I've put this task on the back burner long enough and with cold weather anticipated next week, I have to add some boiler antifreeze to my heating system. I calculated the capacity of my entire closed loop system to be 7.7 gallons. Upon testing the system this summer, I smelled a bit of antifreeze but the test kit indicated freeze protection only to 32degF. I figure on pumping 2 gallons into the system should suffice. Mind you, I'll be tieing a wood boiler into the heating system in 2-3 months so I prefer to avoid a complete "drain" of the heating system. Can I do the following: 1. Shut the heating system down 2. Close the return valve and isolate the boiler from the remainder of the system. 3. Drain 2 gallons from the boiler and pump 2 gallons of glycol while purging the boiler 4. Then, open the zone valves/return valves while running the circulator a couple of minutes to mix residual water with the glycol?