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Writer's pictureCorbin Moyer

Stop Wasting Money! The One Maintenance Tip Every Tankless Water Heater Owner Needs



Tankless Water Heater

Let’s talk about something that doesn’t get enough attention but could save you a lot of hassle, money, and cold showers: flushing your tankless water heater. This sleek, efficient piece of equipment is the workhorse behind your endless hot water supply, but it needs some love to keep doing its job right. Trust me, as a plumber who’s seen it all, you don’t want to wait until your water heater throws in the towel.


What’s the Big Deal About Flushing a Tankless Water Heater?


Your tankless water heater is like the superstar of your home. It heats water on demand, saves space, and cuts energy costs. But if you ignore it, it’ll start acting up in ways you won’t like. Flushing it regularly keeps it happy, efficient, and working like a champ.


The Gross Truth About Mineral Buildup


Here’s the thing: water isn’t always as pure as we’d like to believe. If you’ve got hard water (and statistically, 85% of homes in the U.S. do, according to the U.S. Geological Survey), minerals like calcium and magnesium are hitching a ride into your tankless water heater. Over time, these minerals form scale and clog up the heat exchanger, which is basically the heart of your system.


Scale buildup isn’t just gross; it’s a troublemaker. It makes your heater work harder, wear out faster, and could even cause it to stop working entirely.


What Happens When You Don’t Flush Your Tankless Water Heater?


1. It’ll Cost You More Money


A tankless water heater struggling under a layer of mineral deposits is about as efficient as trying to run a marathon in flip-flops. According to the Department of Energy, heating water accounts for about 18% of a home’s energy use. A poorly maintained tankless system can increase that number by 25-30%. Imagine watching your energy bill climb because your heater can’t do its job efficiently.


2. Shorter Water Heater Lifespan


Tankless water heaters are built to last 15-20 years with proper care. But if you let scale pile up, don’t be surprised if your heater taps out early. Regular flushing can add years to its life. Think of it as your tankless heater’s secret to longevity.


3. Noisy Neighbors in Your Utility Closet


You know that weird whining or whooshing noise? That’s not a ghost; it’s your tankless water heater crying out for help. Scale restricts water flow and creates pressure issues, causing these annoying sounds. It’s like your water heater’s way of saying, “Help me out here!”


4. Lukewarm Showers and Long Waits for Hot Water


When mineral buildup clogs the heat exchanger, your water heater struggles to keep up with demand. The result? Tepid showers and the frustrating experience of waiting an eternity for hot water.


How Hard Water Accelerates Efficiency Loss


Did you know that the type of water flowing through your pipes plays a massive role in your tankless water heater's efficiency? Hard water, which contains higher levels of dissolved minerals like calcium and magnesium, accelerates the scaling process in your tankless water heater. These mineral deposits coat the heat exchanger, reducing its ability to transfer heat effectively. Over time, this leads to a significant drop in efficiency and can even cause permanent damage.


Efficiency Loss vs. Mineral Buildup Levels


To illustrate how mineral buildup affects efficiency, here’s a graph showing how scale thickness (measured in millimeters) impacts efficiency:



Tankless Water Heater

The Hard Water Connection


Research shows that just 1 millimeter of scale buildup can reduce your system’s energy efficiency by up to 10%. Hard water users may see this level of buildup in as little as 6 months without regular maintenance. In areas with extremely hard water (≥ 15 gpg), scaling can reach 6 millimeters or more in under 2 years if left untreated.


How Flushing Prevents the Damage


Flushing your tankless water heater removes this mineral buildup before it can cause costly damage. For homes with:

  • Normal Water: An annual flush is usually sufficient.

  • Hard Water: Flushing every 6 months is strongly recommended.


Pairing this maintenance with a water softener can drastically reduce scaling and prolong your system’s life.


So, What Does Flushing a Tankless Water Heater Involve?


Without getting into the nitty-gritty, here’s the gist:

  • A descaling solution is circulated through the system to dissolve and remove mineral buildup.

  • The process requires shutting off the water and power supply, attaching a pump, and running the solution for a set amount of time.

  • It’s not rocket science, but it’s best left to someone who knows what they’re doing to avoid damaging delicate components.


How Often Should You Flush Your Tankless Water Heater?


Once a year is the gold standard, though homes with especially hard water might need it more often. It’s not a ‘set-it-and-forget-it’ appliance. Regular maintenance is key to keeping it running smoothly. Think of it like going to the dentist—annoying but necessary.


Why You Should Call a Professional


Sure, there are DIY guides out there, but do you really want to risk voiding your warranty or messing up an expensive system? A pro will:

  • Use the right tools and techniques.

  • Inspect for other issues while they’re at it.

  • Ensure your heater is working as efficiently as possible.


Plus, you get to relax and not worry about accidentally turning your utility closet into a water park.


Final Thoughts


Flushing your tankless water heater isn’t just about keeping the hot water flowing; it’s about protecting your investment, saving energy, and avoiding the misery of lukewarm showers. Make flushing part of your annual maintenance routine, and your tankless water heater will reward you with years of reliable performance.


Don’t let scale win. Your water heater deserves better, and so do you. Call a professional (hint: someone like me!) and let’s give your tankless water heater the care it needs to keep your hot water flowing.




  1. U.S. Geological Survey (USGS): "Hard Water and its Impact on Water Systems," available at usgs.gov.

  2. Water Quality Association (WQA): "Understanding Hard Water and Scaling in Appliances," available at wqa.org.

  3. American Water Works Association (AWWA): "Regional Variations in Water Hardness Across the U.S.," available at awwa.org.

  4. Department of Energy (DOE): "Energy Consumption and Maintenance for Water Heaters," available at energy.gov.

  5. Energy Star: "Tankless Water Heater Maintenance Tips," available at energystar.gov.

  6. Rheem Water Heating Systems: "Proper Care and Maintenance of Tankless Water Heaters," available at rheem.com.

  7. International Journal of Heat and Mass Transfer: "Effects of Scaling on Heat Exchanger Efficiency," available at sciencedirect.com.

  8. American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE): "Scaling and Its Effect on Water Heating Systems," available at ashrae.org.

  9. Navien, Noritz, and Rinnai Manufacturer Manuals: "Maintenance Guidelines for Tankless Water Heaters," available on their respective official websites.

  10. Plumbing and HVAC Industry Publications: "How Scaling Reduces Efficiency in Tankless Water Heaters," available at phcppros.com.

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