How to Choose Regulators and Pressure Gauges for Scuba Diving

A typical regulator reduces the pressure of the air in the tank in two stages so that, at the mouthpiece, it exactly matches the pressure of the water surrounding it.

Understanding regulators

A regulator is a device that allows you to breathe air from a tank. The modern two-stage scubadiving regulator valve is a relatively simple item of engineering. Its function is to reduce the pressure of the gas being delivered from the tank through the first-stage to around 8 bars (120 pounds per square inch, or psi) to 10 bars (150 psi) more than ambient pressure. It then reduces the pressure further, at the second-stage, to match the surrounding water pressure. In this way, there is virtually no effort to inhale. The regulator then has to allow the user to exhale the unused part of the inhaled gas. Exhaled air is simply bubbled out into the water. The idea is to make breathing as natural as possible.

Regulators vary in price considerably. You could be forgiven for thinking that the best performing regulator is the most expensive and that the cheapest is hard to breathe through, but this is not true. Unfortunately, there is no way of finding out which one is best before you buy – you can’t try a regulator in the shop. What you can examine is the specification of a regulator, its design features, what it’s made of and how well it has been finished.

Regulators employ either a diaphragm or a piston mechanism in the first-stage. In general, pistons give high performance but are less suitable than diaphragm designs for use in cold, fresh water since their working parts come into contact with water.

A balanced first-stage will keep demand pressure constant regardless of what the pressure of the air is in the tank, which means it will not be more difficult to breathe as the tank empties. Very cheap regulators tend to have unbalanced first-stages.

The second-stage is held in the mouth. Most mouthpieces are made from plastic because it is light. However, plastic does not have any heat-sink qualities (which would enable it to absorb heat). This is important if the diver intends to use the regulator in cold, fresh water. Some manufacturers add metal inserts to allow for this while others make the whole item from metal.

Some regulators have a breathing-resistance adjustment knob that can be used to vary the amount of effort needed to crack open the valve with the initial part of an inhalation.

The clean flow of air within the body of the second-stage can cause a venturi effect (which is what happens when wind increases velocity because of a constricted flow). This effect can make breathing easier, but it can also cause exponential free-flows under certain conditions. Some regulators have a venturi plus/minus switch that positions a vane within the flow to disrupt it.

The design and function of the purge valve can be crucial, too. It’s used to give a boost of air to clear water from the mouthpiece should it flood. The design of the exhaust T is important because you don’t want to have to look through a curtain of your own exhaled bubbles.

Regulators have ports that allow hoses for ancillary equipment to be fitted. One of these is the pressure gauge. It shows the pressure of air remaining in the tank and is used like a fuel gauge. Your instructor will teach you how to manage your air supplies.

Filed Under: Sports & Fitness


About the Author: Cody Riffel is a regular contributor to MegaHowTo. She likes to write on variety of topics, whatever interests her. She also likes to share what she learns over the Internet and her day-to-day life.

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