Delime tankless heater

• 1). Shut off the electricity (or the gas, as applicable) to the heater. This is very important. You can tape the breaker to ensure no one turns it on while you are working.
  
  
• 2). Turn off the water supply (cold water intake) running into the heater using the isolation valve. If you can't shut down the supply of water with the isolation valve, you should consult a plumber.
  
  
• 3). Screw a hose onto the drain outlets for both the hot and cold water pipes for the heater. The hose from the hot water pipe goes into the bucket and the hose for the cold water pipe attaches to the output valve of the pump. Put the input hose for the pump into the bucket with the hot water hose.
  
  
• 4). Put the vinegar into the bucket, open the drain outlets on the heater, and turn on the pump. This will begin the vinegar circulating through the heater. Let it vinegar flow through the heater for one hour.
  
  
• 5). Turn off pump and let the vinegar drain from the heater and dispose of it so you'll have room in the bucket to flush the system. Remove the hose attached to the cold water drain and open the cold water intake to flush the heater. Let it run for five minutes.
  
  
• 6). Remove hose from hot water drain outlet and close it, make sure isolation valves are open. Run hot water from tap to test system. If operating properly, turn on power and test function of heater.