[Trainer]

Joe, the Aqua Hot coolant tank has a 16 gallon capacity. The heating loops will be full of distilled water (2+ gallons) and do not need to be drained dry to properly flush the heating loops.

So you need 16 gallons of 50/50 engine antifreeze of your choice. Plus 16 gallons of distilled water to use in final flush after using 16 gallons of water from your hose for the first fliush.

You will catch 48 gallons of fluid during draining and flusihing.

The drain is through the floor near the back of the burner. I have used a large storage container with 5 or 6 inch sides so it will slip under the drain. As it fills, I have a Harbor Frieght 12 vdc pump that I use to pump it into 5 gallon buckets till the tank quits draining.

Your zone pumps do not prime themselves. So, you will drain the existing coolant, fill the coolant tank full with 16 gallons of hose water, use a raditor pressure tester to pump the tank up to 15 psi and run each of the zone pumps. Drain that and fill the coolant tank full with 16 gallons of distilled water. Use the pressure tester to prime your zone pumps again as you run them again. Drain that and fill the coolant tank full with 16 gallons of 50/50 engine coolant of your choice.

Lastly, use pressure tester to prime the pumps one last time and run them. You will know if the pump is primed as you can notice the return line flowing coolant from the pump(s) you are running.

Have fun!