How Does A Scuba Regulator Work?

We all like blowing bubbles, but how much do we actually know about the mysterious piece of equipment that allows us to do so?

As scuba divers, our scuba regulators are one of the most complex pieces of equipment we use.

Simply put, a scuba diving regulator is what delivers ambient pressure air, allowing us to breathe underwater.

However, in order to understand what a regulator does, we’ll have to understand the process of which the high pressure air in our tank moves through hose and finally delivers air at ambient pressure to us.

With every breath, this whole process runs through the scuba diving regulator setup, which includes numerous parts in addition to the actual regulator that delivers the air – the second stage.

🤔 1. Why Do We Need A Scuba Diving Regulator?

I’m sure you’ve turned on your tank valve and let the air out. The tank pressure is so great, that the noise it makes often wants to make you cringe!

The high pressure air that is stored in the tank is 3000 psi/200 bar, while the air we breathe at sea level is 14.7 psi/1 bar.

Now imagine breathing that air pressure right into your lungs. That’s not going to be a good idea!

The goal of the scuba regulator set is for the first stage to convert the high pressure in the tank first to intermediate pressure that goes through your low-pressure hose.

After which, the intermediate pressure gets further converted into ambient pressure which we can easily breathe.

Young scuba diver checking the scuba diving regulator

🔧 2. Parts Of A Scuba Diving Regulator Set

When talking about a “scuba diving regulator”, some refer to the actual regulator, the second stage, while others refer to both the first and second stages, connected by a hose.

Even more people refer to a regulator set as the complete package, together with the:

  • Alternative air source, otherwise known as the octopus
  • Submersible pressure gauge that will show you your depth and tank pressure
  • Low pressure inflator hose, which pumps air into to the BCD

First Stage

The first stage enables the connection of your tank to the rest of your regulator setup. The first stage has multiple ports – one or two high pressure ports, and some low pressure ports.

The high pressure port links to your submersible pressure gauge (SPG), and some first stages might have an additional port for the transmitter if you have an integrated air dive computer.

The low pressure ports link to your LPI to inflate your BCD, second stage regulator, and octopus.

The job of the first stage is to reduce the high tank pressure to an intermediate pressure of about 120 to 150 psi / 8 to 10 bars.

There are two types of fittings that affixes your first stage onto your tank valve – the DIN and yoke fittings.

DIN vs. Yoke


The DIN valve is named after the Deutsche Industrie Norm, an agency based in Berlin that first made the 5/8 inch threaded valve. The high pressure o ring is fixed as part of the DIN valve, as opposed to the tank valve like you normally see in yoke fittings.

With its higher pressure capacity, this type of valve is favored by commercial and technical divers.


The yoke valve is more commonly used in dive centers all around the world, connecting millions of recreational divers with their tanks.

While tech divers need a higher cylinder pressure, often as high as 300 bar, the yoke valve will work just fine in recreational diving.

Pro tip: Unless you have a specific need for a DIN valve, always go for yoke, or you’ll have to bring around a DIN-to-yoke adaptor, as most tanks have a yoke fitting.

Components of a scuba diving regulator

Second Stage or Primary Regulator

Here’s the most important part of your setup! An inferior scuba regulator can end up causing greater breathing effort, especially as the tank pressure drops, or worse, start to free flow when you’re 30 meters down.

Just like your first stage that was built to receive high pressure and convert it to intermediate pressure, the job of the second stage is to convert intermediate pressure to ambient pressure which you can breathe.

Intermediate pressure is kept at 120 to 150 psi / 8 to 10 bars, and the job of your second stage is to convert that pressure into breathable pressure, which is 1 bar at sea level and increases by 1 bar for every 10 meters you descend.

The second stage is a demand valve regulator that will deliver air only when required. If the diver stops inhaling, the regulator will no longer deliver air.

Low Pressure Hose

The first stage converts high pressure air and pushes it into your LPI through a low pressure port. The LPI then fills your BCD through the inflator hose button.

🌊 3. Different Types of Scuba Diving Regulators

Not all regulators are created equal! There is a distinct difference between buying an entry level regulator for $300 or a top-quality regulator for $1,500.

Note that cheap doesn’t mean unreliable. Regulator technology has gotten so good that even the most affordable regulators will function reliably underwater.

The key difference in quality tends to affect other factors such as breathing effort, performance in cold water and depth, the efficiency of air flows, and placement of the exhaust valves.

