Tankless Water Heater Problems

Tankless water heaters are a great investment for any home. They have a small footprint, are very efficient, and save money by heating water on demand. Issues with a tankless water heater are uncommon. However, problems can arise if something isn’t working properly. Six common water heater problems are mineral build-up, system overload, back-to-back showers, blocked air supply or exhaust, failure to ignite, and flame failure.

Tankless Water Heater Problems

Why am I not getting hot water from my tankless water heater?

Here are the six common issues with a tankless water heater that may be keeping you from getting hot water:

1. Mineral Build-Up

Homeowners must keep a close watch on the mineral build-up inside the water heater. Hard water contains a high mineral content, and the harder it becomes, the more potential there is for the mineral build-up to occur. Magnesium and calcium often cause scaly buildup. It can decrease the correct functioning of the water heater if left unaddressed. If you are upgrading from a traditional tank, check the water filter in the heater- especially if you are dealing with well-water. Traditional water heaters don’t require frequent cleaning. However, tankless systems need more maintenance for longer durability. Well water causes a rapid accumulation of debris, making it difficult for water to go through the path to the heat exchanger. Debris can get trapped if the water filter doesn’t stop it. Flush the water heater every six months. You can also use a water softener to slow the accumulation of debris.

2. System Overload

Depending on the capacity, too many applications going on at the same time can overload the water heater. It may struggle to provide hot water or completely shut down. If this occurs, reduce the demand for hot water by not running so many things at once. If the water heater becomes overloaded frequently, you may need to upgrade it to a higher capacity or add another unit. While it may appear to be a large investment, it may save money since you’ll use less water while waiting for hot water to arrive.

3. Back-to-Back (to Back) Showers

Sometimes when everyone showers one after another, the hot water simply runs out. The next person gets a shower that begins warm, becomes cold, then returns to warm when the water reheats. With a tankless water heater, after the first shower, hot water remains in the pipes. When the second one begins, the first warm water is trapped. Tankless heaters are instantaneous heaters because they only heat water when needed. If you experience cold water, it is because cold water is residing in the pipes located between the water heater and the shower. The further it needs to travel to its destination, the larger the gap. Homeowners can’t prevent it, so you may want to be mindful to wait just a bit before jumping in the shower.

4. Blocked Air Supply or Exhaust

Most tankless water heaters will give an error code to notify you of any blockages. When it does, it means that the heater is having issues with venting or combustion air. Inspect the vent pipes to make sure they are properly connected and don’t have holes. Read your product manual to ensure your water heater meets all clearance requirements. If the water heater is close to other objects or there isn’t enough room due to clutter, it can block the air supply. It is also a fire hazard. Wasp nests, beehives, bird’s nests, and rodents can block venting. Make sure to examine all vents located in and leading outside the home.

5. Failure to Ignite

Failure to ignite may be a gas supply issue, so check to see if the propane tank is full before doing anything else. If the gas or water valves aren’t completely opened, this could also cause the ignition to fail, resulting in cold water. If the issue still isn’t resolved, the ignition pack may have failed or there is a bigger issue. You may want to consult an expert.

6. Flame Failure

Flame failure happens from either gas pressure or electrical issues. First, eliminate simple causes like a low propane tank or an unpaid gas bill. Other causes can be too small gas lines, regulator failure, venting, combustion issues, and more. Contact a professional for help.

How Do You Troubleshoot a Tankless Water Heater?

If there is no hot water, check the electricity, gas, and water supplies to the water heater. Ensure the shut-off valve hasn’t been closed. Then, check the gas burner. Does the flame rod spark when the unit turns on? If the answer is no, then it is an ignition failure problem.

Check the control panel for error codes to find out what may be preventing the heater from providing hot water.

Ensure you have the minimum water flow, the tap is fully opened to meet the required flow, and nothing is blocking the piping line.

Are elements or pipes frozen? Ensure that all pipes exposed to the outdoors are insulated and the heater is covered with an insulation jacket to prevent freezing and damage.

If the water is too hot, the temperature may be set too high. Reduce it to prevent scalding, high operating costs, and energy waste. Reduced water flow caused by obstructions may cause only a small portion of water to heat, giving you higher temperatures. Therefore, clean the passageways.

Make sure there is no sediment build-up. If there is, do flushing and descaling. The temperature sensor may also be broken or incorrectly positioned. Try to reposition or replace it.

If there is no ignition and there is no flame, check to see if the gas, water, and electricity are on. Make sure the gas pressure and type are correct and that the gas line is properly sized. Bleed air from the gas line, then check if the wiring harness and flame rod are working (not loose, damaged, or in the wrong spot).

Also, check if there is excessive condensation or moisture, which could extinguish the flame.

If the heater is too noisy, check the fan to see if anything is blocking it. Inspect the burner to see if the gas is burning with a clear, light blue flame. Make sure there are no leaks in the sealed combustion and that your burner flames are not unstable.

Instant tankless electric water heater installed on white tile wall

What Is the Downside of a Tankless Water Heater?

There are a few cons to a tankless water heater, and they are as follows:

  • High-cost installation cost and cost of water heater
  • It takes longer to receive hot water
  • “Coldwater sandwich” a.k.a back-to-back-to-back showers
  • When multiple appliances are running, there may be inconsistent water temperature
  • Lukewarm temperature is difficult to achieve
  • No hot water during power outages

Tankless water heaters are a great investment because they cut costs on energy bills by only heating water on demand. They have a smaller footprint and have more flexibility in terms of where you can install them.

However, as with anything, there are a few cons to consider as well. While it may take a while for the water to heat up, you can say the same for traditional heaters. However, with traditional heaters, the wait time appears to be longer. Traditional heaters can equally be noisy and have problems of their own.

Examine our options when selecting a water heater to determine which is the best fit for your house, the size of your family, and your hot water needs.

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