Piping in new zone valves?

Danscrew said:

I'm installing 3 new zone valves in the return side of my hot water system. I would like to install Tee's with Boiler drains. To purge air from the system what side of the zone valve would be best ? Guessing before would work best since the valves are normally closed ? Please advise thanks Dan

I prefer zv on supply to prevent ghost flow in unopened zones

One valve at the boiler return can work well for a purge. Just open one zone at a time to purge 

Dan Holohan has an interesting piping arrangement he has called The Pumping Away Module 
 This is a section of piping that starts at the boiler supply riser. Then there is a tee fitting with a boiler drain followed by a full port ball valve. The next series of items in order is an air separator with expansion tank and fill valve components followed by the system circulator.  In your case you should add the zone valve manifold 
In this drawing there are no zone valves however there are 3 isolating valves on the return. These three valves stay closed while purging the boiler. Also close the full port ball valve in the supply. Attach a garden hose to the boiler drain on the tee fitting at the supply pipe just before the full port ball valve. Now add full house water pressure to the expansion tank and compress any air in the radiator loops. (The boiler is not connected to this high pressure)  

Now open the boiler drain and  one of those isolation valves on the return. This will force all the air down the piping and into the boiler, once in the boiler the water from that zone loop will fill the boiler and exit out the boiler drain valve at the tee fitting on the supply. Once you see water flow with no air, you know that loop is air free. Close that isolation valve on the return and allow the pressure to fully charge and compress any air in the system.