Can I flush my tankless water heater myself?

Flushing a tankless water heater is an important maintenance task that helps keep the system working properly by removing mineral deposits and sediment buildup. While some homeowners choose to have a professional perform this task, it is possible to flush a tankless water heater on your own if you are comfortable working with plumbing and follow the proper steps.

What is involved in flushing a tankless water heater?

Flushing a tankless water heater involves the following steps:

• Turn off the power and gas/water supply to the unit
• Disconnect inlet and outlet water lines from the unit
• Connect flushing adapters and hoses to inlet/outlet ports on the unit
• Connect the outlet hose to a drain or bucket to catch discharged water
• Use a pump, compressor or main water supply to push flushing solution through the unit
• Circulate flushing solution for 5-10 minutes or as directed
• Rinse out flushing solution by circulating clean water through the system
• Reconnect inlet/outlet lines and restore power and water supply

The process involves circulating a diluted acidic flushing solution through the heat exchanger and pipes to dissolve and wash away scale buildup and debris. After flushing, the system must be thoroughly rinsed with clean water to remove any residual flushing solution.

What equipment is needed to flush a tankless water heater?

Here is the equipment you’ll need to flush a tankless water heater:

• Flushing adapters/connectors to attach to inlet/outlet ports
• Hoses or tubing rated for high temperatures
• Pump, compressor or access to main water supply line
• Bucket or drain to discharge flushed water
• pH test strips to monitor flushing solution
• Goggles, gloves and other safety gear
• Commercial flushing solution or citric acid/vinegar

Flushing adapters allow you to connect hoses to the unit to circulate flushing solution. You’ll need a way to pressurize and propel the solution through the heat exchanger, either using a pump, compressor, or by connecting directly to your main water supply line. Have a drain or large bucket nearby to catch discharged water. Safety gear like goggles and gloves help protect you when working with flushing solutions. Use pH test strips to monitor the acidity of the solution during flushing.

What type of flushing solutions can I use?

There are two main options for flushing solutions:

• Commercial flushing products – Formulated specifically for flushing water heaters. Available as powders that you mix with water.
• Citric acid or vinegar solutions – A DIY approach using citric acid or household white vinegar mixed with water.

Commercial products such as Fernox Cleaner F3 or Sentinel X400 are ideal because they are designed for descaling. Follow the product instructions for the proper dilution ratio. Approximately 1 cup of citric acid or 2 cups of vinegar per gallon of water can be used to create a DIY flushing solution. The acidic solutions help dissolve mineral deposits. Use pH test strips to target an acidic pH between 4-5.

Step-by-Step Guide to Flushing a Tankless Water Heater

Follow these steps to flush a tankless water heater:

1. Turn off power and water supply – Locate the breaker for the tankless unit and turn it off. Then turn off the gas line and shut off the main cold water inlet valve.
2. Disconnect water lines – Disconnect the inlet and outlet water lines from the tankless unit so you can attach flushing adapters/hoses.
3. Connect flushing adapters & hoses – Use the appropriate fittings to securely connect flushing adapters and flexible stainless steel hoses to the inlet and outlet ports on the tankless unit.
4. Connect outlet hose to drain – Place the outlet hose in a floor drain or a large bucket to catch discharged water during flushing.
5. Prepare flushing solution – Mix up your commercial descaling product or DIY citric acid/vinegar solution per the instructions. Check that it reaches an acidic pH between 4-5.
6. Circulate flushing solution – Use a pump, compressor or water pressure to push the flushing solution through the tankless unit’s heat exchanger and pipes. Flush for approximately 5-10 minutes.
7. Rinse with clean water – Disconnect flushing tank and use fresh water to rinse out any remaining solution and flush the system for a few more minutes.
8. Reconnect plumbing – Remove flushing adapters and reconnect the inlet and outlet water lines. Restore power and gas/water supply to the unit.
9. Inspect & test – Power on the unit and inspect for leaks. Test to ensure hot water flows properly with no issues.

Follow all safety precautions when working with hazardous flushing solutions. Wear eye protection and gloves, and have adequate ventilation. Flushing your tankless water heater regularly will help prevent issues with mineral buildup and debris that can affect performance and lifespan.