Balanced vs Unbalanced Regulator

The primary difference between a balanced and unbalanced regulator is the effect that it has on breathing effort, especially at depth, or when the tank pressure is running low.

Balanced Regulator

Very broadly, a balanced second stage will deliver the same amount of air regardless of the depth you are at or at different tank pressures.

A balanced second stage will equalize pressure on both sides of the air valve to compensate for depth and the decreasing tank pressure, and helping your breathing effort will remain consistent throughout your dive.

Balanced regulators are thought of as higher quality as unbalanced, and as a result, cost more.

Unbalanced Regulators

As the cylinder pressure drops, the breathing effort from the second stage often gets harder with unbalanced regulators.

You might struggle to pull a breath as you descend and the ambient pressure around you increases.

Piston vs Diaphragm Regulators

This affects how the high pressure air is let into the regulator system through the first stage. When open the cylinder valve, how the first stage delivers the air depends on whether it is piston or diaphragm.

Piston versus diaphragm regulator

Piston Regulators

Piston regulators have a piston (big surprise!) that moves up and down, controlled by a powerful, tensioned spring.

When you have the tank valve open, the piston moves to allow the air through.

Piston regulators are simpler and more basic with less moving parts. In addition, servicing and maintaining them tend to cost less.

However, there is a possibility of freezing up in extremely cold water temperatures, causing free flows and the regulator to fail.

Diaphragm Regulators

Diaphragm regulators contain a thick rubber piece called, you guessed it – the diaphragm!

A spring pushes the diaphragm from the opposite side, holding it closed. When air pressure enters the regulator, the spring gives, the gas to flow through the regulator and into a diver’s mouth.

Diaphragm regulators have more moving parts and are a more resistant to cold and water. They are also easier to keep clean as the internal parts are less exposed to the contaminants from the water.

🔍 4. Other Features Of Your Second Stage Regulator

While most standard regulators are pretty similar, there are some subtle differences that some might feature.

Purging Your Regulator – Blow or Button?

If you remember your open water course, you have two ways to clear your regulator – blowing or hitting the button.

The exhaust valve is a one-way valve that you blow air through, or expels the bubbles while you breathe.

Some regulators have specially placed exhaust valves that are designed to keep the bubbles out of your way and sight – a pretty nifty feature if you don’t like getting tons of bubbles in your face just as you are trying to take a photo!

The purge button located right smack in the middle of your regulator body forces air from the tank through the second stage and out from the exhaust valve to clear any water.

All purge buttons should be relatively easy to operate, even with thick gloves and numb hands!

Regulator Mouthpiece

Do yourself a favor and get yourself a boil-and-bite mouthpiece that can be customized to fit your mouth.

Jaw fatigue after multiple dives a day is real, especially in colder water where you have a tendency to clench your jaws.

Having a comfortable mouthpieces can save you loads of energy, and even prevent blisters on your gums that an ill-fitting mouthpiece might cause.

Regulator mouthpiece

Venturi-Assisted Breathing and Diver Adjustment

Venturi-assisted breathing originated as a medical technique that uses a tube to deliver more oxygen to patients that struggle to breathe.

In the diving world, second stage regulators use the same science to improve airflow for less breathing effort.

Some second stages allow you to adjust the airflow manually, while others are set by a technician.

❓ 5. Frequently Asked Questions

What Is High Pressure?

High pressure is the pressure in your tank cylinder. The standard high pressure tanks hold 3000 psi / 200 bar, but some dive centers overfill them slightly and you might find your tank filled with 3300 / 210 bar.

What Is Intermediate Pressure?

Intermediate air pressure is what your first stage converts from the high pressure in your tank to the intermediate pressure in your hose or LPI, ready for further conversion into ambient pressure. This number is frequently around 150 psi, or 10 bar.

What Is Ambient Pressure?

Ambient pressure is what we breathe. On the surface, it is at 1 atmosphere (1 bar), and it steadily increases by 1 atmosphere/bar every 10 meters we descend. At 10 meters, it would be 2 bar, and at 20 meters, 3 bar, and so on.

💭 6. Final Thoughts On Scuba Diving Regulators

The scuba regulator is one of the most important pieces of scuba equipment you will own or use. You’ll need to regularly send it for servicing and keep it in tip-top shape. After all, it IS a crucial piece of your life support equipment!

Thanks for reading and happy bubbles!

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