This is the setup I have:

My Adaptor works fantastic:

1. Water Supply Valve (in basement) closed.
2. Adaptor attached to Hose Bib #3.
3. Air Compressor set at 50-60 psi.
(I have a belt-drive compressor with max air flow 9 GPM at 50 psi, which is adequate).
4. I use the Blue Valve downstream of the Back Flow Preventer for control (On-Off). This is to keep pressure inside the BFP at 50 psi to prevent to floater from dropping down.
If you shut the Valve upstream of the Back Flow Preventer, pressure will drop and the floater will come down, making your winterization job much harder (air leaks out the top of the BFP).

5. Bleed each circuit 2-3 x with 6-8 min each.
6. Give the compressor sometime to cool off between runs.
7. When done, all valves (Testcocks, Blue Valves x2) set at 45 degrees.

- BFP covered in ziploc bag for winter.
- Hose Bib opened for drainage.
See you in the Spring!!!