Do Tankless Water Heaters Need Maintenance?

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Investing in a tankless water heater is an excellent way to reduce related energy costs and enjoy the benefit of a steady supply of hot water on demand. However, as amazing as a tankless hot water heater can be for you and your family, you don’t want to overlook the importance of preventive maintenance.

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All mechanical devices and equipment must be maintained regularly for optimal longevity and efficiency, and a tankless water heater is no different. Understanding why it’s important and what needs to be done can help you plan for this process.

Common Issues With Tankless Water Heaters

Maintaining your tankless hot water heater can help you avoid downtime related to repair issues. It can also potentially help maximize the longevity of your unit and promote energy efficiency over the months and years. Water hardness is one of the more significant factors that can result repairs, but regular system maintenance steps can diminish the effects of hard water.

Hard water is full of minerals, and these minerals can result in scaling and other issues inside your system. While water hardness is dependent on region, even homeowners in areas known for low levels of may face these same repair and maintenance issues. After all, all tap water that flows through your system has at least trace elements of minerals that can build up over time.

See Also:  Condensing vs Non-Condensing Tankless Water Heaters

How Tankless Water Heater Maintenance Helps

You can schedule service or take a do it yourself approach to deal with maintenance. The primary type of maintenance service that’s needed for most of these units relates to cleaning the system in different ways. If minerals have caked onto the components in the unit, descaling efforts must be made. To greatly reduce buildup, installing an inline filter is a good investment.

Otherwise, a general cleaning is beneficial. These steps help your system to operate with peak efficiency and reduce related energy costs. In addition, these steps may reduce unnecessary wear and tear, and they may potentially help your unit to last longer.

Descaling Process

how to flush tankless water heater 2

If you live in an area with hard water, descaling is necessary from time to time. Descaling is the process that involves removing the accumulated gunk inside of your system. The minerals in the water can settle in your system to create a thick mess.

The descaling process is similar to the flushing and cleaning process below. However, it also involves running a significant amount of water vinegar through the tank. Vinegar will break down the mineralized gunk inside your unit.

Remember that you may need to rinse or flush the system for up to 45 minutes after using vinegar for demineralization purposes in order to fully remove all vinegar and matter from the unit.

Here are descaling instructions for the most common tankless water heater manufacturers:

Here’s a good video showing the process:

Flushing the System

Regardless of the level of water hardness in your area, all tanks should receive regular cleaning. The process is a bit more involved than flushing a storage tank water heater but pretty straightforward. The frequency of this service may range from between 6 to 12 months in many cases. The flushing process requires you to follow the manufacturer’s instructions.

Related: How to Flush a Tankless Water Heater (Step-by-Step)

Generally, you will shut off the power and water supply to the water heater, attach a short hose to each of the isolation valves, connect a small pump to the end of the cold water hose, and then place both the end of the hot water hose and circulation pump inlet hose into a 5-gallon bucket of water.

You’d turn on the pump and have it circulate water through the tankless water heater for about an hour. The force of the water through the system will help to clean the system and may remove any minerals that have been deposited in the unit.

When to Perform or Schedule Service

Now that you understand the importance of maintaining your tankless water heater and the steps required, you must decide how frequently to complete the cleaning. More than that, you must decide if you’ll do it yourself or if you’ll use a professional.

While these rudimentary steps may sound simple enough to complete, you need to understand which valves control which aspects of the unit before you start fiddling with it. In addition, you want to ensure that your efforts sufficiently clean the system.

If you’re planning to schedule service with a plumbing company, consider doing so today. Your plumber can then inform you of a recommended frequency for maintenance services on your tankless water heater in the future.

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Get a free estimate online from top local home service pros in your area.

If your tankless water heater goes out of commission, you may have to live with the inconvenience of having not hot water until the unit is repaired. In addition, the cost to repair is almost always higher than preventive maintenance. While you can’t prevent all types of issues from happening, you’ll be at a much lower risk of one occurring. By reading through your product manual, you can learn more about the specific maintenance steps required for your particular model.

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  1. The quantity of vinegar required has to do with basic chemistry. The vinegar is a mild (acetic) acid. The scale that you are trying to remove is a base (lime or calcium carbonate.) The acid dissolves the base until the solution is neutral ph. If you don’t use enough acid, the solution will be neutral ph before the base is all dissolved. Running the system longer after the solution is no longer acidic accomplishes nothing. If the manufacturer recommends a certain amount of vinegar, use it!

    • Roger,

      This is an excellent comment and something I had never run across in my research, and is almost never mentioned by the ‘experts.’ Having a chemistry minor, I really should’ve figured it out myself. Thanks for this insight!

  2. It’s interesting how you talked about how maintaining your tankless water heater is better than having to repair it. I’ve been in the house I live in for 3 years and I’ve started to become worried about the tankless water heater since I don’t know how to maintain it myself and I don’t want it to break, so I’m glad that you talked about why maintenance helps. I’ll make sure to look into hiring someone to check it out soon, thank you!

  3. Professionally flush ever year, and am told I now need to ” pull and service ” some sort of heads. The Price $800 + tax. It is a 10 year old Rinnai. Do you know what this might be, or what it is, and is the price reasonable? I feel the plumber is reliable. How often does it need to be done, and how long should my tankless last? I really like it.

    • Just read this question … not sure what “heads” means? But if this is a Rinnai non-condensing (RL75 or 94i)
      Every 5-7 years should pull burner and blow out w/130 psi air, also clean electrodes at same time. This can be done simultaneously while descaling unit. Shouldn’t take longer than 1.5 – 2 hrs $500-600 in Chicago suburbs.

      • Also… if unit has never been descaled b4 … may want to think twice about doing service. Could open up a pre-existing leak because of limescale build-up. Rec to wait till LC or 00 code comes up … start budgeting for new unit. Max time between flushing 3 years at 10 grains hardness and 120 degree set temp and couple adults in household.

  4. I have a Rinnai and can’t figure out how to open the in-line filter. I’ve seen videos but never a close up showing how to open it and I don’t want to break it.


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