Wow, there are so many regulators our there! How do you know which one to get? In order to make an educated decision you need to explore some of the vocabulary and options when discussing regulators.

When we breath underwater we can only tolerate a difference of about 0.14 atm/bar between the breathing air pressure and the pressure surrounding the lungs. This is why you can’t just breath from a hose going to the surface at 10 feet deep.

As we descend for our dive the pressure of the water on our bodies has to equal the pressure of the air that we are breathing. This is what an open circuit scuba regulator does.

Modern regulators are two-stage regulators. This means that the air in the cylinder is reduced to an intermediate pressure by the first stage and then it is reduced further by the second stage to match the ambient pressure for breathing (ambient means that surrounding pressure at whatever depth you are at). So, when you are purchasing a regulator you will need to buy not only a first stage, but also a second stage.

There a lots of things to consider, including:
1. Balanced or Unbalanced
2. Piston or Diaphragm
3. DIN vs Yoke
4. Number of Ports
5. Environmentally sealed or not

Balanced Vs Unbalanced Regulators

These terms refer to the valves used in the first stage of the regulator.

In an unbalanced valve the pressure from the cylinder presses on the valve and assists in opening it. However, as the pressure in the tank decreases this doesn’t assist with opening the valve. This means that there is minor variation in the performance of the regulator.
In a balanced valve high pressure air from the cylinder is routed around both sides of the valve opening. This cancels our, or balances the cylinder pressure causing no variation in the performance of the regulator.

This means that unbalanced regulators can be harder to breath from in deep or really cold environments. However, balanced regulators are not affected.

Bottom line: Balanced regulators are better.

Piston Vs Diaphragm Regulators

These terms are also about the first stage of a regulator. They are describing how the external pressure from the water (determining the ambient pressure). In a piston regulator the external water pressure acts on a piston (the main moving part of the first stage). In a diaphragm regulator the pressure acts on a diaphragm. For all intents and purposes there isn’t one that is better than another, but there are disadvantages and advantages for both.
Piston regulators have fewer moving parts and are therefor faster and cheaper to service. They have a slightly better performance at depth. They also often offer 5 low pressure ports.
Diaphragm regulators separate their interior parts from the water, reducing interior corossion and contaminant buildup. So they are better in cold environments and in water with particles like silt, sand and salt. Most diaphragm regulators only offer 4 low pressure ports.

Bottom line: There isn’t really that much difference between these two types of regulators.

DIN Vs Yoke/ A-Clamp

These terms describe the two different types of fittings for attaching the regulator to the tank.

DIN stands for Deutsches Institut für Normung and these types of regulators have fittings that screws directly into the tank. It’s more commonly used in Europe and for Tec diving (especially in caves and wrecks).

Mk17 DIN

MK 17 Yoke

A Yoke fitting screws over the tank. It’s also called A-clamp and is most popular in the UK and the USA.

Both types of fittings are reliable and used commonly. If you choose to go with a DIN fitting you can buy a DIN to yoke style converter which will give you the flexibility of using either one whichever is more convenient at the time.
All the scuba pro regulators that we sell can be converted to DIN, Chris has done this with his Tec diving set up.
At Octopus Diving our tanks are set up for Yoke (A Clamp) but we of course have DIN adapters.

High Pressure and Low Pressure Ports

The first stage of regulator has ports which connect other parts of the regulator like an octopus, inflator hose, pressure gauges, integrated computers (sometimes wireless) and any extras. These ports can be high pressure or low pressure ports.
Low pressure ports are used to connect only low pressure items, via a hose, to the first stage. This includes the second stage (that you are breath from and the Octopus), it also includes your buoyancy compensator inflator (also called your low pressure inflator).
The high pressure ports connect high pressure items such as your analog pressure gauge or air integrated dive computer.

Please note that high pressure and low pressure ports are different sizes to avoid mixing them up. In North America and Asia these are a standard size, but some European manufacturers use a different standard. This means that not all hoses will match with all first stages.

Bottom Line: It is useful to choose a regulator with multiple high pressure ports should you wish to add on any extras in the future.

Environmental Sealing

Some first stages offer environmental sealing. This means that water pressure doesn’t act directly on the piston or the diaphragm. This prevents mud, silt, salt and other contaminants from entering the first stage, reducing corrosion and contaminant build up. Also, this means that in extremely cold temperatures the mechanisms in the first stage are less likely to freeze and malfunction.

Bottom line: If you are diving in extremely cold to freezing water this is an important feature to look for in a regulator.

• MK 2