A tankless water heater attached to a bathroom wall.

Annual Tankless Water Heater Maintenance Requirements

A tankless water heater (sometimes also called a demand-type water heater or an instant water heater) is a type of water heater that only provides hot water as it is needed. For this reason, they tend to be more energy-efficient than water heaters with storage tanks, and as a consequence, they also tend to be better for your finances. Since tankless water units do not have a storage tank, when you turn the system on by turning your faucet or showerhead to hot, you are essentially turning on the water heater itself.

Below we will go into more detail on just how tankless water heaters are able to do this and what process they go through. Before we go on to talk about tankless water heaters and their advantages, here is a quick rundown of all the other main types of water heaters that homeowners use to heat up the water in their homes.

The Conventional Storage Water Heater:

  • It is the most commonly found type of water heater
  • It is usually the most affordable type of water heater
  • It is the easiest-to-install type of water heater
  • It should last you around 25 years
  • It requires twice-yearly maintenance in order to last longer
  • It can only provide as much hot water at once as the tank holds
  • It can take a while for the tank to fill back up with hot water once it is empty

The Heat Pump Water Heater or Hybrid Water Heater:

  • It is even more energy-efficient than tankless models
  • It can save you money in the long run
  • It should last you around 13 to 15 years
  • It will not work well in cold climates or if it is installed in cold rooms
  • It can be a costly initial purchase
  • It requires a considerable amount of space due to its pump
A solar water heater on a roof.

Solar water heaters can be quite cost-effective in sunny and warm locations.

Solar Powered Water Heater:

  • It is the most energy-efficient type of water heater
  • It is the most eco-friendly type of water heater
  • It should last you around 25 years
  • It can be an expensive system with the additional cost of solar panels
  • It will not work well in climates without a considerable amount of sun

Condensing Water Heater:

  • It is a very energy-efficient type of water heater
  • Its large storage tank will make sure there is enough water for your whole home
  • It should last you around 15 years
  • It is only recommended for households that use natural gas as their primary energy source
  • It is only recommended for larger households as smaller versions can be hard to find

You can read more about the different types of hot water heaters here.

How Do Tankless Water Heaters Work?

As the name suggests, tankless water heaters work without the need for a storage tank. This means that the water will be heated between your main water line and your faucet. When you turn on your hot water tap, the cold water will go through your main water line into the heater system. At this point, either a gas burner or an electric element will heat up your water and send it back through your pipes into your faucet. Because this process happens on-demand, you are able to have an endless supply of hot water, as opposed to what happens with heaters with storage tanks, where you have to wait for the storage tanks to fill up with hot water.

The only downside to a tankless water heater system, when compared to one with a storage tank, is that the water flow rate is often slower. As a general rule, a tankless water heater will provide hot water at a rate of 2 to 5 gallons, or 7.6 to 15.2 liters, of water per minute (often shortened as GPM). This means that if you try to run these water heaters on too many fixtures (so if you try to take a shower, run the dishwasher and the washing machine all at the same time) you might be pushing these products to their limits.

The solution to this problem, however, is simple – you can install two or more tankless water heaters (depending on the size of your home, you might need either less or more). You can connect them in parallel for simultaneous demand so you can provide hot water for your whole home easier, or you can install them separately for different appliances, in the case that you have appliances that use an exceptional amount of hot water, such as a laundry machine or a dishwasher.

A gas tankless water heater often has a higher water flow rate than an electric tankless water heater, so in case you have a higher need for hot water or a larger home than most, you might want to look into a gas model rather than an electric one. You should, however, be aware that gas tankless units are often more expensive than electric ones, and less environmentally friendly.

Tankless Water Heater

What Are The Advantages Of A Tankless Water Heater?

There are several advantages to purchasing a tankless water heater. Here are the most significant ones.

Tankless Water Heaters Are Energy Saving

A tankless water heater is more energy-efficient than its counterparts with storage tanks. If your home uses 41 gallons of hot water or less every day, then a tankless water heater can be 24 percent to 34 percent more energy-efficient than storage tank water heaters. If you and your family use around 86 gallons of hot water per day, then a tankless water heater will be 8 percent to 14 percent more energy-efficient. If you choose to install more of these types of water heaters in your home, such as possibly one at every hot water outlet, then you can expect quite significant energy savings of 27 percent to 50 percent.

