Tankless Water Heater Maintenance: How to Keep Yours Running Like New

Tankless water heaters are famous for their long life and efficiency—but only if you keep them in top shape. A little regular maintenance goes a long way, preventing hard water scale, costly repairs, and annoying error codes. Whether you’re a DIYer or just want to know what to expect from your plumber, this complete guide will show you how to maintain any tankless water heater (gas or electric), extend its lifespan, and enjoy endless hot water year after year.

Quick Picks: Best Tankless Water Heater Maintenance Kits & Tools

Why Tankless Water Heater Maintenance Matters

  • Prevents Hard Water Scale: Minerals can build up inside the heat exchanger, reducing efficiency and leading to early failure.
  • Avoids Error Codes: Clogged heaters may throw codes like “LC” (lime scale) or “E1” (flow issues), shutting down your system until cleaned.
  • Protects Your Warranty: Most brands require annual maintenance to keep the warranty valid.
  • Extends Heater Life: A well-maintained tankless heater can last 15–20 years or more.
  • Saves Energy: Scale buildup forces your heater to work harder, costing you more on energy bills.

Step-by-Step: How to Maintain a Tankless Water Heater

  1. Turn Off Power and Gas: For safety, shut off electricity at the breaker and close the gas valve (for gas units).
  2. Shut Off Water Supply: Turn off the cold water inlet and hot water outlet valves.
  3. Attach Service Hoses: Connect a hose to the hot and cold service ports (usually blue and red), leading to a bucket.
  4. Add Descaling Solution: Pour your flush solution (like Calci-Free) into the bucket.
  5. Run the Pump: Place a small sump pump in the bucket and circulate the solution through the heater for 45–60 minutes.
  6. Flush with Clean Water: After descaling, flush the system with fresh water for 5–10 minutes to remove any leftover cleaner.
  7. Reassemble and Restore Power: Close service ports, open main valves, turn on gas and power, and check for leaks or error codes.
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Tip: Flush your tankless water heater once a year (twice in hard water areas) for best performance and longest life.

Buyer’s Guide: What You Need for Tankless Water Heater Maintenance

  • Flush Kit: Includes hoses, pump, and bucket—everything you need to circulate descaler.
  • Descaling Solution: Use a non-toxic, tankless-safe cleaner for best results.
  • Service Valves: Make sure your unit has isolation valves installed. If not, have a plumber add them—they make maintenance easy and fast.
  • Water Filter: An inline scale filter helps prevent future buildup, especially in hard water areas.
  • Wrench & Screwdriver: Basic tools for opening panels and attaching hoses.
  • Owner’s Manual: Each brand may have specific instructions—always check before starting.

Top Products: Maintenance Kits & Scale Prevention

My PlumbingStuff Tankless Water Heater Flushing Kit

  • Includes 1/6 HP pump, hoses, bucket, and step-by-step guide
  • Compatible with all major brands: Rinnai, Noritz, Rheem, Navien, Bosch, and more
  • Durable and reusable year after year

Final Verdict: Best all-in-one flush kit for homeowners or pros.
See it on Amazon

RectorSeal Calci-Free Tankless Water Heater Flush

  • Non-toxic, biodegradable, and safe for all heaters
  • Removes calcium, lime, and rust deposits fast
  • Trusted by plumbers nationwide

Final Verdict: The easiest and safest way to descale your system.
Check price on Amazon

APEC 1″ Polyphosphate Inline Scale Filter

  • Prevents scale from ever forming in the heat exchanger
  • Easy to install, lasts 6–12 months per cartridge
  • Protects your heater, fixtures, and appliances

Final Verdict: Must-have for hard water areas—reduces future maintenance.
See details on Amazon

Comparison Table: Best Tankless Water Heater Maintenance Products

Product Main Use Includes Pump? Reusable? For Hard Water? Price Link
My PlumbingStuff Flush Kit Annual flushing Yes Yes Yes View
RectorSeal Calci-Free Descaling solution No N/A Yes View
APEC Scale Filter Scale prevention No Yes Yes View
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FAQ: Tankless Water Heater Maintenance

  • How often should I flush my tankless water heater?
    Once a year is standard—twice yearly in hard water regions or if your heater is used heavily.
  • What happens if I skip maintenance?
    Skipping flushes leads to scale buildup, lower efficiency, more error codes, and shorter heater life.
  • Can I do this myself or should I call a plumber?
    Most homeowners can handle basic flushing and descaling with the right kit. If you’re unsure, call a pro—especially for your first time.
  • How do I know if my heater needs flushing?
    Watch for slow hot water, fluctuating temps, odd noises, or error codes (like “LC,” “E1,” or “11”).
  • Do I need special filters or softeners?
    If you have hard water, an inline scale filter or whole-house softener is highly recommended.

Conclusion

Regular maintenance is the secret to long-lasting, efficient tankless water heater performance. Invest in a flush kit, use a quality descaler, and consider adding a scale filter if you have hard water. With just a little effort each year, you’ll enjoy endless hot water and fewer repair bills. Ready to get started? Choose the top maintenance kits above, follow the step-by-step guide, and keep your system running like new for years to come!

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