I see I have three return zone lines, used for draining and purging air. I wish to have each zone under my control in a cost conscious manner. I thought a thermostat in line v/v on each line before end of the lines where the drain valves are.
Each one of these would have its own thermostat control.thermostat on the wall and wires run to each new in line thermostat valve would be one way to do it. Is this accurate thinking and if so ,recommend a type, name or some identification so I could pre-order quality.refer to both the valve type or what's it called,name brand. I welcome qualified answers, suggestions from a knowledgeable person. Thank you, for time, thought, any replies

If I understand you here...

You want to use one circulator and 3 zone valves and 3 thermostats to separate and control 3 separate zones. The only real trick will depend on how the feeds are piped...to a point, right?

Taco or grundfos circulators both work great.

Taco zone valves are good/common zone valve in my area.

Am I on the right track here, or did I misunderstand you?

Mark