We want to pass on our savings to our customers, so we've lowered the price of this item. However, since our price is now below the manufacturer's suggested retail price, we are restricted by the manufacturer from showing the price right away.
This is a convenient collection of off the shelf parts. It consists of a bucket (like the orange ones Home Depot sells) a Franklin UP16M 1/6 HP submersible pump and two washing machine hoses.
Add two gallons of white vinegar. Connect one hose from the pump to the cold service valve on your tankless heater and the other one from the hot service valve to drain back into the bucket. Set the valves and run for 45 min to an hour. That's it.
To purge the vinegar, relocate the "hot" hose to a drain and restore just the cold service valve to normal. Let it run for five minutes. Only then restore the hot valve to normal.