Tankless water heaters are energy-efficient and long-lasting, but they need regular care. One of the most common questions is, “How often to flush tankless water heater?” It might seem like a small detail, but neglecting this maintenance task can lead to significant problems.
If you’re unsure when or how to flush your unit—or whether it’s even necessary—this guide covers it all.
Do You Need To Flush a Tankless Water Heater?
Absolutely, yes. Even the best tankless water heaters need flushing. Ignoring this task allows mineral deposits to build up inside your system.
What Happens If You Don’t Flush Your Tankless Water Heater?
Skipping flushing allows scale and sediment to coat the heat exchanger. This makes the unit work harder and overheat more easily. Over time, efficiency drops, and damage sets in.
How Do I Know If My Tankless Water Heater Needs To Be Flushed?
Signs of Mineral Buildup
White flakes or chalky residue around fixtures? That’s a red flag. It means hard water minerals are circulating through your heater.
Decreased Hot Water Pressure or Temperature
Flushing may be overdue if your hot water isn’t as warm or steady as before. Buildup restricts water flow and heat exchange.
Increased Energy Bills
When your heater works harder to produce hot water, it consumes more energy. If your bills suddenly spike, it’s time to check your unit.
How Often To Flush Your Tankless Water Heater
Knowing how often to flush tankless water heater depends on how much you use it and your water quality.
General Guidelines Based on Usage and Water Quality
Heavy Usage or Large Households
Flush your system every 6 to 9 months. The more hot water you use, the faster the scale builds up.
Hard Water Areas
If your home has hard water, aim to flush it every 6 months. You might also consider a water softener.
Soft or Filtered Water Systems
If you already treat your water, you can flush once a year to stay safe.
Light Usage or Seasonal Homes
Homes used occasionally or with only one or two occupants can flush every 12 to 18 months.
How Often Should I Flush My Tankless Water Heater If I Have A Water Softener?
With soft water, flushing once a year is usually enough. Still, check the manual or consult your installer.
Should I Flush My Tankless Water Heater After 5 Years?
Yes, especially if it hasn’t been flushed before. Five years of buildup can significantly reduce performance.
Should You Flush A Water Heater That Has Never Been Flushed?
Definitely, it’s better late than never. Even older units benefit from flushing—it may extend their lifespan.
How To Flush A Tankless Water Heater
If you’ve been wondering how to flush a tankless water heater, here’s a simple overview.
Turn Off Power and Water Supply
Shut off the gas or electricity to the unit. Also, the water valves must be closed to stop flow during the process.
Connect the Flush Kit
Attach hoses from your flush kit to the service ports. Make sure the hoses are secure to avoid leaks.
Add Cleaning Solution
Use a descaling solution made for tankless systems. Avoid using vinegar or random cleaners—it could void your warranty.
Run the Flush Pump
Depending on the buildup, the pump circulates the solution through the heater for 45 to 60 minutes.
Rinse and Reconnect
After flushing, run clean water through the system to rinse out any residue. Remove the hoses and restore connections.
Can I Flush My Own Tankless Water Heater?
Yes, but only if you’re confident working with basic plumbing and have the right tools.
When to Call a Licensed Plumber Instead
You’re Not Comfortable Working With Gas or Electrical Connections
Safety first. If you’re unsure, call a professional.
The Unit Hasn’t Been Flushed in Years
A neglected system may need inspection and more detailed cleaning.
You Notice Error Codes or Performance Issues
These signs may point to deeper problems that flushing alone won’t fix.
You Own a High-End or Commercial System
Some complex units need expert handling. Don’t risk damage or warranty issues.
You Want to Protect Your Warranty
Many manufacturers require professional services for coverage. Always check your warranty terms.
How Long To Flush a Tankless Water Heater
Average Flushing Time for Most Units
Flushing usually takes 60 to 90 minutes, including setup and rinsing. The flush itself runs for about 45 minutes.
Factors That May Affect Flushing Duration
Amount of Mineral Buildup
Heavily scaled units may take longer to clean thoroughly.
Unit Size and Flow Rate
Larger units or those with higher flow rates might need extra time to ensure proper descaling.
Maintenance Tips to Prevent Frequent Flushing
Install a Pre-Filter or Water Softener
These devices catch minerals and debris before they enter your system. This reduces the need for frequent flushing.
Schedule Annual Inspections
A quick yearly check can catch early signs of buildup, leaks, or part failure.
Monitor Performance Metrics
Watch your water temperature, pressure, and energy bills. Changes can be early clues that it’s time to flush.
FAQs
Should I Flush My Tankless Water Heater After 5 Years?
Yes. Even if it’s never been flushed, doing so now can help restore efficiency and extend its life.
Should You Flush A Water Heater That Has Never Been Flushed?
Yes, flushing removes harmful buildup and may improve water quality and performance.
How Often Should I Flush My Tankless Water Heater If I Have A Water Softener?
Once a year is usually enough for softened water. Still, monitor for signs of scaling.
How Long To Flush A Rinnai Tankless Water Heater?
Rinnai systems typically take about one hour to flush. Always follow the manufacturer’s instructions for best results.
Trust the Pros at Advanced Plumbing & Drain in San Francisco, CA
Now that you know how often to flush tankless water heater systems and how to flush a tankless water heater, don’t wait for trouble to start. A little maintenance now can save you a lot of money later.
Whether you’re worried about how long to flush tankless water heater units or wondering, “Do you need to flush tankless water heater systems that are brand new?”, the answer is simple—yes, and it’s worth it.
Let the professionals handle it the right way. Advanced Plumbing & Drain in San Francisco provides top-tier tankless water heater services. We’ve got your back from flushing and repairs to complete system replacement.
Call us today or book online. Clean, hot water is just a flush away!
Meet Our Founder: Nick, Master Plumber & Owner
Nick is the owner of Advanced Plumbing & Drain, bringing years of professional plumbing expertise to the San Francisco Bay Area. Driven by core values of integrity and exceptional craftsmanship, he leads a fast-growing team specializing in comprehensive residential and commercial repairs, drain cleaning, and water heater solutions. Nick is dedicated to ensuring every job is completed right the first time, earning long-term trust across San Francisco and San Mateo County.
