Why Is My Hot Water Heater Only Lukewarm? Common Fixes

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Imagine choosing to take a hot shower to combat the chill of a cold winter’s day, only to be greeted by icy water where hot water should be flowing. Or, even worse, water that is almost warm. What you expected, is not what you’re getting from your shower, which leaves you frustrated and shivering.

As another example, you might want to wash many dishes thoroughly using hot water, but only tepid water comes out. The lack of hot water may force you to abandon your dish-washing task, potentially derailing other chores or dinner plans. 

In many cases like the ones listed above, your water heater might be showing signs of malfunction, rendering your bathroom, or any other faucet, useless. Luckily, it is possible to diagnose and fix the issue of lukewarm water. If you are quick to fix the issue, it can also prevent future problems from occurring with respect to your heater.

So, in this article, we are going to explore the common causes of lukewarm water and discuss how you can troubleshoot with your water heater to fix the issue. There are DIY solutions and professional options available, which we will outline for you, helping you discern when you might need to dial for help.

Let’s begin!

Hot Water Heater Only Lukewarm

Reasons Why Your Hot Water Heater is Only Lukewarm 

If the water flowing from a previously hot tap is lukewarm, it doesn’t necessarily mean that the water isn’t heating. Occasionally, a specific malfunction can occur and prevent water from heating before it exits the faucet.

In other cases, it is also possible that the water in your heater is mixed, making the cold water run before the heated water. However, it is important to note that the issue may also not be related to the heater itself, which points toward concerns relating to piping or the entire heating system.

Thermostat Issues

​If you have a water-based heater, your problem may lie with the thermostats. Typical heaters have two cylinder thermostats, located in different areas on the heater, depending on the manufacturer. Be sure to check both of the thermostats, since failure of just one can cause lukewarm water to flow from a hot water tap.

Another thermostat malfunction that can occur is an issue with the measurement system, which involves a thermostat showing the wrong temperature and causing the cylinder to cease warming before an optimal temperature has been reached. 

A third potential issue with a heater thermostat is incorrect thermostat settings. Check to ensure your thermostat is calibrated to sense the right temperature, and adjust as needed. Otherwise, it may need to be replaced, which can be done by a professional.

Heating Element Problems (Electric Heaters) 

It is possible to experience an element issue with electric heaters. For instance, a heater’s breaker may be tripped, which means that the circuit breaker connected to the heater may have been overloaded or have experienced a fault.

It is important to note that, with some cylinder types, the water warmed inside may remain lukewarm for days before it becomes cold. If the breaker was tripped, and the heater stopped working, that might be the reason for the lukewarm water flowing. In this case return the breaker to its position and check to see if the heater has started warming the water again. 

Sediment Buildup

Elemental wear and tear or sediment buildup can impact the function of a heater, resulting in lukewarm water. Over time, minerals like calcium can accumulate, especially in areas with hard water. 

The mineral buildup can act as an insulating barrier, resulting in the heating element being blocked and unable to heat water. Alternatively, the lower element can overheat in this case, and burn out. Therefore, regular flushing of the tank is a must to prevent this issue.

Dip Tube Malfunction 

This is potentially the most catastrophic cause of lukewarm water flow. The dip tube regulates water flow in a heater, making sure that the cold water, located at the bottom of the tank, is heated. A broken or misplaced dip tube can lead to cold water mixing with hot water, resulting in lukewarm output.

If for some reason it stops functioning as expected, the cold water will remain on the top of the tank, that way exiting the tank before the hot water, so you will always get lukewarm water when using the hot water tap. This malfunction can cost you the entire tank, so it is important to root out this issue as soon as possible. 

Gas Supply Issues (Gas Heaters) 

In terms of water heaters, problems with the gas supply can be caused by low gas pressure, a clogged gas line, or burner issues. If the gas pressure is too low, heating may become an issue. Similarly, a clogged gas line can prevent flow, resulting in lower heating output. Finally, burners can be damaged or clogged, which can prevent them from providing adequate heat, resulting in lukewarm water. 

Leaks in the Tank or Plumbing

If there are leaks in the tank or plumbing (connected pipes), water temperature can be significantly impacted. For instance, this can lead to the escape of heat through disconnections or openings. Also, pressure drops can reduce flow rates, ultimately slowing or stopping the heating process. If you suspect a leak, it’s important to inspect the system and be open to calling a professional for review.

Corroded Anode Rod 

The anode rod of a water heater reduces corrosion inside the tank through rusting. A corroded anode rod can lead to tank damage, reducing the lifespan of the tank itself and leading to the need for replacement. Additionally, heating efficiency may be lost if an anode rod is corroded, which can lead directly to lukewarm water output.

Overuse or High Demand

We understand that hot water is a precious resource, but it is essential to avoid using too much hot water at once, or running multiple hot water sources simultaneously. This can strain your heater, which may lead to lukewarm water due to increased recovery time and reduced flow rate. If this is a consistent issue, it may be time to upgrade to a larger water heater to meet your household’s needs.

