There are several methods by which a valve drill can be completed, the important thing being that all valves can be reached and manipulated.

Method 1

Diver conducting the drill ensures that team is aware of his/her intention to conduct a valve drill

Check Back up reg with brief purge

Close Isolation valve fully whilst signalling team that you are closing a valve

Swap from primary regulator to back up

Close right pillar valve whilst signalling team that you are closing a valve

Re-open right pillar valve, ensure 2nd stage working by purge, swap back to primary

Swap light from left had to right

Close left pillar valve whilst signalling team that you are closing a valve

Re-open left pillar valve

Return light to left hand

Re-open isolation valve

Complete flow check on all valves to ensure open

Signal drill completed

Method 2

Diver conducting the drill ensures that team is aware of his/her intention to conduct a valve drill

Purge backup regulator to verify operation

Shut down the right pillar valve whilst signalling your team that you are closing a valve

Breathe down the primary regulator and swap to backup

Clip the primary regulator to right chest d-ring

Re-open the primary, unclip the 2nd stage and purge to verify operation

Switch from backup to primary

Close the isolator whilst signalling your team that you are closing a valve

Re-open the isolator

Swap light from left had to grasp in right

Close left pillar valve whilst signalling your team that you are closing a valve

Purge back up regulator

Reopen left pillar valve

Briefly purge backup reg to ensure working

Return light to left hand

Conduct a flow check to ensure all valves open

Signal drill completed

Both of these accomplish a complete shutdown of the entire system and with practice they can be completed quickly and with minimal movement in the water column. One of the key things to ensure is that the trim position of the diver in the water is correct. With good trim and positioning then valve drills become significantly easier.