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Scuba Regulators


scube regulator
Your scuba regulator is the link between you and the breathing gas in your tank. It is one of the most important pieces of scuba diving equipment. Today’s regulators are marvels of compact, reliable, and durable design. We’ll look at the three main aspects of the scuba regulator: the first stage, the hoses and gauges, and the second stage.

The First Stage

The regulator first stage is the piece that mounts on the tank valve. It’s called the first stage because it’s the first part of the scuba regulator to handle gas from the tank. Its job is to step that high-pressure gas (at 3000 psi or more) down to a safe working pressure (around 145 psi), usually called the “intermediate pressure.”

First stages can use one of two methods to create the intermediate pressure: a piston or a diaphragm. Piston designs allow water to push a piston against spring pressure. They are generally less costly and easier to service, as they have fewer parts. However, piston designs are harder to adjust or “tune” and since they’re open to the water they are more prone to problems such as cold-water freeze-up.

Diaphragm designs are sealed–no water can enter the first stage. The ambient water pressure is transmitted to the inside through a flexible diaphragm. They are more expensive than piston designs, but are easier to adjust. And they work better in silty or very cold water, because the water is never in contact with the internal parts.

First stages can also be either balanced or unbalanced. The unbalanced design uses tank pressure to assist it in “cracking open” the gas flow. It typically delivers gas to you less easily as the pressure in the tank gets low. The intermediate pressure falls, increasing your breathing effort. This is most noticeable when you’re deep or breathing hard, and modern designs have reduced the increased effort noticeably.

The balanced design can maintain an ideal intermediate pressure regardless of tank pressure, and is the preferred design for deep or working dives. Balanced scuba regulators are also generally more expensive than unbalanced ones.

How the first stages connects to the tank valve is important, and again there are two designs: yoke and DIN. The yoke system is almost universal on the common AL80 tank (Aluminum, 80 cubic feet nominal). The DIN (named for Deutsche Industrie Norm, the German manufacturing standards) system is more compact and more secure than the yoke. DIN first stages screw into a threaded opening in the valve, and are designed to handle higher pressures than the yoke system. Steel tanks often have DIN valves, although either valve can be installed on any tank.

Compactness is nice to have in a first stage, as it sits behind your neck or lower back (depending on how you carry your tank) and you want to be able to bend your head back without hitting the first stage.

And when comparing first stages check how many ports they have. There are two types of port, High Pressure and Low Pressure. The HP ports dispense gas at tank pressure, while the LP ports dispense gas at intermediate pressure. At a minimum, you need one HP port (for your pressure gauge) and three LP ports (for your two second stages and the BC inflator). Having more ports gives you more choices when it comes to attaching and routing your hoses. Two HP and four LP ports is generally enough.

Finally, the first stage needs a dust cap. This covers the inlet opening when the regulator is removed from the tank. It keeps water and dust out of the first stage.

Hoses, Gauges, and Computers

Hoses come in two varieties, high-pressure and low-pressure, to meet the demands of both port types. It’s almost impossible to confuse them, as the two ports use two different thread sizes, but they’re also conspicuously labeled. They’re available in almost any length you like, and in a range of colors. Of course, black is the standard color, but for a few dollars more you can make a statement.

If you’re using analog gauges you have a submersible pressure gauge (SPG), a depth gauge, and often a compass, all mounted together in a console. The SPG connects to a high-pressure hose so it can measure your tank pressure. The console is typically clipped to a spot of your choosing on your BC, sometimes with a retractable lanyard.

If you’re using a dive computer, it can replace the depth gauge in the console or it can be worn on your wrist. Air-integrated computers also replace the SPG. They can be hose-mounted (still reading tank pressure from the HP hose) or they can be “hoseless” and communicate with a small transmitter mounted on one of the first stage’s HP ports. This allows you to get rid of the console entirely (and the HP hose) and wear a computer and a compass on your wrists.

