How a Diving Regulator Works

A scuba diving regulator is no ordinary piece of equipment. For divers, regulators are the lifeline that connects them to the precious air inside their tank. And since they’re often going deep below water for long periods of time, you better bet that divers will be interested in regulators! While you might think regulators have a simple action to perform, what’s going on behind-the-scenes is actually pretty complex. The moment you inhale through the mouthpiece you set off a tonne of activity inside. Let’s look at how a diving regulator works and discover the sheer genius of diving science!

What is a diving regulator

Maybe all you know about diving regulators is that they’re a piece of equipment, and your knowledge stops there. If so, listen carefully, because diving regulators are no funny business. They are literally the most important piece of equipment you could carry with you while underwater – forget about your mask and wetsuit, a diving regulator is what will keep you alive. Essentially, diving regulators are the medium between you and your air tank when underwater. The diving regulator converts the high-pressure air from your gas cylinder into breathable air that you can use. Without the diving regulator, the high-pressure air from the gas cylinder could seriously injure your lungs. Together, the two pieces of equipment make a self-contained underwater breathing apparatus… that’s right, you guessed it, SCUBA.

Before we begin: Know your lingo

Diving regulators are important pieces of equipment, but the way they work is fairly simple and easy to understand. That said, there’s a lot of lingo that’ll make things confusing if you’re unsure about diving terminology. So before we begin, here are a few new words to add to your diving dictionary:


This term refers to the part of the diving regulator that attaches to your tank valve and converts high-pressure tank oxygen to intermediate pressure air, This refers to the part of the diving regulator that you put into your mouth, which converts the intermediate pressure air into breathable ambient air, Fairly simple, but this refers to the air pressure inside your gas cylinder. When you’re diving, air is compressed to extremely high pressures so that you can carry as much oxygen with you as possible. Here’s a frame of reference: pressurised tools used by mechanics operate at 90 – 140 psi. When full, a scuba tank is pressurised to 3,000 psi. That’s a lot of pressure! This is the pressure of the air that’s sent from the first stage to the second stage. Generally, the pressure would be around 125 – 150 psi above ambient. This is the pressure that is surrounding you when underwater. Ambient pressure increases with depth, so the deeper you go, the higher the pressure. Diving regulators will convert the high-pressure air inside your cylinder and deliver it to your lungs at ambient pressure. Since you’ll be ascending and descending while diving, regulators have to constantly adjust to make sure your air is delivered at ambient pressure.

How diving regulators work

So, now you know that there are two stages, or pieces of equipment, involved with diving regulators. The first stage is taking the high-pressure tank oxygen and reducing it to intermediate pressure, and the second stage reduces the immediate pressure air to ambient pressure. Let’s look at each of these stages more closely.

How a first stage diving regulator works

The first stage regulator attaches to your tank valve and lowers the 3,000 psi tank pressure to an intermediate pressure of about 140 psi, releasing that through a valve that leads to the second stage regulator.

First stage diving regulator parts:

There are two different types of first stage regulators, piston and diaphragm types. Both have either a DIN or yoke-style fitting that connects them to your tank, an inlet filter to prevent contaminants from entering the regulator, two chambers, a bias spring, intermediate-pressure fittings for second stage, inflator assemblies & accessories, and high-pressure fittings for gauges and transmitters. Not sure whether you should go for a piston or a diaphragm? There’s not much difference between the two, however a piston regulator can provide a lot more air under high pressure than a diaphragm regulator. Here’s a quick breakdown between the two:

Difference between piston & diaphragm regulators

These regulators have good airflow and only one moving part. That said, they do tend to be pricier than diaphragm regulators as they require a precise machining process. On the other hand, less moving parts makes them more reliable and cheaper to maintain. There are many parts to a diaphragm first stage which can be annoying for some people, but they are easier to manufacture and therefore cheaper to purchase. For more experienced divers, you might notice lower performance compared to a piston regulator. For those who are out diving for a good time every now and then, you won’t notice a thing.

Here’s how first stage regulators work in more detail:

1.A first stage regulator has two air chambers which are separated by a valve. The valve remains open when the regulator is not pressurised, 2.When you connect the first stage regulator to a tank, the high-pressure oxygen from the tank will flow into the first chamber, through the valve, and into the second chamber. The valve connecting the two chambers will remain open until the air in the second chamber is regulated to intermediate pressure, 3.When the oxygen in the second chamber is reduced to intermediate pressure, the valve connecting the two chambers will close. This will stop high-pressure air from the tank flowing into the second chamber and injuring the diver, 4.As you inhale, air from the second chamber will be released to the second stage regulator, 5.When the second chamber releases the oxygen, its pressure will drop, allowing the valve connecting the two chambers to re-open. Air will flow from the first chamber into the second chamber once again, until the second chamber pressure rises to intermediate again, 6.When the second chamber air reaches intermediate pressure, the valve between the two chambers will again be forced to close.

How a second stage diving regulator works

The second stage diving regulator, which connects to your mouth, is designed to reduce the air pressure from intermediate to ambient. It is also important for a second stage regulator to allow air to flow into your mouth only when you inhale – imagine all the unstoppable oxygen coming in otherwise! Not only would that deplete your tank, but it wouldn’t feel very comfortable.

Second stage diving regulator parts:

– We hope you know what this is… the piece… that goes in your mouth, – A one-way valve that lets air leak into the water when you exhale and keeps water from entering, – When pushed, this button forces air to continuously flow into the second stage chamber and expel any water in the mouthpiece. 

Here’s how a second stage diving regulator works in more detail:

1.While the first stage regulator had two chambers, the second stage has only one air chamber with a valve that connects to the hose from the first stage, 2.This valve remains closed until you inhale, separating the intermediate pressure in the hose from the ambient air in the second stage, 3.Second stage regulators are fitted with flexible silicone diaphragms that keep water out and air in. A lever resting on the diaphragm operates the valve that connects to the first stage hose, 4.When you inhale, air pressure is lowered in the chamber as you have taken some of that oxygen into your lungs. With less air pressure, water from outside gently pushes on the diaphragm, which then pushes on the lever, opening the valve and letting air from the first stage rush into the chamber until it reaches ambient pressure, 5.Since it is the surrounding water which pushes on the diaphragm and allows oxygen to be adjusted, then the second stage regulator automatically adjusts to the ambient pressure on its own. Thought a diving regulator was just a simple hose connected to a tank? We’re amazed by the sheer genius of the design of these two regulators. Some incredible people have created these pieces of equipment, just so people like us can get out there and explore what’s underwater! Aren’t we lucky?


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