Maintaining Your Tankless Water Heater

Sediment is the silent killer of tankless water heaters. Unlike traditional tanks that store water, tankless units pass water through a heat exchanger with narrow channels; even a small amount of scale buildup can restrict flow, reduce efficiency, and force the unit to work significantly harder than it was designed to. Performing an annual flush keeps your system running at peak performance. It is a straightforward process that requires only a few basic tools and a bit of patience. When done correctly, this maintenance routine will extend the life of your heat exchanger by years, keeping your hot water supply consistent and your energy bills predictable.

  1. Kill the Power First. Turn off the electrical power at the breaker panel and shut off the gas supply valve if you have a gas-fired unit. Confirm the unit is off by checking the digital display or listening for the fan to stop running.
  2. Seal Off the Water. Locate the isolation valves on the plumbing lines leading to the water heater. Close both the hot and cold water supply valves to stop flow through the system.
  3. Release the Pressure. Open the drain caps on the service ports located on the isolation valves. Use a small bucket to catch the small amount of water that will spill out as you release the pressure.
  4. Prime the Pump. Attach one hose from your utility pump to the cold service port and place the pump inside a bucket filled with undiluted white vinegar. Attach a second discharge hose to the hot service port and run it into the same bucket.
  5. Let Vinegar Work Its Magic. Open both service port valves and turn on the pump. Let the vinegar circulate through the heater for at least 45 to 60 minutes to dissolve mineral deposits.
  6. Rinse Every Trace Out. Turn off the pump and remove the intake hose from the vinegar bucket. Place it in a bucket of clean, fresh water and run the system for 5 to 10 minutes to rinse out all residual vinegar.
  7. Bring the System Back. Close the service port valves, remove the hoses, and replace the drain caps. Open your main water supply valves and restore gas and electrical power to the unit.