Free Flowing Regulator at Depth:
What to Do & How to Prevent It
A free-flowing regulator at depth is one of those situations that can rapidly go from annoying to dangerous, especially in cold water or when you're far from the surface. The risk of a complete gas loss is real, and every diver should know how to respond when it happens.
What Is a Free Flow?
A free flow occurs when your regulator delivers gas continuously and uncontrollably. Instead of air only flowing when you inhale, the second stage begins to vent gas non-stop. It can happen for a number of reasons:
- Cold water freeze-up (most common at depth)
- Debris or ice formation inside the second stage
- Over-pressurization due to a malfunctioning first stage
- Sticking purge button or cracked diaphragm
At the surface, a free flow wastes gas and is annoying. At 100 feet, it can drain your tank in minutes and be a real emergency.
What to Do If It Happens
If your primary regulator starts free flowing at depth:
- Purge briefly, then remove from your mouth to see if it resets (hold it in your hand, not clipped off).
- Try turning the second stage mouthpiece down to disrupt the flow.
- Try putting your finger over/in the mouthpiece to disrupt the flow.
- Switch to your alternate air source, or your buddy’s, if the free flow continues.
- Signal your buddy with a thumbs up (abort).
If you're using a long hose and have a necklace backup, switching regs is fast. Just stay calm and communicate clearly.
The Problem With "Free Flow Breathing" Training
Most open water courses teach a skill called free flow breathing, where you're supposed to sip air from a regulator that's continuously venting. You tilt the second stage so the bubble stream flows past your mouth, and you "sip" from the gas as it escapes.
This might work in a controlled pool, but at 80 feet in cold water, it’s a fantasy. You’re not going to hover calmly, sipping gas while your tank empties like a firehose. In real life, a diver faced with a free-flowing reg will instinctively switch to their alternate or their buddy’s reg. Not try to nurse a malfunctioning one.
The training exists to meet standards, but it shouldn't be your go-to plan. If your reg free flows at depth, treat it like an out-of-air scenario and get on backup gas immediately.
Why It Happens More in Cold Water
Cold water, especially below 50°F (10°C), dramatically increases the chances of a freeze-induced free flow. The process looks like this:
- Compressed air expands rapidly in the first stage, dropping temperature significantly.
- That cold air enters your second stage, where moisture from your breath can freeze the internal components.
- Ice holds the valve open, and the reg starts to free flow.
Prevention Tips
You can’t eliminate all risk, but you can reduce it:
- Use cold-water rated regulators environmentally sealed first stages and metal second stages are best.
- Avoid purging at depth unless necessary.
- Don’t test-breathe at the surface in freezing air wait until you're underwater.
- Keep your gear dry between dives to avoid water inside the reg body.
- Make slow descents to reduce temperature shock and freezing risk.
- Have a redundancy plan such as a pony bottle, or a reliable buddy.