Why is my tankless water heater not getting hot enough

February 22, 2019

You use hot water every single day in your home. That’s great, until the hot water starts turning lukewarm and then cold.

If your water heater isn’t producing enough hot water for you, it can ruin your shower and make it difficult to clean dishes and laundry.

To figure out why you aren’t getting enough hot water, let’s go over the 5 most common reasons and how you can fix them.

Sediment or Rust

Over time, especially if you have hard water, minerals in the water can gather at the bottom of the water heater near the burner. This sediment can prevent heat from the burner from reaching the water, compromising energy efficiency and your access to hot water.

A water softening system can help slow this process down, but you can probably eliminate this problem by draining your tank once a year. Schedule professional water heater maintenance and your technician will drain the water heater for you.

If there is rust, you may need to replace your water heater. Don’t wait for the tank to burst. Contact a qualified professional if you notice rust around your unit and start looking for replacements.

Thermostat

There is a thermostat inside your water heater that tells it when to turn on and heat more water. If it has malfunctioned, it is probably telling the water heater not to turn on because it thinks that the water is hot enough. If this is the case, you may need to replace the thermostat.

If your water heater thermostat is working, raising the thermostat temperature can help get the water hotter, but don’t go above 140 degrees. This could create scalding water. Some thermostats don’t have degrees, but rather “warm,” “hot,” and “very hot” settings. For an accurate temperature reading, use a thermometer to measure the temperature of the water coming out of your hot water tap.

One possible solution is installing a thermostatic mixing valve, otherwise known as a tempering valve or anti-scald valve. This mixes cold water with hot water as it comes out of your tank, allowing you to raise the water heater temperature and get more hot water without the risk of scalding.

Wrong-Sized Water Heater

Another reason for insufficient hot water is that your water heater might not be big enough for your home. If you’ve just moved into a new home, or if you installed a new water heater yourself, this could be the case. Consult a professional contractor to help you correctly size a new water heater and install it for you.

If you want never-ending hot water, consider a tankless water heater, also known as instantaneous or on-demand water heaters. Instead of storing hot water in a tank, tankless units heat water directly as it moves through the unit. This not only saves space, but energy as well. According to the U.S. Energy Department, “demand water heaters can be 24%–34% more energy efficient than conventional storage tank water heaters.”

Traditional tank water heaters last around 10 years whereas tankless water heater last around 15-20 years. If you are considering a new water heater, speak with the professional at Service Champions.

The Dip Tube

To supply your water heater tank with new water, a plastic tube is installed inside the tank that runs all the way to the bottom. This keeps the cold water from mixing with the hot water.

If the dip tube breaks, cracks or falls off, it could cause cold water to mix with the heated water at the top of the tank. Instead of hot water, you could be receiving tepid water instead. Contact a professional if you suspect a defective dip tube.

Too Much Demand at One Time

If you are running the dishwasher, washing machine, and shower at the same time, even a large tank will struggle to provide all the hot water you are demanding. Try to run the dishwasher and washing machine at times when people won’t be taking hot showers or baths.

Flow rates could also present a problem. By installing low-flow faucets and showerheads, you can reduce the gpm (gallons per minute), thus increasing the amount of hot water you get for each hot water tap. Aim for 2.5 gpm or less.

If your Northern California home still isn’t receiving enough hot water, you may have an issue with your burner or some other part. Contact the trusted water heater experts at Service Champions to bring the heat.

Lukewarm water is unpleasant in the shower and ineffective for thoroughly cleaning clothes, dishes, and other items that need to be regularly washed in warm or hot water. It's important to fix this problem and regain the hot water that you were once able to enjoy. Addressing a water temperature issue doesn't just improve your relaxation in the shower: It's also necessary to ensure that you have the hot or warm water you need to effectively clean dishes, clothes, and more.

However, if you don't know how to inspect and rectify the problem, you may need to rely on a professional plumber to fix the issue. DIYers that are experienced in plumbing may be able to resolve this issue on their own, though it depends on the exact cause of the problem. Keep reading to find out what to do when your hot water isn't getting hot enough.

Check and Adjust the Thermostat

One of the first things to check if the hot water in your home is now coming out lukewarm, cold, or even if it's too hot is the thermostat on the hot water tank. It may sound like a common-sense solution, but many people don't know that the hot water tank has a thermostat to adjust and it can get bumped or otherwise changed by accident when someone is working in the utility room and around the hot water tank.

Check the thermostat and adjust the temperature if it is too low or too high. Just make sure that you don't set the temperature above 120ºF, as this can lead to scalding temperatures and severe burns.

If you adjust the thermostat and the water temperature remains the same, the problem may be a broken or faulty thermostat. Unfortunately, if this is the problem, then you will need to call a plumber or a hot water tank technician to fix or replace the thermostat.

Tripped Hot Water Tank Breaker

Electric hot water tanks use heating elements that are powered by electricity to heat the water within the tank, but like all electrical appliances, equipment, and fixtures, electric hot water tanks are susceptible to power surges, shorts, and other issues that can cause the breaker to trip. If the water temperature suddenly changes and continues to get colder, then the issue may be caused by a tripped breaker or blown fuse.

Fixing this problem is usually as simple as flipping the breaker back to the ON position or replacing a blown fuse, but if the breaker trips again or the water heater simply doesn't restart, then there is likely a malfunction in the home electrical system or the hot water tank that will need to be fixed by an electrician or a licensed hot water technician.

