“Why am I not getting hot water from my tankless water heater” is the #1 question we get on a daily basis. Here are the answers!
Tankless water heaters are great – energy-efficient, space-saving, and they always provide you with hot water when you ask for it. However, nothing in this world is perfect, nor are tankless water heaters.
For example, they tend to collect more mineral buildup than tank units, provide inconsistent temperature, or take longer to deliver hot water.
7 Reasons Why Am I Not Getting Hot Water From my Tankless Water Heater
So let’s go through some of the most common tankless water heater problems, easy fixes, and other tips on how to maintain this unit’s top-notch performance.
1. Tankless Water Heater Low Flow Problem
Tankless water heater water pressure issues are quite common in fact. If you are simultaneously using multiple hot water taps (washing dishes, taking a shower, and doing laundry), that might overload the unit. However, the catch here is – if you don’t choose a tankless water heater of the correct size (that doesn’t have the needed capacity), you will have flow issues. Even more, the system could stop working completely. 
Unfortunately, there’s no easy fix for this problem. Either you will have to restrain from using multiple taps at the same time or you will have to get replace the unit and get a larger water heater. Alternatively, you can install a second, smaller tankless water heater and keep the old one as well.
If you are experiencing tankless water heater problems occasionally, it could be that you should reset the system, and we’ll explain how to do that in a bit.
2. Tankless Water Heater Shuts Off During Shower
Has this ever happened to you? You are enjoying a warm, relaxing bath, and then, out of nowhere, that lovely stream of water turns stone cold. If your tankless water heater shuts off during the shower, it could be that it is a bit outdated or that you are using an eco-friendly showerhead that is designed to help the environment but also saves water. Your tankless water heater will automatically turn off when the water flow decreases and you’ll have to turn it on the back again manually.
You should either switch to a newer model or change your showerhead to a commercial one that will provide you with a higher water flow. Replacing an old shower head is always a good idea. Limescale, as we mentioned before, tends to cause shower head buildups and drastically reduce the water flow through your tankless water heater, which is why flushing out the system every year is highly recommended. 
3. Tankless Water Heater Providing Hot, Then Cold, Then Hot Water Again
Whenever you take a shower right after someone else has used it, there’s a chance you will end up in the cold water sandwich. The water turns hot, then cold, then hot again at intervals of 6 to 7 seconds, which could be really annoying. This is, at the same time, the biggest downside of tankless water heaters – they can’t provide consistent hot water flow at all conditions.
Plus, if you went for a tankless water heater that is rated low and can’t heat up the amount of water you need per minute, you’ll be regularly experiencing this type of problem.
Whoever takes the shower first will use most of the hot water, while you’ll be actually using hot/warm water leftovers, which is why you will have to come to terms with waiting for some time to pass by until the tankless water heater warms up enough water for you to take a shower.
4. Tankless Water Heater Won’t Ignite
When your tankless water heater won’t ignite, the most common reason for that is – an issue with gas supply. Before taking any further steps, double-check on your propane tank and whether it is full or not. It could also be that either your water or gas valves aren’t fully opened. If your tankless water heater has failed, unfortunately, nothing will help, and you’ll need to hire a professional to sort this out for you.
A gas problem can also result in a flame failure, similar to ignition failure. If you’ve paid your gas bills and your propane tank is full, there could be a problem with venting, regulator, or combustion, and you’re going to need technical support for all of the listed issues as well.
5. No Hot Water to Kitchen Sink
If there’s no hot water coming to your kitchen sink, this could be a flow issue rather than an issue with your tankless water heater. Do you know what is the minimum flow rate of your faucet? To measure how many gallons your kitchen faucet can provide per minute, place a bucket under the faucet, then turn it on.
You should also check what is the minimum flow your water heater requires. To improve the flow within the faucet, remove or drill out restrictions from your faucet and clean it from mineral deposits. Again, it could be other members of your household are using hot water at the same time and the system can’t meet the hot water demand.
6. No Water Coming Out Of My Tankless Water Heater
If no water is coming out of your tankless water heater, it could be two reasons for that – mineral buildup or blocked air supply/exhaust. Hard water contains high levels of magnesium and calcium , minerals that can cause a buildup within the system so that there will be no water coming out of your tankless water heater. Buildups can eventually cause major problems and even impair the function of the unit if you don’t handle the problem on time.
Also, it would be great to clean the water filter every once in a while. For instance, if you are using well water, it will be easier for buildups to form in your tankless water heater. Once this happens, the water won’t be able to reach the heat exchanger or even come out of your tankless water heater.
The second reason is that your exhaust or air supply is blocked and your tankless water heater is displaying an error code. You should check all vent pipes, see whether everything is properly attached, and also double-check the owner’s manual. There, you’ll find info about where to install your tankless water heater. If the unit is installed too close to other objects, this will block the air supply, while rodents and nests can also block your venting. Remove them to re-establish an optimal performance of your tankless water heater.
7. EcoSmart Tankless Water Heater Not Heating Water
If your EcoSmart tankless water heater not heating, it could either be a problem with the thermistors, flow meter, electrical connection, or heating elements, all of which should be inspected by a certified technician.
On the other hand, if your EcoSmart tankless water heater is not heating water, it could be that you went for the wrong-sized unit. EcoSmart’s ability to provide warm water depends on the climate and region you live in. For instance, if you live in a colder climate, you are going to need an EcoSmart tankless with more kilowatts. If you want the best flow rate possible, again, go for a model with more kWs.
How to Reset Tankless Water Heater?
To reset your tankless water heater, turn off all hot water taps/faucets, then firmly press the red reset button located in the center of your tankless water heater’s control panel. Older tankless water heaters typically come with reset buttons located slightly lower. After a few seconds, the button will click. Turn hot water back on and see what happens. Sometimes, you will have to repeat the process 2 to 3 times. If the reset button doesn’t make a click, there could be a problem with some parts of the water heater or the thermostat.
Why am I Not Getting Hot Water From My Tankless Water Heater – Final Word
Whether you are experiencing hot water fluctuation, low flow/low water pressure issues with your tankless water heater, you can, most of the time, troubleshoot the device yourself. Now that you know why you are not getting hot water from your tankless water heater, take the necessary steps to restore its performance. If you find our tips helpful or have any other tankless water heater-related questions, please leave a comment below!