A bubble check is a simple underwater inspection that can reveal breathing-gas leaks before you commit to the dive. Your cylinder valve, first stage, and several hose connections are difficult to see once you're wearing your equipment, so having another diver look for escaping gas provides an additional opportunity to catch a problem.
It's a quick procedure, but an important one. A regulator can appear to function normally while a connection or hose is leaking, and discovering that problem in shallow water is considerably better than discovering it at depth.
When to Perform a Bubble Check
Perform a bubble check shortly after entering the water, before continuing to your planned depth. On a shore dive, that might mean stopping in shallow water where both divers can comfortably inspect one another. On a boat dive, it may require a brief descent to a shallow, agreed-upon depth where conditions allow the check to be performed safely.
The important thing is to perform the inspection early, while returning to the surface remains straightforward. A bubble check doesn't replace your pre-dive checklist or equipment function tests. It provides an additional inspection once the equipment is submerged.
How to Perform a Bubble Check
The procedure is straightforward. Each diver needs to remain reasonably still while the other looks for unexpected bubbles escaping from the equipment.
- Get into position. Stop at a comfortable, shallow depth where both divers can maintain control and inspect one another.
- Check the cylinder and first stage. Look carefully around the cylinder valve, regulator connection, first stage, and attached hose fittings.
- Inspect the remaining connections. Follow the regulator and inflator hoses, paying particular attention to fittings, hose ends, and the pressure gauge connection.
- Look for continuing bubbles. Give trapped air a moment to escape and distinguish ordinary exhaled bubbles from a persistent stream coming from a particular connection.
- Exchange roles. Once the first diver has been inspected, reverse positions and repeat the check.
If you find something suspicious, indicate where the bubbles are coming from rather than simply signaling that there's a problem. You can then return to the surface and investigate.
Not Every Bubble Is a Leak
It's common for air to become trapped in folds of a BCD or wing, beneath equipment, or around straps during entry. These bubbles may escape when you move or change position. They're generally harmless and should stop once the trapped air has been released.
A continuing stream from a pressurized connection is different. Cylinder and regulator O-rings, hose fittings, gauge connections, and damaged hoses are all potential sources of leaks. Some are small enough to be difficult to notice without deliberately looking for them, while others produce an obvious stream of bubbles.
The important distinction is whether you're seeing air that was temporarily trapped during entry or gas that continues escaping from the equipment. If you cannot determine the source underwater, return to the surface and investigate.
What If You Find a Leak?
I personally end the dive if I discover an unexpected leak in my equipment. Some divers are comfortable accepting a small amount of leakage, but I don't see a compelling reason to continue when I've identified a problem with my breathing-gas system before reaching depth.
Return to the surface, identify the source, and have the problem corrected appropriately before diving again. A damaged O-ring may be simple to replace, while a leaking hose or regulator component may require professional servicing. Don't assume a leak is harmless simply because it appears small.
Example of a Bubble Check
The demonstration below provides a useful example of what escaping gas can look like underwater. Notice how a continuing stream of bubbles can make an equipment problem visible even when the regulator appears to be operating normally. Animation courtesy of @jadescubaadventures on Instagram.