Precautions When Flushing a Tankless Water Heater

Here are some important safety precautions to keep in mind when flushing a tankless water heater:

• Wear goggles, gloves, closed-toe shoes, and protective clothing
• Work in a well-ventilated area
• Follow manufacturer instructions for flushing solution concentrations
• Avoid splashing flushing solutions
• Securely connect hoses and adapters to avoid leaks
• Direct discharged water to a drain or container
• Neutralize and dispose of used flushing solution properly
• Keep flushing solutions out of reach of children and pets

Acidic descaling products require safe handling procedures. You want to avoid direct skin or eye contact. Having proper ventilation prevents breathing irritating fumes. Securely connecting the flushing rig helps minimize leaks. Safely disposing of used solution prevents environmental hazards. Take your time and exercise caution when DIY flushing.

How Often Should I Flush My Tankless Water Heater?

Most manufacturers recommend flushing your tankless water heater annually as routine maintenance. However, flushing frequency depends on water quality and usage:

• Annually is recommended for typical water conditions
• Every 6 months for hard water over 200 ppm
• Every 3-6 months for very hard water over 400 ppm
• More often for units heating over 5 gpm continuously

In areas with hard water, flushing twice per year can help prevent heavy limescale accumulation that impairs performance. Heating high flow rates also accelerates mineral buildup. Check your owner’s manual for any flushing recommendations specific to your tankless model. Performing an annual flush helps prevent issues and maximize the system’s service life.

Signs It’s Time to Flush Your Tankless Water Heater

Here are some signs that indicate it’s time to flush your tankless water heater:

• Decreased hot water flow rates
• Unit is slow to heat up
• Hot water temperature fluctuations
• Scale buildup visible in heat exchanger
• Overheating error codes
• Mineral deposits at faucet aerators
• Reduced heating capacity
• Higher energy bills

As scale accumulates, it impedes water flow through the heat exchanger. This reduces heating efficiency and capacity, resulting in problems like slow heating, temperature fluctuations, and error codes. Visible scale buildup, deposits at faucet aerators, and increased energy usage indicate time to flush. Catching buildup early maximizes effectiveness of flushing.

How to Clean a Tankless Water Heater Heat Exchanger

To clean the heat exchanger inside a tankless water heater:

1. Inspect the heat exchanger. Remove cover panel and use flashlight and mirror to look inside exchanger. Look for scale deposits or debris.
2. Obtain descaling solution formulated for tankless heat exchangers. Examples include Fernox DS-40 or Sentinel X400.
3. Connect pump and hoses to tankless unit to create closed-loop system.
4. Circulate descaling solution through heat exchanger for 15-20 minutes.
5. Rinse with fresh water for 10+ minutes to flush solution and debris.
6. Check heat exchanger again. Use soft brush to gently remove any remaining loose scale.
7. Restart tankless unit and test. Hot water flow should improve if exchanger is clean.

It’s important to use a descaling product specifically formulated for tankless heat exchangers and follow circulation times. Extending the contact time allows the solution to fully dissolve mineral buildup. A thorough fresh water rinse prevents corrosion. Soft brushing combined with flushing clears stubborn scale out of the exchanger. A clean heat exchanger optimizes hot water capacity and efficiency.

Table of Recommended Descaling Solutions

Descaling Solution	Mix Ratio (Solution:Water)
CLR Calcium, Lime, Rust Remover	1:3
Fernox DS-40 System Cleaner	1:4
Sentinel X400 Heat Exchanger Cleaner	1:1
Citric acid solution	1 cup per gallon
White vinegar solution	2 cups per gallon

When mixing your own citric acid or vinegar solutions, aim for a pH of 4-5 for maximum descaling capability. Commercial products like CLR, Fernox DS-40, or Sentinel X400 are formulated specifically for heat exchangers. Follow manufacturer’s suggested mix ratios when diluting with water.

Conclusion

Flushing your tankless water heater is essential preventive maintenance that can be performed by a DIYer with some plumbing skills. It involves circulating an acidic descaling solution to dissolve mineral deposits and improve heating efficiency. Flushing once a year is recommended, but frequency varies based on water hardness and usage. Descaling tankless heat exchangers requires proper products and procedures. With the right approach, flushing your unit can restore performance and prolong service life.