How to Flush an AO Smith Tankless Water Heater in 5 Steps

To flush an A.O. Smith tankless water heater, turn off the power, connect a hose to the service valve, and run a descaling solution through the system.

Flushing your AO Smith tankless water heater is crucial for maintaining efficiency and preventing mineral buildup. Unlike traditional tank heaters, tankless models require descaling rather than full flushing. This guide provides detailed instructions to properly maintain your unit.

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Why Descaling Your AO Smith Tankless Heater Matters

Mineral deposits from hard water can reduce heating efficiency by up to 25% in tankless water heaters. Descaling removes these deposits, ensuring:

• Consistent hot water flow
• Lower energy bills
• Extended unit lifespan
• Prevention of costly repairs

For homes with hard water, consider installing a water filter for your tankless system to reduce mineral accumulation.

How Often to Descale Your Unit

AO Smith recommends descaling frequency based on water hardness:

Step-by-Step Descaling Process

1. Prepare Your Work Area

Gather these supplies:

• Descaling solution (white vinegar or commercial descaler)
• Submersible pump
• 2 buckets
• Hose kit
• Adjustable wrench
• Gloves and goggles

2. Enter Service Mode

To initiate the descaling cycle:

1. Press and hold the Power and ▲ buttons for 5 seconds
2. Display will show “SVC” indicating service mode
3. Unit will automatically begin the pump sequence

3. Connect the Flushing Kit

Follow these connection steps:

1. Turn off cold water supply valve
2. Attach hoses to service ports
3. Place pump in bucket with descaling solution
4. Connect outlet hose to drain bucket

4. Run the Descaling Solution

Allow the solution to circulate for 45-60 minutes. The process:

• Removes limescale deposits
• Cleans heat exchanger surfaces
• Improves heat transfer efficiency

5. Rinse and Restart

Complete the process by:

1. Flushing with clean water for 5 minutes
2. Disconnecting hoses
3. Restoring water supply
4. Pressing Power to exit service mode

Maintenance Tips Between Descaling

Extend time between descaling with these practices:

• Install a whole-house water softener
• Use a point-of-use water filter
• Monitor water pressure (should be 20-80 psi)
• Check for error codes monthly

When to Call a Professional

Contact an AO Smith certified technician if you experience:

• Persistent error codes after descaling
• Noticeable drop in water temperature
• Unusual noises during operation
• Visible leaks around connections

For complex HVAC maintenance, consider AO Smith’s professional service options or consult our guide on essential HVAC tools if you’re performing your own maintenance.

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