It should also be noted that if the water remains lukewarm for more than a day, then it's likely that a tripped breaker isn't the problem, as the hot water tank is receiving power and it's still able to partially heat the water.

Unmanageable Hot Water Demand

One of the more common issues that can impact the temperature of the water is the current demand within the household. If you got a burst of energy and put on a load of laundry, filled the dishwasher, then hopped in the shower to relax, then it's likely that the amount of hot water you are attempting to use is more than the hot water tank has stored. If this is a common occurrence in your home, then it may be beneficial to invest in a tankless hot water heater that heats the water on demand.

Also, keep in mind that you will always struggle with hot water issues if the hot water tank is too small for the home. If the hot water tank reliably supplies hot water to the appliances and plumbing fixtures in the home, but the amount of hot water isn't enough to suit the needs of the household, then consider upgrading to a larger hot water tank or replacing the hot water tank with a tankless water heater.

Sediment Build-Up

Homeowners that regularly deal with hard water problems are likely familiar with sediment build-up in the bottom of the hot water tank. Over time, minerals in the water sink to the bottom of the tank and stick to the heating elements, reducing the amount of heat transferred from the heating elements to the water. This sediment impediment can result in the hot water tank running constantly to try and increase the heat of the water, though in many cases the lukewarm water is needed before the hot water heater can adequately heat the water through the sediment.

Resolve this problem by draining and flushing the hot water tank. Experienced DIYers can generally handle this task on their own, but homeowners that lack experience will likely need to call a plumber or a hot water heater technician to resolve this problem. It's advised by Consumer Reports to schedule regular maintenance to help prevent this problem and keep the hot water heater in top working condition.

Leaking Hot Water Tank

A leak from the hot water heater needs to be fixed as soon as possible. Not only can a leak reduce the temperature of the water, but it can also cause severe injury to unsuspecting individuals who may step in or touch the leaking hot water. Leaks in any water system pose a risk to the structure of the home and may cause significant water damage, leading to costly repairs.

If you see or suspect a leak in the hot water heater, turn off the water to the water heater and call a professional plumber or hot water tank technician immediately. Keep in mind that even with the water turned off, there is still an entire tank full of water that can drain through the leak in the tank, so be prepared to catch any water with a bucket and soak up additional water with one or more towels. Just don't make direct contact with the hot water during cleanup to avoid burns.

Damaged or Displaced Dip Tube

Hot water heaters must be supplied with cold water that is then heated. The hot water is drawn from the top of the hot water tank, while the cold water is directed to the bottom of the hot water tank by the dip tube. By carrying the cold water to the bottom of the hot water tank, this allows the cold water to come into contact with the internal heating elements. However, if the dip tube is damaged or displaced, then the cold water may be released at the top of the tank, cooling the hot water to a lukewarm temperature.

Defective dip tubes aren't an issue that can be tackled by most DIYers, so it's advised to contact a plumber or a hot water heater technician to repair or replace the dip tube. Once the hot water heater has a new dip tube, the hot water in the home should return to its standard temperature.

Broken Gas Valve

Gas-powered hot water tanks burn incoming natural gas to heat the water in the tank, similar to the way in which a furnace burns natural gas to heat the air. However, if the hot water has become lukewarm in temperature, then a faulty or broken gas valve could be the culprit, resulting in the tank burning an insubstantial amount of gas to heat the water.

Replacing the gas valve is a task that should only be handled by trained professionals, and it's important to note that if you smell rotten eggs or a strong scent of garbage, then the gas valve is likely leaking. This is an emergency situation. Immediately call the local gas company to shut the gas down and leave the home until it has been deemed safe to return. Not only can natural gas leaks cause fires and explosions, but the gas can also be inhaled. Natural gas isn't visible and it's completely odorless, though gas providers use an additive to create the rotten egg and garbage smell for the purpose of detecting leaks.

Warning

If you suspect a gas leak, leave your home and call the gas company and 911 immediately.

Faulty Heating Element

In the bottom of the hot water heater, there are one or more heating elements that are used to heat the incoming cold water. As mentioned previously, these elements can become covered in sediment, reducing their ability to heat the water. However, even without sediment build-up, the heating elements can become damaged and inefficient after years of regular use.

If a heating element has failed, then the hot water heater won't be able to effectively heat the water, resulting in lukewarm water throughout the home. Contact a plumber or a hot water heater technician to repair or replace the heating elements and restore hot water to the home.

Worn out Water Heater

It's important to note that most hot water tanks last only about 8 to 12 years on average, so if your hot water heater is nearing this age, you could experience a range of problems, like faulty heating elements, broken gas valves, a damaged dip tube, or even a problem with the thermostat. While each of these issues can be repaired individually, ongoing problems with the hot water tank may be a sign that the entire unit needs to be replaced.

In this situation, you will need to hire a professional plumber or hot water tank technician to replace the hot water heater. Consider upgrading to an energy-efficient tankless water heater that heats the water on demand. These tankless units last about 15 to 20 years, making them a great investment for a new home and ridding you of most lukewarm water problems.

Why is my tankless water heater only lukewarm?

What is the most common problems with tankless water heaters?

Why do I suddenly have less hot water?