The valve drill stands as one of the most fundamental yet misunderstood skills in diving - often dismissed as a technical diver’s ritual or reduced to a test of speed. But in reality, mastering the valve drill transcends certification levels and kit configurations. Whether you dive twinset backmount or sidemount, whether your dives take you to 15 meters or into caves at 60 meters, this skill is central to your safety, awareness, and capability as a diver.
At its core, the valve drill is not an emergency procedure - although it will serve you well in emergencies. Rather, it's a deliberate practice session designed to engrain your muscle memory, deepen your understanding of your equipment, and cultivate a calm, controlled response to gas failures. It simulates potential valve-related problems and offers you a controlled space to rehearse the response - so that when something does go wrong, your reaction is second nature.
Different training agencies teach slightly different versions of the drill. But the precise order or hand technique is less critical than the principle: You must be able to confidently manipulate all valves, switch regulators appropriately, prevent gas loss, and keep breathing throughout the process.
Let’s explore the drill step-by-step, including the rationale behind each action and the key details that make this skill effective and safe.
Before beginning the drill, perform a brief purge of your backup regulator. This ensures it's pressurized and functioning, confirming that you have a second source of breathable gas available when you switch over.
Signal to your teammate(s) that you’re about to begin the drill. This is often done using your primary dive light. Clear communication is vital; your teammate should be stationary, alert, and ready to assist, particularly in case of an accidental gas cutoff.
Step 3: Right Post Shutdown
Begin by closing the right post, which typically supplies gas to your long hose regulator (your primary). Once the valve is fully shut:
- Breathe down the remaining gas in the hose until it is empty.
- Switch to your backup regulator (which should now be your only source of gas).
- Secure your long hose by stowing it on your right shoulder D-ring to prevent entanglement or confusion.
This step simulates a right post failure and trains you to switch to your backup seamlessly and stow gear appropriately.
Step 4: Reopen the Right Post
After waiting a few seconds (to simulate assessment time), reopen the right valve. Begin the turn slowly - many first-stage regulators have O-rings that can dislodge if opened too quickly, resulting in leaks or failure. Once open:
- Purge the long hose to verify gas flow.
- Detach it from the D-ring so it’s ready for use or gas donation if needed.
Next, move to the manifold isolation valve. This valve connects your two cylinders in a twinset and allows gas to flow between them.
- Signal your teammate before manipulating the valve.
- Shut the isolation valve carefully. This will isolate the left and right cylinders but should not cut off your breathing gas - both first stages remain supplied.
- After a few seconds, reopen the manifold valve using gentle force. Avoid over-tightening or aggressively opening/closing the valve. Too much torque can damage the valve or make it difficult to operate underwater.
This stage trains your ability to isolate a leak and reconnect cylinders in a controlled manner.
Step 6: Left Post Shutdown
Now close the left post, which supplies gas to your backup regulator. This step is critical - it's where divers are most vulnerable because they’re now depending on gas from the previously tested long hose.
- Hold your light in your right hand, but not with a Goodman handle - instead, grip it in a way that allows you to drop it quickly should you need to share gas.
- After closing the left valve, breathe down the gas until the regulator delivers no more air.
- Switch back to your long hose regulator.
Once the backup is drained and you're back on your long hose:
- Wait a few seconds, then reopen the left post with care, again rotating the valve slowly to prevent unwanted freeflows.
At this point, all three valves (right post, left post, manifold) should be open and the system should be fully operational. Verify this by performing a systematic flow check:
- Check the right post – confirm full open and purge the long hose.
- Check the manifold valve – confirm open with a gentle twist.
- Check the left post – confirm full open and purge the backup.
After verifying gas delivery on both regulators, check your SPG and communicate your remaining pressure to your teammate. This closes the drill with awareness and mutual understanding of gas status.
- Never turn a valve aggressively - always initiate the turn slowly to avoid damaging components or causing a freeflow.
- Maintain team positioning and awareness throughout the drill. Your teammate should always be in position to donate gas immediately.
- Stay calm and focused - if you get confused or shut off the wrong post, don’t panic. Signal out-of-air, regain your breathing gas, then calmly reconfigure.
- Avoid treating this as a race. Fast doesn’t mean good. Understanding what you're doing - and why - is far more valuable than speed.