Tankless Water Heaters Last Longer

The average lifespan of a tankless water heater is around 20 years. You can raise your children from conception until legal adulthood and this type of water heater will likely still be providing you with endless hot water. Although some other types of water heaters, such as the conventional storage tank type, are said to last longer (around five years more), the added benefit of 20 years worth of saving on your electricity bill is likely going to trump losing a few years on its lifespan.

Tankless Water Heaters Are Space-Saving

Due to the fact that these types of water heaters do not have a need for a storage tank, they are consistently more space-saving than any other types of water heaters. Even if you are forced to install more than one in your home because of your household’s higher demand for hot water, you are still likely to be saving space by getting this type of water heater.

Tankless Water Heater Provide You With Endless Hot Water

One of the tankless unit’s most appealing advantages is that it can provide you with an endless stream of hot water. Unlike its storage tank bearing counterparts, this kind of water heater does not need to wait for a whole tank to fill up with hot water and can provide it on-demand at all times, and for as long as it is needed. Although, as mentioned above, this sometimes can influence the water flow rate, the ability to have as much hot water as needed can be extremely appealing as often trump all other concerns.

You can read more about the advantages of tankless water heaters and how they work here.

How Do I Choose The Right Tankless Water Heater?

There are several things you need to keep in mind in order to get not only the right type but the best type of tankless water heater for your home.

  • Type of heating process – you might prefer a gas burner since it will give you a higher flow rate, or a heating element, which is less expensive and more environmentally friendly
  • The size of the tankless water heater – meaning how many fixtures can it cover and how many can it cover at the same time
  • Anti-scale devices – if your tankless water heater comes with an anti-scale device (a sort of water softener device), it will require a great deal less maintenance
  • The amount of energy it will save you – different models will have different energy-saving capabilities
  • The cost of the product – you should make sure you are getting a good price-to-quality ratio
  • The warranty – different tankless water heaters will come with different types of warranties
A water heater being repaired with a wrench.

Professional installation and routine maintenance of tankless water heaters can increase their lifespan.

How Long Does A Tankless Water Heater Last?

The average lifespan of a tankless water heater is around 20 years, which is a longer lifespan than that of a heat pump water heater and a condensing water heater. A regular storage tank water heater is likely to last around five years longer, but will definitely cost much more in electricity bills in the long run.

A solar-powered water heater is also said to last around 25 years, but they are often inaccessible to people who do not have the means for an original investment in solar panels and the water heater itself. This means the tankless water heater model remains one of the longest-lasting, most energy-saving models you can get.

It is important to note that this type of water heater (as with all other types) will not last you as long without the proper maintenance. Although tankless water heater systems require less maintenance than all other types, it is still important to be aware of what you can do to get it to last 20 years, or even 30 years if you take care of it perfectly.

How Much Maintenance Does A Tankless Water Heater Require?

Before we start talking about maintenance, we need to talk about the very first thing you will do with a tankless water heater – installation. Installation is key with these products, and can easily determine how much maintenance you will have to do as well as how long the lifespan of your product will be. Here are some of the factors that can determine whether the product was installed properly:

  • The type of tankless water heater
  • The climate you live in
  • Your local building code requirements
  • Safety issues

This is why it is often recommended that you get a plumber to install this type of product for you. Since the installation process can be extremely complicated, sometimes dangerous, can affect how long your water heater will last, and can sometimes even dictate how long your warranty will last, it really might be the best idea to get a professional to do it for you. If you decide to get one to help you with installation, there are some things that you should do to make the process better for you:

  • You should request cost estimates in writing
  • You should ask for references if you can
  • You should check the company with your local Better Business Bureau
  • You should also see if the company will obtain a local permit if necessary and understands your local building codes

If you do decide to try and install the tankless unit by yourself, you can consult the manufacturer, since they will have instruction manuals and will be able to tell you about proper installation. You can also contact your city or your town for information on getting a permit if you need one, as well as learn about your local water heater installation codes.

