A regulator is a device with one end that attaches to the tank and the other end goes into your mouth that your breathe from. Basically, the function of a regulator is to take air that is stored at very high pressures and reduce it to the point that it can be breathed effortlessly when you inhale. The two sections of the regulator that accomplish this are the first stage and second stage.96px-Scuba_01

First stage

The first stage attaches directly to the tank. The first stage receives the high-pressure air from the tank and reduces it to an intermediate pressure and then delivers it to the low pressure hose that is attached to the second stage portion of the regulator, the part you breathe from. The primary function of the first stage is to maintain the intermediate pressure for the regulator system. This pressure remains constant and above ambient pressure regardless of how deep you go.


There are two types of first stages, piston valve and diaphragm valve. The piston valve is very basic and is comprised of a large piston and a spring. Piston regulators are very dependable and simple, but the inner parts are exposed to the water environment you’re diving in. The valve works by measuring ambient water pressure by allowing water to enter the valve area, which presses against one side of the piston. The other end of the piston is seated against high-pressure air in the tank. When you inhale, the intermediate pressure is reduced, and the piston moves allowing more air into the system, which maintains a constant intermediate pressure.

The diaphragm valves first stages are a little more complicated, but basically do the same thing as the piston valve. They measure the ambient water pressure but seal the parts from contact with the water by using a diaphragm. These valves have several moving parts. When you inhale, the intermediate pressure is reduced, and the diaphragm is bowed and pushes a poppet allowing more air into the system, which maintains a constant intermediate pressure. This type of regulator is not exposed to the water environment but is a more complex system.

Balanced and unbalanced regulators are other terms you need to understand when looking for a regulator. Balanced and unbalanced refer to the valves that make up the regulator. There are three types of valves: upstream, downstream, and balanced. Upstream and downstream valves seat directly against pressure from the tank. Downstream valves operate by opening via the high-pressure flow “downstream” of the airflow. Upstream valves open against the high-pressure flow “upstream” of the airflow. Balanced valves do not directly seat against the air pressure, which means they are not affected by pressure.

Unbalanced regulators use standard piston valves, which are downstream valves that depend on a certain amount of air pressure from the tank to operate properly. This means that as you deplete the amount of air in your tank, the pressure is reduced and the valve cannot maintain a constant intermediate pressure above the ambient pressure. Also, as you dive deeper, the ambient pressure increases, which makes it difficult for the valve to maintain a constant intermediate pressure above ambient pressure. Both of these, low tank pressure and deep diving, affect the regulator’s performance, making it harder to breathe.

Balanced regulators deliver air by a mechanical means and don’t require certain tank air pressures for performance. The air in the first stage is routed around both ends of the valve and removes the influence of tank air pressure. This type of operation means that the regulator performs the same regardless of tank pressure and depth.

Basically, there are three different types of first stage regulators: unbalanced piston, balanced piston, and balanced diaphragm. Once you understand these different types, determine the type of diving you’ll be doing, and determine a budget, you’ll be able to decide which is the best type of regulator for you.

Second stage

The second stage is the part of the regulator that goes in your mouth that you breathe from. It connects to the low-pressure hose that is attached to a low-pressure port on the first stage. The way it works is when you inhale, a diaphragm is bowed, which presses a lever connected to a valve. Whenever you inhale, air is delivered and the harder you inhale the more air is delivered.

When you exhale, a one-way flap valve opens allowing your exhaled air to escape without allowing water to enter. The exhaled air is routed below the mouthpiece and is dispersed as bubbles into the water.

The purge button on the second stage is used to purge water from your regulator. It operates the same valve that is used when you breathe.

Some regulators have fine-tuning adjustment knobs that are used to fine-tune the amount of air that is delivered when you breathe. Sometimes these are called venturi effect, air assist, etc. The adjustments are used to deliver air as easily as possible without the regulator free-flowing or delivering too much air.

When looking for a regulator, don’t just focus on price. Remember, this is your life support system and you should want the best that you can afford. Talk to your dive shop’s sales staff and ask if you can demo a regulator before buying one.

Other regulator requirements

Other than providing air for you to breathe, regulators also deliver air to other devices, such as an alternate air source, buoyancy compensator (BC), or dry suit. Regulators also provide an ability to monitor the pressure in your tank (submersible pressure gauge). The first stage of the regulator provides low and high pressure ports for the connection of the hoses for these devices.

The ports are openings that air can pass through. The high-pressure port is used to connect your submersible pressure gauge for monitoring the air supply in your tank. The low-pressure ports are used to connect an inflator hoses for a BC and dry suit and for connecting a backup alternate air second stage regulator.

Most regulators on the market today have up to two high-pressure ports and three to five low-pressure ports. The ports are marked on the first stage, so it’s easy to recognize which ports are which. Never connect a low-pressure hose to a high-pressure port.

Cost: $200 to $1500

Alternate air source

The alternate air source is a second stage that is connected to a low-pressure port on your regulator. It is used as a backup-breathing source for either you or your buddy to use in case of emergency.

This second stage is the same type of second stage on your primary regulator and works in the same manner. Typically though, the alternate air second stage is not usually designed with the fine adjustment knobs as the primary second stage. This helps to reduce the cost.

The alternate air second stage also causes drag when swimming underwater. Properly stowing this regulator and keeping it in a safe place helps to reduce drag and keeps it from dragging on the reef or getting caught on something.

Cost: $65 to $250

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