Aging Water Heater

Lastly, water heaters do not last forever. Aging units, such as traditional units that are 10-15 years old, or tankless units that are over 20 years old, will lose efficiency over time. The components of these units, such as insulation, thermostats, and more can degrade and minimize heating efficiency. Also, as technology improves, heaters compete less and less with current models.

How to Fix Lukewarm Water Issues

Lukewarm water issues can be solved one of two ways: either through your efforts or by calling a professional. Hopefully, the guide below will help you decide which of the two solution types works for your lukewarm water concerns.

water-heater-gas-vs-electric

DIY Solutions 

DIY solutions are perfect for individuals that would like to fix their heater themselves, or if the problem is on the smaller side. Here are a few scenarios where you may be able to fix your heater without assistance. 

  • Check and Adjust Thermostat: The thermostat is usually found behind an access panel close to the bottom of the tank. If you own a tankless heater, the thermostat might be on the unit’s control panel. Take a flathead screwdriver and adjust the setting to between 120-130 Fahrenheit. 
  • Flush the Tank: To flush the water heater, begin by turning it off, then connect a garden hose to the drain valve at the bottom of the tank. Next, turn off the cold water supply and open the drain valve. Once the tank is empty, turn the cold water supply back on to flush out any sediment. Upon finishing, close the drain valve and begin refilling the tank.
  • Test Heating Element (Electric Heaters): To check if your heating element is working well, you may need to grab a multimeter. First, to use the multimeter, turn off power at the circuit breaker and access the heating element. Make sure that you disconnect wires as needed. Then, set your multimeter to the ohms setting and check if a reading between 10-30 ohms is achieved, indicating a well-working machine. 
  • Relight Pilot Light (Gas Heaters): Relighting the pilot light involves turning off the gas and turning the pilot control knob to the “pilot” position. Once that is done, use a long or barbecue lighter to ignite near the pilot while pressing the reset button.
  • Check Power Supply: To do this, you should inspect the circuit breaker. The circuit breaker can be reset by flipping it on and off. Also, check the power cord and test the outlet if needed.
  • Inspect for Leaks: Lastly, you can inspect for leaks by examining the tank, double-checking connections, and look for errant drips on the drain valve. 

Professional Solutions

If you cannot solve the heater issue on your own, or if you want a professional to lay eyes on the problem, here are some scenarios where your efforts may not be enough to salvage the issue.

  • Replace Heating Element or Thermostat: If you have tested your heating element or thermostat and have noticed faults, you may need to call a professional due to the complexity of the issue. 
  • Repair or Replace Dip Tube: If you need your dip tube replaced, call a professional. Professionals know how to replace it without damaging your appliance, and can provide expert advice on how extensive the repair needs to be.
  • Address Gas Supply Problems: Gas supply problems should always be addressed by a professional, as they know how to handle the issues safely. Also these professionals are trained to handle gas systems according to local codes and regulations in a compliant manner. 
  • Repair Leaks: Leaks need professional repair, especially if the tank needs to be replaced, as water damage can be extensive if not handled properly.
  • Replace Anode Rod: If you need to replace your anode rod, professionals have specific tools for this job that give them superior access. Also, it is safer to have a trained professional come and make their assessment. 
  • Clear Blockages: Similar to the anode rod, plumbers have specialized tools, such as augers that effectively clear tough blockages without damaging the surrounding pipes. 
  • Replace Water Heater: In general, replacing a water heater should be left up to the professionals. If your heater is older than 10 or 15 years, it may be inefficient and need replacement. 

Preventive Measures

If you have fixed your heater and want to make sure an issue like this does not arise for a long time, preventative maintenance is key. Here are a few things that you can do to protect your heater.

Regular Maintenance

Many people do not know this, but it is a good idea to flush your heater annually to prevent sediment buildup. While you’re there, check the thermostat to ensure it is working well, and replace your anode rod if it is becoming corroded (every 3-5 years.)

Consider Upgrading

Have you thought about upgrading to a larger or more efficient water heater? It may be time to do so, especially if high demand or aging is an ongoing concern. 

Insulate Pipes

Pipe insulation can help reduce heat loss and maintain water temperature. If the heat cannot escape, it will be funneled right to your faucet, leading to warm showers and hot dishwashing water. 

Address Hard Water Issues

You are encouraged to use water softening solutions to prevent sediment buildup from hard water and to extend the heater’s lifespan. Check the hardness of your local water to determine how frequently to use water softeners.

Conclusion

If your water flow is producing lukewarm water output, we hope that this guide puts your mind at ease. It is important to maintain hot water in your home for daily comfort and convenience, and this is possible with the solutions we have provided above. 

Try DIY solutions first, but seek professional plumber’s help with your water heater when necessary. Regular maintenance and performing preventative maintenance can help you to avoid future issues. 

Marco
Marco
Meet Marco, a lifelong tinkerer and DIY enthusiast, developed a passion for plumbing after fixing a leaky faucet in his own home. Years later, he turned that passion into a thriving business, Amarco Plumbing, where he shares his knowledge and expertise with the community.