Twinset Valve Drill

Twinset Valve Drill


The valve drill should be and in fact is easier to carry out in flat trim, with your head up and not moving!

Before jumping in make sure you haven’t got folds of drysuit or undersuit restricting movement, this should be obvious when doing a flow check!

Keep your elbow high and facing forward, arm brushing ear.

Do not drop your head in the movement


Order of Events


  1. Tell your teammates you are doing a drill – otherwise they may come and ‘help’ you
  2. Signal with light – emergency
  3. Quick purge left reg so you know working
  4. Close Right Post and Breathe reg down
  5. Switch to left post
  6. Clip off long hose Reg
  7. Close manifold
  8. Re-open right post and purge long hose reg so you know its working
  9. Switch light to right hand
  10. Close left post and breathe down – unclip right reg before you fully close
  11. Switch to long hose
  12. Open left post
  13. Return Light to left hand
  14. Open manifold
  15. Flow check (you and/or teammate/instructor)
  16. Check Gas pressure / gauge movement

 The mechanics of the drill are well demonstrated here by Style Diving although the order is a little different.






Is the gauge dropping when left side isolated? If so leak is left.

Breathe the bad side dead.

If you isolate a leaking cylinder with the manifold, breathe that one first, get as much from it as you can and save the non leaky cylinder for last.

If you suddenly seem to be using no gas you have left the manifold shut!





Matt Jevon, M.Sc. F.IoD is a Full Expedition level Trimix and Cave instructor on OC and CCR with TDI and ANDI. He is the JJ-CCR and Divesoft Liberty Sidemount instructor and dealer for Ireland. Matt’s personal diving has included cave exploration in the Philippines, wreck projects in Croatia and Ireland as well as being one of the inaugural dirty dozen in Truk! Matt has held accreditations as an interdisciplinary sports scientist, sports psychologist with BASES and was a British Olympic Registered Strength and Conditioning Coach and invitee on the Olympic Psychology Advisory Group. Matt works in high performance business as a board advisor and non-exec, high performance sport and is a partner in South West Technical Diving in Ireland. and writes the Facebook page Psychological Skills for Diving


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