Why Am I Not Getting Hot Water From My Tankless Hot Water Heater?

Why Am I Not Getting Hot Water From My Tankless Hot Water Heater


Not only are tankless water heaters easy and inexpensive to maintain, but they’re energy-efficient and pretty durable. But this doesn’t mean that a tankless hot water heater will always run smoothly and not encounter any problems.

Common issues that your tankless hot water heater might run into may be a lack of hot water or not igniting at all. 

Tankless water heaters are also known as instantaneous water heaters or demand-type water heaters, because they provide hot water when you want it instantly. Their cost-efficiency is due to the fact that they produce no standby energy like other storage water heaters.

A tankless water heater provides hot water without using a storage tank. But when you turn a hot water tap on, it is cold water that travels through the pipe and into the unit.

The water is then heated by an electric or gas element. With a tankless hot water heater you don’t need to wait for a storage tank to fill with hot water. However, the output of the tankless water heater will limit the flow rate. 

But what do you need to do if your tankless hot water heater isn’t producing hot water, and why might it not be producing hot water in the first place? Let’s take a look at a couple of reasons why this may be happening and how to solve the problem.

Why Is There No Hot Water Coming From My Taps?

No hot water could be coming from your taps for a lot of reasons, and it’s important to consider the following factors.

Running Too Many Appliances

If the shower is being used at the same time as the dishwasher and laundry machine, it’s possible this is putting too much pressure on your water heater. Try to use one of these appliances at a time and restart your unit.

You can also install another tankless water heater, so you don’t need to ration out your water use between machines. 

Reaching Your Minimum Flow Rate

Your minimum flow rate is an amount of water that is measured in gallons, and is what the tankless unit needs flowing through every minute in order to produce hot water.

If you’re not reaching the minimum flow rate, then your heater might turn off as a safety precaution. Increase the flow out of your faucet and see if it makes a difference.

Most tankless water heaters need to be able to detect water flowing through them in order to operate. Some models will operate with flow rates as little as 0.5 gallons per minute, which is usually the lowest minimum flow rate.

Most tankless water heaters provide hot water at a rate of 2.5 gallons per minute. Tankless water heaters that are powered by gas typically produce higher flow rates than ones powered by electricity.

But even the biggest, gas-powered models can’t supply enough hot water for multiple, simultaneous uses across different appliances. 

Something May Be Plugged Up

You might not be getting hot water from your tankless water heater because of a blockage, and it’s important you check the air intake channels and vents. Most tankless water heaters have a notification system that tells you if there is a blocked exhaust vent.

Check that the inside and the outside of your heater isn’t blocked up, and has as little dust as possible. Dirty burners can cause blockages, so ensure that they’re clean.

Check Your Power Source

If your tankless hot water heater is powered by electricity then check the main electrical panel. A problem might have occurred to make the breaker trip. This means resetting the tankless hot water heater before it can work again.

If your tankless hot water is powered by gas then make sure there is propane in your tank, and that the gas valve is turned on.

Temperature Outside

Frozen water pipes in winter can stop hot water from travelling to your appliances. Make sure your pipes have thawed out before trying to use more hot water.

Why Is My Water Running Hot And Then Cold Again?

Why Is My Water Running Hot And Then Cold Again

This is a problem that normally happens when the shower is running, and usually it is caused by somebody using the shower right before you. The water will run hot at first, but then go cold as the hot water heater fills back up with water for your shower.

Once the heater has done its thing, you should have more consistent hot water.

If this becomes a persistent problem, you can always contact your plumber and ask them if they could install a mini tank water heater. This is a small tank that will provide hot water while the main tankless heater warms up. 

This switching between hot and cold is called a cold water sandwich and describes a scenario where the water is warm for a couple of minutes then becomes cold before warming up again quickly.

This happens quite frequently with tankless water heaters, and is particularly common with electric water heaters rather than gas ones. This is because gas heaters reach the optimum temperature almost instantly, while electric heaters will take a while to reach this optimum temperature.

Why Is My Gas Tankless Hot Water Heater Not Igniting?

For your gas tankless water heater to work there has to be proper gas pressure. If your gas tankless heater isn’t igniting, check that the gas valve is open and that all sensors, wiring fuses, and electrical components have not burned out. You should also make sure that there is no condensation or debris on the burners that are preventing ignition. If the flow of pressure isn’t high enough, then the burner will be unable to ignite. This is a frequent problem for gas tankless water heaters no matter what brand and model, but thankfully it is simple to check.

You can check for this problem by finding out what correct gas type (such as natural gas or LP) is used, making sure the pressure is per the specifications, making sure that all air was released from the gas line after installation, and making sure the plumbing was correctly installed per the manufacturer’s instructions.

You should also check if the water pressure is per the specifications and the water is not too hard (7 grains or above), as this can cause sediment to build up. If you live at a high altitude, you should check if the water heater is correctly set, and you should also check for an error code.

Final Thoughts

A tankless hot water heater not only saves money and energy, but they’re quite hardy appliances. However, it is common for them to run into problems from time to time. But these problems can be remedied by being mindful of how many appliances you’re using at one time, and regularly cleaning your tankless hot water heater.

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