How Often Do Tankless Water Heaters Need Maintenance?

When I was looking for a low-maintenance water heater, someone told me that I should consider a tankless water heater. I was curious, so I began to research tankless water heaters to find out just how much maintenance I could expect them to need.

Tankless water heaters need routine maintenance at least once a year. If you live in an area with harder water, you can expect to need maintenance at least twice a year. The maintenance most required is descaling, a process that removes excess minerals from the system. Other routine maintenance, like filter cleaning, should be done when necessary or at least once a month.

This guide will focus on the different maintenance aspects that one must consider when purchasing a tankless water heater. This will help give you an overview of the different necessary maintenance requirements that they need.

How Tankless Water Heaters Work

Tankless water heaters do not utilize a storage reservoir for the water. Instead,  tankless water heaters directly and instantly heat the water as it passes from your home’s water lines. This means that every time you turn on your hot water, you are triggering your tankless water heater.

Tankless water heaters use heat exchangers to provide the necessary heat to provide warm water. Most heat exchangers are powered by gas or electricity. Understanding how your tankless water heater works is important for understanding why they need proper maintenance.

Why Tankless Water Heaters Need Maintenance

A tankless water heater that is well maintained can last upwards of twenty years. This is one of the most important advantages of properly maintaining your tankless water heater. Tankless water heaters do generally require more routine maintenance when compared to other water heaters.

Tankless water heaters are much more sensitive to water hardness and softness levels, which accounts for the number of minerals present in the water. These minerals can build up much faster inside a tankless water heater and cause blockages and increased energy use.

If you allow these minerals to build up unchecked, it will lower the lifespan of your tankless water heater and cost more money to operate during its lifetime. In some extreme cases, mineral buildup inside a tankless water heater could damage the heat exchanger and effectively render your water heater inoperable.

Even more unfortunate, damage caused by mineral buildup is typically not covered under warranty. This means you will have to pay out of pocket for any repairs or necessary replacement parts. Regular maintenance of a tankless water heater includes descaling, which helps rid the water heater of any mineral buildup.

You should consider getting your tankless water heater descaled at least once a year but other factors can influence the frequency of maintenance.

Factors That Influence Tankless Water Heater Maintenance Frequency

The next section will detail the different factors that could make servicing your water heater more than once a year necessary.  

Hard Water In Your Area

The hardness of the water in your area will directly influence how often you need to perform routine maintenance on your tankless water heater. No matter where you live, the water in your area will contain trace levels of minerals that will build up inside the water heater over time.

The harder the water, the more prevalent these minerals are. If you know that you live in an area with hard water, you should plan to descale your tankless water heater at least twice a year. This will help mitigate the extra minerals and avoid damage to your water heater.

If you are unsure if your water is hard or soft, you can view a map of the mineral levels of water across the US here.

Water Heater Temperature Is Too High

The temperature at which you run your tankless water heater will also influence how often you need routine maintenance. The higher the temperature, the faster the chemicals in the water will break down.

When these chemicals and minerals break down too fast, they can cause limescale buildup, which can damage and clog the internal heating elements. Because of this, you should avoid running a tankless water heater too hot, or else you will have to descale much more often than normal.

Water Heater Temperature Is Too High

You should check your tankless water heater’s thermostat to see what the temperature is set to. If you have been running your tankless water heater above 120 degrees Fahrenheit, then you will likely encounter considerable buildup unless you descale at least once every few months.

There are a few things that you can do to ensure you do not run into issues with your tankless water heater. These are included in the following maintenance checklist.

Tankless Water Heater Maintenance Checklist

Detailed below are some of the most important aspects of tankless water heater maintenance.

Flushing The System

You should flush your water heater at least once a year to ensure no sediment buildup is present in the system. This process is simple and only takes a few minutes to complete. This process is carried out by hooking a hose to the draining valve and draining the water until it is clear.