Your BC inflator needs a hose, too. The LP hose for your BC ends in a quick-release connector which mates to the BC’s inflator assembly. And drysuit divers need another LP hose for the drysuit inflator valve.

The Second Stage

The regulator second stage delivers air to you whenever you breathe in. Its basic principles are the same as when it was invented by Cousteau and Gagnan in 1943. The second stage is a “demand valve” which opens when you create a small vacuum in your lungs and mouth, and closes once you stop breathing in. It delivers air to you at the same pressure as the surrounding water.

The mechanism is actually quite simple, although modern designs and materials have dramatically reduced the effort of breathing underwater. Modern second stages are designed to “fail open.” If the mechanism jams or fails, it will nonetheless deliver a constant stream of air.

Second stages use replaceable mouthpieces. Custom mouthpieces, including ones you can mold and heat-set, are widely available. A good-fitting mouthpiece is held lightly by the lips, not clenched in the teeth, and should be hardly noticeable in use.

The second stage will have a purge valve, which is used to clear water from the air chamber if the reg comes out of your mouth underwater. It usually has a small “dive/pre-dive” lever which helps control free-flows when on the surface. (A free-flowing second stage won’t stop delivering air–your scuba training will cover what causes free-flows and how to prevent them.) Some higher-end second stages also feature a knob which allows you to fine-tune the breathing effort it requires.

In addition to the primary second stage, divers today almost universally carry a second second stage. You’ll hear this referred to as a “backup,” an “alternate,” or an “octo.” It’s there for you should your primary second stage fail (unlikely), or to allow you to share air with your buddy or another diver who is out of air (a bit more likely). The term “octo” is short for “octopus,” a colorful description of the entire scuba regulator with its four hoses, coined by early divers who were used to just one hose (they used no BC, no pressure gauge, and no backup). The octo is often less expensive than the primary second stage. It needs to be stowed somewhere on your BC so it’s not dragged across the bottom while you’re scuba diving.

Other Features

As you might expect, scuba regulators are available in a mind-boggling array of prices, styles, and options. Selecting the right one for you requires, first off, knowing what sort of diving you’ll be doing. The right regulator for relaxed warm-water sightseeing is not the right regulator for deep cold-water dives. A dive shop is a good place to start asking questions. My advice is to try a variety of regulators on actual dives, and get a sense of where your diving might lead you, before you try to choose which scuba regulator to buy. It’s difficult to judge how well a regulator breathes until you’re in the water with it.

Some first stages now feature a mechanism which automatically closes the inlet opening when the regulator is removed from the tank, which means that if you forget to put the dust cap on your first stage is still protected. Ease of breathing is of course an important feature, with the easiest-breathing regs usually more expensive. Freeze-up protection is important for diving in very cold water.

Most of today’s scuba regulators come “nitrox-ready” out of the box. They are manufactured and assembled so that they can be used with recreational nitrox mixes (up to 40%). Nitrox is gas with more than oxygen than air (air is 21% oxygen). Nitrox gives you more dive time underwater at recreational depths, and is increasingly available and popular at dive resorts worldwide.

Scuba Regulator Maintenance

We’ll conclude with just a few words on keeping your regulator working. Regular service is important. Some shops include lifetime maintenance with regulator purchase, although parts are usually not included. Annual inspection with semi-annual rebuild, to replace the parts that wear out, is common.

You can keep your scuba regulator in top shape by cleaning it after use. Secure the dust cap and rinse the reg in clean fresh water. If you’ve been diving in salt water, a half-hour soak in warm tap water is good after your last dive of the trip, to dissolve away any salt crystals. Wipe hoses down with a light spray of silicone to keep them supple. Don’t store the regulator with sharp turns in the hoses–if possible, let the hoses hang down from the first stage, or coil everything loosely. If you’re not diving for a while, storing the regulator in a closed bag will keep ozone and other harmful fumes from degrading the synthetic parts.

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