When selecting regulators for cave diving, there are many features to consider. There is one feature, however, which can prove critical in a gas-sharing situation. It’s vital you understand what this feature is and why it’s important.
A matter of orientation
When you see dive equipment displayed on a manufacturer’s website, it invariably appears as though it is being worn by someone who is standing upright. When divers achieve horizontal trim underwater, what is at the top of the product photo is actually what will be directly in front of the diver. Similarly, what is at the bottom of the product photo points to what will be behind the diver.
In cave diving, the normal procedure for gas sharing is to put the out-of-air diver in front of the donor. There is at least one exception to this which we will cover in another article. Still, we generally put the out-of-air diver in front.
Doing so helps prevent the donated second stage from being pulled from the receiver’s mouth accidentally. It also helps the donor keep on eye of the affected buddy.
If you envision a dual-orifice manifold with a first stage attached to the right post, it means the hose going to the out-of-air diver needs to point upward, not downward as it normally does.
The same principle applies to sidemount. Where we normally start by running the long hose down the side of the bottle, when deployed for gas sharing, it needs to point in the opposite direction.
So what’s a turret?
In diving, the term turret refers to a rotating assembly containing all of a first stage’s low-pressure ports. Unless something like a tank valve gets in the way, turrets are typically capable of rotating 360° with no reduction in gas flow.
Atomic, Dive Rite, Hollis, Scubapro and Sherwood, among others, all offer regulator models with low-pressure turrets.
In a fix
Those regulator first stages which do not have turrets instead have what we call fixed low-pressure ports. These only point in one direction. Regulators with fixed low-pressure ports have fewer moving parts and are less costly to produce. They generally sell for less.
Fixed low-pressure ports are fine for recreational diving and in some cases are even desirable. For cave diving, however, they can cause problems.
As this photo shows, the norm when attaching first stages with fixed low-pressure ports is to start by having all hoses pint straight down.
- The good news is, doing this helps prevent hoses from blocking access to valve turnwheels.
- The bad news — or at least some of the bad news — is this can result in having to make some sharp bends, increasing strain on the hose.
But, in the words of the immortal Billy Mays, “Wait! There’s more…” This comes into play when you have to donate air to another diver.
As this illustration shows, passing the long hose to an out-of-air diver necessitates making a 180° bend in the hose. This causes two problems.
- To start, the bend can consume up to 30 cm/12 in or more of hose length. This can make it harder to share gas.
- Worse, this bend increases the possibility of hose kinking — especially when using braided hoses. Imagine being an out-of-air diver breathing off a donor’s long hose. You are under enough stress as it is. What happens when your gas supply suddenly cuts off?
Why turrets are better
When you pass a long hose to an out-of-air diver while using turret first stages, the hose rotates freely to point in the direction of the affected diver. No lost length. Less possibility of kinking.
By the way, the reason most cave divers angle their first stages down slightly is to make the isolator turnwheel easier to access. (At least when the long hose is not deployed.)
An added bonus
In addition to the low-pressure ports along the side of the turret, most such regulators have an additional port at the top of the turret.
This is a good place to attach low-pressure inflator hoses. It allows you to pass a long hose to an out-of-air diver while putting only minimal strain on the other low-pressure hose.
And now you know
If you are in the market for regulators for cave diving, by all means, seek out ones with rotating turrets. Anyone who is depending on you for emergency breathing gas will thank you.