How often do you need to flush a tankless water heater? And how do you do it? A lot of people don't know that it's important to flush them appropriately and regularly so there is no scale build up. Turns out it's pretty simple. All you need is three gallons of distilled white vinegar, a submersible pump, bucket, and hose set. Make sure you turn off the gas first, leave the power on, and make sure the hot water valve and cold water valve is off. Be sure to check the pre-filter before anything else. In order to flush, you'll create a closed system loop with a hose to clear out all the sediment. Leave it on for an hour or so and you have a clean water heater. Watch the full video to learn how.