How to Flush Your AO Smith Tankless Water Heater Like a Pro

Tankless water heaters are the space-saving superheroes of home hot water. But even these mighty minis need a little TLC now and then. Especially in areas with hard water, mineral buildup can creep in and reduce their efficiency. The good news? Flushing your AO Smith tankless water heater is a relatively simple process that can extend its lifespan and keep your hot water flowing freely.

Flush Your AO Smith Tankless Water Heater

Why Flush Your AO Smith Tankless Water Heater? It’s All About Performance

Think of your tankless water heater like a hardworking athlete. Mineral buildup, also known as scaling, acts like tiny weights, hindering its performance. Here’s how:

  • Reduced Heat Transfer: Scale acts like an insulator, making it harder for the heater to transfer heat efficiently to the water.
  • Decreased Water Flow: Buildup can narrow water passages, leading to a weaker flow at your faucets.
  • Lifespan Matters: Regular flushing helps prevent malfunctions and keeps your tankless water heater running strong for years to come.
  • Warranty Considerations: Some AO Smith warranties might require proof of periodic flushing, so be sure to check yours!

Preparing for the Flush: Gear Up for a Smooth Process

Before we unleash the descaling solution, let’s gather the essentials for a successful flush:

Flushing Essentials:

Descaling Solution: Choose a product specifically formulated for tankless water heaters. Always follow the manufacturer’s instructions for dilution!
Circulation Pump: A small pump helps efficiently circulate the descaling solution through the system.
Buckets: To hold the descaling solution and collect wastewater.
Hoses: The right size and length to connect the pump to your water heater’s designated flushing points.
Safety Gear: Eye protection (goggles) and gloves are recommended, depending on the descaling solution.

AO Smith Tankless Water Heater Flushing Kits: Convenience vs. Cost

AO Smith offers flushing kits that include a compatible descaling solution and all the necessary connectors. While convenient, these kits might be pricier than gathering the supplies yourself.

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Step-by-Step Guide: Flushing Your Way to Hot Water Harmony

Now for the fun part – the actual flush! Remember, this is a general guide. Always prioritize the instructions in your specific AO Smith tankless water heater’s manual.

  1. Safety First: Turn off the water heater and allow it to cool completely.
  2. Isolating the Unit: Locate and close the hot and cold water shut-off valves connected to your water heater.
  3. Connecting the Pump and Hoses: Refer to your manual or kit instructions for the designated attachment points on your AO Smith model.
  4. Descaling Solution Prep: Dilute the solution according to the product’s recommendations.
  5. Circulation Time: Run the pump for the duration specified in the descaling solution instructions and your AO Smith manual.
  6. Neutralizing Flush (Optional): Some solutions might require a follow-up flush with clean water to neutralize any remaining acidity.
  7. Restoring Connections: Reopen the hot and cold water shut-off valves, and turn on the power to your water heater.

When to Flush Your AO Smith Tankless Water Heater: Keeping It Clean

  • Hard Water Havoc: If you live in an area with hard water, more frequent flushing (every 6 months) might be beneficial.
  • Performance Decline: Notice a decrease in hot water flow or heating capacity? Flushing might be the solution.
  • Recommended Schedule: Check your AO Smith owner’s manual – they may recommend a specific flushing frequency.
  • Preventative Maintenance: Regular flushing is a proactive approach to maintaining your tankless water heater’s efficiency and lifespan.

By following these steps and consulting your AO Smith manual, you can successfully flush your tankless water heater and keep it operating at peak performance. Still feeling a little unsure? No worries! Check out the resources below for additional support.

  • AO Smith Website: offers troubleshooting guides and FAQs.
  • Tankless Water Heater Flushing Guide: (This video provides a general overview of flushing tankless water heaters, not specific to AO Smith models).
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So there you have it! With a little preparation and this guide, you’ve got the knowledge to conquer hard water buildup and keep your AO Smith tankless water heater delivering hot showers for years to come.


I am a mechanical engineer and love doing research on different home and outdoor heating options. When I am not working, I love spending time with my family and friends. I also enjoy blogging about my findings and helping others to find the best heating options for their needs.