How to Flush a Tankless Water Heater (Knoxville Homeowner Guide)
Tankless water heaters are known for efficiency—but they still need maintenance.
If you live in Knoxville or surrounding areas with mineral-heavy water, annual flushing is essential to keep your system running properly.
Here’s what homeowners need to know.
Why You Need to Flush a Tankless Water Heater
Over time, minerals from your water build up inside the system.
If not flushed, this can lead to:
Reduced efficiency
Lower water pressure
Inconsistent hot water
Shortened system lifespan
Routine flushing helps prevent costly repairs and keeps your unit performing the way it should.
How Often Should You Flush It?
Most homes should flush their tankless water heater:
Once per year (minimum)
More often if you have hard water
What You’ll Need
Non-corrosive descaling solution (or vinegar)
Submersible pump
Two hoses
Bucket
Gloves and eye protection
Step-by-Step: Flushing a Tankless Water Heater
Step 1: Turn Off Power and Gas
Shut off power to the unit (and gas, if applicable).
Step 2: Shut Off Water Supply
Close both the hot and cold water valves connected to the heater.
Step 3: Connect Hoses
Attach hoses to the service ports:
One for cold water inlet
One for hot water outlet
Both hoses should lead into a bucket.
Step 4: Set Up the Pump
Place the pump inside the bucket with your flushing solution.
Connect the pump to the cold water service port.
Step 5: Circulate the Solution
Turn on the pump and let the solution circulate through the system for 45–60 minutes.
This breaks down mineral buildup inside the unit.
Step 6: Flush with Clean Water
After descaling, run clean water through the system for about 5 minutes to clear any remaining solution.
Step 7: Disconnect and Restore System
Close service valves
Remove hoses
Reopen water supply
Restore power and gas
Step 8: Check for Proper Operation
Turn the system back on and check:
Water temperature
Flow
Any leaks
When You Should Call a Professional
Flushing a tankless system isn’t always a DIY job.
Call a plumber if:
You’re unsure about the setup
Your system hasn’t been serviced in years
You notice low pressure or inconsistent heat
You don’t have the proper equipment
Improper flushing can damage the unit or void warranties.
Tankless Water Heater Maintenance in Knoxville, TN
Friendly Neighborhood Plumber provides:
Tankless water heater flushing
Maintenance and inspections
Repairs and replacements
We make sure your system is running efficiently and safely.
Need Help Flushing Your Tankless Water Heater?
Call or text 865-443-7617
Visit 865FNP.com
Tankless Water Heater Questions Knoxville Homeowners Ask
Can I flush my tankless water heater myself?
Yes, but only if you’re comfortable with the process. Many homeowners choose professional service to avoid mistakes.
What happens if I don’t flush it?
Mineral buildup can reduce efficiency, damage components, and shorten the system’s lifespan.
How long does a flush take?
Typically 45–60 minutes for descaling, plus setup and rinse time.
Is vinegar safe to use?
Yes, many systems can be flushed with vinegar, but always check manufacturer recommendations.
Who services tankless water heaters in Knoxville, TN?
Friendly Neighborhood Plumber provides maintenance, flushing, and repair services throughout Knoxville and surrounding areas.