Now onto maintenance. You should make sure you do some routine maintenance on your tankless water heater at least once a year since hard water can create buildup and lower its lifespan. Product-specific maintenance will be specified in the instruction manual that will come when you purchase the product.

An electric heating element covered in limescale.

Limescale is a hard chalky deposit usually found on surfaces where “hard water” has evaporated.

Hard water is defined as a type of water that is heavy in minerals such as calcium and magnesium. These types of minerals will build up around your pipes and inside your water heater, and will prevent the natural flow of the water, lowering your water flow rate and making your tankless water heater work harder than it would otherwise. Mineral deposits will mean that your water heater will likely break sooner, and will likely need replacement sooner as well.

Minerals such as calcium and magnesium are found in water supplies everywhere, but there are certain places where you are more likely to have hard water than in others. If you live in a place with especially hard water, you might want to do routine maintenance on your water heater twice a year instead of once.

The most important thing to do maintenance wise is clean out the limescale buildup (as well as any sediment) on the heat exchanger, which is caused by hard water. This is the part of your tankless water heater most susceptible to mineral buildup issues, which you can take care of by cleaning it out once a year. Most manufacturers will not cover buildup damage on the heat exchanger in their warranties.

Unless you have some plumbing experience, you should probably get a professional to do it for you. In a routine maintenance visit, a professional will both de-lime and descale your water heater so that any mineral buildup will be gone.

If you decide to do maintenance on your tankless water heater yourself, then you should first read the maintenance section of your instructions manual and make sure that you follow it to the letter to avoid creating more issues that might lower your water heater’s lifespan.

Here is a breakdown of how descaling your tankless water heater works:

  • Disconnect the electrical power that feeds the heater
  • Remove the access panel
  • Locate and close the gas isolation valve
  • Locate the hot and cold shut-off valves and close them too
  • Locate the hot water pressure relief valve and open it
  • Connect hoses to both the cold water and the hot water ports
  • Place the submersible pump into a five-gallon bucket
  • Connect the cold water hose to the pump
  • Place the free end of the hot water hose into the bucket
  • Pour four gallons of white vinegar into the bucket
  • Open the hot and cold service ports and turn the pump on.
  • Allow the vinegar to go through the heater for one hour
  • Turn the pump off and dump the vinegar
  • Close the cold water service port and remove the hose
  • Open the cold water shut-off valve to flush out any remaining vinegar, then close it
  • Let the water drain and remove the second hose
  • Close the hot water service port
  • Remove the cold water inlet filter and (if present) hot water in-line filter
  • Flush the filters at the sink to remove leftover sediment

How Do I Know My Tankless Water Heater Needs Replacing?

There are several ways to know that your tankless unit might be at the end of its service life, and it is important to be able to recognize them when the time comes.

Your Tankless Water Heater Is Making Strange Noises

It is not uncommon for water heaters to make noise while they are working; however, if you start to hear strange sounds coming from your tankless unit, you might want to open it up and check for mineral buildup or corrosion.

Your Tankless Water Heater Gives You Tinted Water

If you see red or yellow water coming from your faucet every time you turn the hot water tap on and you see only clean water when you turn the cold faucet on, you might be dealing with a deadly case of rust in your water heater.

Your Tankless Water Heater Gives You Lower Temperature Water

This is a more intuitive one, but if your tankless unit is no longer producing hot water, and it is toward the end of its average lifespan, it might have just hit its breaking point.

Your Tankless Water Heater Has Water Pooling At The Base Of The System

If you notice leaks or water pooling around this system, it could very well be due to cracks or corrosion in the system. This is usually a death sentence for not only tankless water heaters but all other types of water heaters too.

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Joshua Perkins

Joshua spent ten years as a water systems technician in California before settling down with his wife and two young children in Nashville in 2018. Through all of his experience, he learned the benefits and shortfalls of so many different types of water filtration systems, from pitchers to whole-house installations. He started Water Filter Authority in 2019 to empower other families to make the right decision for their long-term health and wellness.