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8 Reasons Your Hot Water Heater is Only Lukewarm

Water Coming Out of Tap

While it certainly is disappointing to hop in the shower, fully expecting a comforting cascade of hot water, only to be greeted with a pour of lukewarm water, this is actually a pretty common issue in many homes. 

If your hot water heater is only lukewarm—a new hot water heater that’s only lukewarm—there are a few possibilities behind this maintenance issue.

Showering, washing dishes, doing laundry, and plenty of other household tasks and chores can’t be done as well with lukewarm water. 

Here are a few possible reasons why your hot water heater has lukewarm water only so you can get back to steaming hot water fast.

Causes of a Lukewarm Hot Water HeaterResidential Water Heater

If your hot water heater has only lukewarm water, the problem could be caused by one of the following issues:

  1. Sediment build-up
  2. Thermostat is broken
  3. Gas hot water heater is out of fuel
  4. Electric hot water heater doesn’t have power
  5. Broken dip tube
  6. Depleted hot water supply
  7. Clogged pipe
  8. Faulty heating system

Keep reading to learn more about why your hot water heater has lukewarm water only, how to fix the issue, and hopefully how to keep the problem from happening again in the future.

1. Sediment Build-Up

If you realize the water coming from your hot water heater is only lukewarm, it’s likely due to sediment build-up somewhere in your unit. 

Now, if your new hot water heater is only lukewarm, then it may not have been used enough yet for sediment build-up—but if the unit isn’t new, sediment build-up is the most common cause.

As water collects inside your hot water heater to be heated, it’s common for debris in the water—like sand, dirt, and minerals—to settle at the bottom of the tank. 

As the particles collect on the bottom of the tank, the water heater can’t effectively heat your water, resulting in lukewarm water only.

To resolve this issue, open the drain valve on your water heater and see if there is sediment. The water will not be clear if there is sediment build-up. Half-fill the tank with cold water to help loosen up the rest of the sediment, and then drain the tank again. 

Repeat until the water flushes out clear. A better water filtration system can help prevent sediment-build up in your hot water tank.

2. Thermostat is Broken

Another common reason your hot water heater is only lukewarm is because of a broken thermostat. 

If the thermostat on your hot water heater cannot read the temperature correctly, it will heat water to an incorrect temperature and result in you only getting lukewarm water.

Water Heater in Home

To test if the thermostat is broken, turn it to a higher temperature and see if the heater turns on. If it doesn’t respond to the higher temperature and begin heating, then there is likely a problem with the thermostat. 

Generally, this only happens to older hot water heaters, but it can happen in a new one if regular maintenance isn’t performed on your unit (a broken or incorrectly set thermostat could also cause your hot water heater to overheat).

To fix this issue, you’ll need to get the thermostat replaced. To prevent it from happening, be sure you get your hot water heater serviced by a professional at least once per year.

3. Gas Hot Water Heater is Out of Fuel

If the gas is shut off in your home—or if your gas supply runs out—then a gas hot water heater won’t be able to operate, thereby cooling the water inside your hot water tank. 

Check your gas supply if you think this may be the issue. If you have plenty of fuel, then check to see if your hot water heater is getting any of that fuel. 

The pilot light on your hot water heater should indicate if it’s getting fuel or not.

4. Electric Hot Water Heater Doesn’t Have Power

If your electric hot water heater is only lukewarm, then it’s obviously not due to a gas issue. It could, however, be due to a power issue. In most cases, this is because the power source has been cut, most commonly because of a tripped breaker. 

Fix this issue by flipping the appropriate breaker back to “On.” 

Depending on how long the hot water heater has been off, it could take a little while to fully heat the water, but your hot water heater should kick back up again and start heating your water like normal. 

If your hot water heater doesn’t start up again or if the breaker keeps getting tripped, there is likely an electrical problem with your unit that needs to be addressed. Call in a professional to repair the issue.

5. Broken Dip Tube

A dip tube is attached inside your hot water heater, and it directs cold water into the tank from the top, then down to the bottom where the hot water heater warms it up. 

Water From Tap

A broken dip tube can lead to issues with your hot water supply since it can’t properly direct water to the bottom of the tank.

If this is the case, the dip tube will need to be replaced. Unfortunately, replacing the dip tube isn’t always worthwhile, and it may be more cost-effective to replace the entire hot water heater

Getting your hot water heater serviced regularly can help prevent the dip tube from breaking, but often it breaks simply after years of regular use. 

6. Depleted Hot Water Supply

Hot water heaters typically have a tank where they keep hot water until the water is used. If it seems like your hot water heater has only lukewarm water, it might be that you’ve depleted your supply of hot water and your hot water heater needs some time to heat up more.

To prevent this from happening, you can get a larger hot water heater tank or stagger the use of hot water in your home. 

Try scheduling showers at different times, and be mindful when you run appliances that use a lot of hot water (such as the dishwasher and washing machine).

7. Clogged Pipe

Sometimes a supply of lukewarm water isn’t the fault of your hot water heater, but rather an issue with your pipes. 

If you have a clogged pipe, something could be preventing hot water from making its way to your faucet. Check your water supply in different sinks and showers to see if they all are dealing with a hot water shortage or if it’s just one of them. 

Bryant Water Heater

If it’s just one, consult with a plumber to help identify the source of the clog. Once the source has been identified, a plumber can help you figure out if the pipe needs to be replaced or simply cleaned. 

8. Faulty Heating System

In some cases, a hot water heater has lukewarm water only because the heating system itself is faulty. If this is true for your hot water heater, there, unfortunately, isn’t much you can do to fix the issue or prevent it from happening in the future. 

A broken hot water heater will need to be replaced altogether.

Schedule Your Hot Water Heater Service Appointment Today

Preventative maintenance is one of the best ways to keep your hot water heater working optimally. Don’t settle for a hot water heater with lukewarm water only

Keep your unit tuned up and your hot water supply full by working with our expert team at John C. Flood. Schedule your service today.