Tankless water heaters in areas with harder water will need to be flushed much more frequently, as minerals will build up much faster. If you do not flush your system regularly, especially in areas with hard water, it could damage the heat exchanger of your unit.

A damaged heat exchanger will lead to higher operating costs and lower efficiency of your water heater. Most warranties will not cover damage caused by mineral buildup and lack of proper maintenance. Because of this, it is important that you learn how to flush your water heater properly to avoid issues in the future.

To flush your tank properly, first gather vinegar water, a sump pump, and two lengths of hose, then follow the steps below:

1. Shut off the power on your water heater.

2. If you have a gas-powered unit, turn off the gas supply.

3. Turn off the water supply and attach both of the hoses to the pump.

4. Force vinegar water into the water heater using the sump pump.

5. Once you have flushed the water heater with vinegar water, flush it again with water.

This will complete the flushing process. Different makes and models of tankless water heaters will have their approach to flushing and descaling. A descaling kit can be purchased that contains everything that you need to complete this process yourself.

If you are unsure about completing this process on your own, you should consider hiring a professional to take care of it for you. This is the better option unless you are confident that you flush the water heater yourself.

Cleaning The Air Filter

Tankless water heaters utilize a filter to help block any minerals or contaminants in the water as it passes. This filter will require regular cleaning and replacements once they become too dirty or clogged. If the air filter in your water heater is clogged, it will not function properly and can lead to internal damage.

Luckily, air filters are easily cleaned or replaced. If your air filter can be cleaned, simply remove it and use a soft brush with soap and water to remove any obstructions. If it is time to replace it, simply replace it with a new one.  

Cleaning The Water Filter

Most tankless water heaters use an inlet water filter that will also need to be cleaned regularly. How often you need to clean your water heater’s water filter will depend on how often you use it and the quality and hardness of your water.The water filter is designed to trap minerals, contaminants, and other sediments that would otherwise be included in your water. Once these elements begin to accumulate in the water filter, they can reduce water flow and decrease the overall efficiency of your water heater.

Because of this, it is important that you regularly inspect and clean the water filter in your water heater. You should cut off the hot water supply before removing the filter and clean it with warm, soapy water. This will often help clear any blockages and improve water flow if you are having issues.

Cleaning The Tank

Cleaning the outside of your tankless water heater is important to ensure that it functions properly. Any dirt or grime built up on the tankless water heater should be removed using a soft, damp cloth. Dirt and debris on the outside of the tankless water heater could eventually find its way inside and cause issues.

Now that you are aware of some of the key maintenance aspects that tankless water heaters require, you may be wondering when to perform or schedule service.

When To Perform Or Schedule Service

You should perform or schedule service for your tankless water heater at least once a year. This will ensure that any mineral buildup is removed before it can cause other issues inside the water heater. That being said, if you use a lot of water or live in an area with hard water, you will find you need to service your water heater much more frequently.

Maintenance routines, including filter and external cleaning, should be done much more frequently or whenever issues begin to present themselves. A professional can be consulted who will analyze your situation and offer you a maintenance plan based on their expertise.

No Maintenance Tankless Water Heaters?

There is no such thing as a no-maintenance tankless water heater. It is a common misconception that tankless water heaters are low maintenance as they generally require much more than standard water heaters.

A tankless water heater will need to be flushed and descaled much more often than a standard water heater. This is due to the way that they heat the water and their compact design. If you are looking for a more low-maintenance water heater, a standard gas or electric type might be better suited to you.


You can expect your tankless water heater to need routine maintenance at least once every year. This maintenance schedule will help cut down on mineral buildup and prolong the life of your appliance. That being said, usage and water quality in your area will ultimately determine how often your water heater requires maintenance.

If you live in an area with harder water, you can expect to need servicing at least twice a year to keep the mineral levels down. If you are unsure about the water levels in your area or how often you should service your tank, consider consulting a professional.

Leave a Comment