure may cause the tank to leak or burst.  

A pressure valve that gets stuck in the open or closed position must be fixed. Otherwise, it will either keep your water from getting hot or fail to release pressure when needed.   

Aside from the valve getting stuck in the open or closed position, it could also leak from where it’s threaded into the tank.  

Read: Why Does A Gas Water Heater Make A Knocking Noise?

How To Fix?

You can manually open and close the pressure relief valve to unstick it. Open and close it numerous times to ensure it will work as needed. If the valve fails to budge or requires excessive force to open and close, you should replace it.  

Here are the steps for replacing the pressure relief valve:

  1. Shut off the cold water supply.
  2. Turn the heater off.
  3. Allow a few hours for the water to cool down.
  4. Drain enough water from the tank so that the water level is below the pressure relief valve.
  5. Remove the pipe from the pressure relief valve.
  6. Use a pipe wrench to turn the pressure relief tube counter-clockwise to remove it.
  7. Buy a replacement part that’s the same as (or as similar as possible to) the old one.
  8. Apply plumber’s tape around the thread before installing the replacement part.
  9. Use the pipe wrench to tighten the pressure valve tube, but make sure it’s facing down.
  10. Reattach the pipe.
  11. Close the drain of the water tank.
  12. Restore the tank’s water supply.
  13. Turn the heater back on.

The YouTube video below gives a full demonstration of how to replace a pressure relief valve.

If your pressure relief valve isn’t stuck but is leaking from the tank’s threaded opening, removing it and applying the plumber’s tape before threading it back might be able to solve the problem. However, if it continues to leak, you may have to replace the pressure relief valve.

Read: Water Heater Trips Breaker After A Few Minutes – Troubleshooting Guide

3. Excessive Hot Water Consumption

The size of your water heater should be proportional to your household’s water consumption. If you find yourself running out of hot water after someone else uses the shower, or when another hot water appliance is in use, your water heater may be too small.

In a conventional storage water heater, the tank is replenished with cold water heated at the bottom as the water is consumed. If the water consumption exceeds what the heater can supply, the water will not reach the desired temperature.  

Read: Gas Water Heater Not Maintaining Temperature

How To Fix?

One way to deal with an insufficient water heater is to space out consumption by not using hot water appliances simultaneously or in quick succession. Otherwise, the only option is to upgrade your water heater.

You can either get a bigger water heater or a tankless one. Tankless water heaters can give you hot water on demand, but you also need to ensure it’s big enough for your household needs.

Final Thoughts

Water heaters can last well over a decade with proper care and maintenance, but minor faults are sometimes inevitable throughout their lifetime.

Fortunately, most of the issues that keep a water heater from giving you the hot water you need can easily be fixed without seeking professional help.