Regulator - key components
Regulator set A regulator is a summary term of a unit that actually consists of several different components:
  • 1st Stage (Top right)
  • 2nd Stage (also referred to as a Demand Valve) (Bottom left)
  • Octopus (also a 2nd Stage) (Bright yellow)
  • A pressure gauge (often referred to as an SPG - submersible pressure gauge) (Bottom right)
  • Hoses connecting the various units
First Stage Regulator

Piston or Diaphragm Regulator

There are two types of first stage regulators - Piston or Diaphragm, with additional sub-categories such as the unbalanced and balanced regulator. If you are interested how they work in detail, there are some good entries in Wikipedia and Youtube

But for this section we try to keep this simple. A piston regulator is simpler in design and can have a high flow rate, making them easy to breath. A diaphragm regulator is more complex and is "lower" performing (i.e. gas flow), but it is easy "environmentally" sealed, therefore allowing diving in cold water.

If you want to dive in the UK and water temperature of 12°C or below (cold water diving), you will need to have an environmentally sealed 1st stage. However, both design nowadays are available for cold water. In terms of cost, you will find the cheap and really expensive regulators usually to be Piston Regulators and the mid-ranged regulators to be Diaphragm Regulators.

The key difference between an unbalanced and balanced regulator is as the pressure increases through depth and the cylinder pressure decreases, a balanced regulator will keep the flow rate constant, while an unbalanced will not. The unbalanced regulator will be harder to breath from. And just to confuse a bit, you will also hear of "overbalanced" regulators, here the pressure is higher than what you actually need, meaning it can be a very easy breath - there is an increased risk of "freeflows" with such a regulator - regulators of this type will have an adjustment knob or similar on the 2nd stage (allowing you to adjust it while diving).

A-Clamp (Yoke) or K-Valve (DIN)

Regulator with A-ClampRegulator with DIN Fitting

This is a much more interesting question. DIN valves (right photo) are rated to 200 bar (5 threads deep) or 300 bar (7 threads deep), while an A-Clamp regulator will be rated to 232 bar (left photo). However, choosing one doesn't exclude the other. To use an A-Clamp on a DIN cylinder, you just need to screw in an adaptor. For a DIN regulator to be used on a A-Clamp cylinder you can buy an adapter where the DIN regulator gets screwed into. In general, the A-Clamp is popular in the UK, with Europe following the DIN model - however the DIN model has become more popular in recent years, especially with the technical diving community.

Note: You can still put a 300 bar DIN into a 200 bar cylinder, but not a 200 bar DIN stage into a 300 bar cylinder, as it won't reach the end to make a seal.

Ports and Pivot Head

Ports are where you screw in all the hoses to all the other pieces of equipment. Your pressure gauge, 2nd stage and Octopus. The pressure gauge will be plugged into the High Pressure port, while the others into the low pressure ports. The minimum you need is 1 High Pressure (HP) port and 2 low pressure ports. However, if you want to use if to inflate your dry-suit, you will need at least 1 additional low pressure port. If you have a two bladder design (for your BCD wing), you will need another port for that as well. Or even attach a pressure transmitter (another HP port required) - it is recommended to always keep your SPG (submersible pressure gauge) as a back-up, in case the electronics fail. 

A sub-feature is that some 1st stages head can be pivoted allowing easier routing of any hoses. This is quite useful if you have some tight fitting equipment. However, this means there is another area where the 1st stage can leak and it does require additional servicing. 

For practical reasons and available choice, we recommend you look for a 1st stage that has at least 3 low pressure ports (4 preferred) and 2 high pressure ports, this gives most divers sufficient flexibility.

Second Stage Regulator

Second Stage Regulators reduce the pressure delivered from the first stage (also called the intermediate pressure - ca. 10bar) to the surrounding pressure (ambient pressure) around you, allowing you to breath comfortable underwater. You will find, similar to the first stage, different options depending on your type of diving.

Balanced and Unbalanced

You will balanced and unbalanced second stages on offer. The concept is very simple, a balanced second stage, will adjust its performance and will give you a consistent breathing resistance regardless of depth, while an unbalanced one cannot do this. An unbalanced regulator will either have a "too easy" breath at surface or a "harder breath" at depth. However, this is not as critical as it sounds, many regulators have the ability to make adjustments as depth increases and if you are a recreational diver, who will not venture often beyond the 30 metre mark it is only of limited consequence.

Inhalation Adjustment and Venturi Control Options

You will find a second stages fitted out with little adjustment buttons, you effectively can adjust the breathing resistance whilst diving. There are in principle two types of adjusters. The Venturi Switch (usually a lever)  marked with "+" and "-" (pre-dive) symbols. This effectively increases the valve pressure inside your second stage, increasing the effort to open the valve - this decreases the risk of free flow - when needed you can still breath from it and pull the lever to make it easier to breath. The second alternative is the "Inhalation Adjustment", often a little knob (often embedded around the Venturi control lever), allowing you to adjust the breathing resistance while diving (this is typically seen on balanced second stages). If you intend to do a lot of mixed diving (esp. cold water diving) - this is a worthwhile feature to have.

Regulator with BCD inflator

Alternative Air Source - Redundant Second Stage - Octopus

You will find on your regulator set usually a brightly coloured second stage (bright yellow is typical). This can be used by yourself, if your primary second stage fails, or your buddy requires an "alternative air source". The brightness allows for easy recognition by yourself or your buddy. It is recommended you have at least the same performing regulator on it, because in an emergency you are likely to require a better performance as you or the victim will be breathing harder. 

You will find some divers will only have one seconds stage regulator and their second "alternative air source" (AAS) will be attached to their BCD inflator (see photo on the right). This option reduces the weight of your kit (especially for travelling), but has the drawback that the Inflator hose is quite short, which requires you to first remove your primary regulator and give it to your buddy. You then will need to use your BCD AAS to breath and control your buoyancy - which means it does require a bit of practice as you are much more movement restricted.

Nitrox / Mixed Gas

Most regulators are able to take Nitrox (Enriched Air) up to 40% O2 without any modifications. However, do check the owners manual to be sure. Most regulators will require special O2 cleaning and the use of O2 grease, before a richer gas over 40% O2 can be used. Especially lightweight regulators which use special materials (such as Titanium) are often not capable of using enriched gases of higher percentages. This is one reason why technical divers tend to have quite chunky equipment for their diving.

Lightweight Regulators

In recent years, manufacturers have been experimenting with use of advanced lightweight materials - Titanium, ceramics, special alloys to name a few. These are often regulators designed for travelling, especially attractive with the ever decreasing weight allowances from airlines. If you intend to dive in the UK, you must check their ability to be used in waters below 10°C, as many lightweight regulators are not cold water rated. However, some of the very expensive lightweight regulators (often using carbon technology) have been able to meet the strict requirements for cold water diving.
Hoses and SPG


There are a number of different hose types out there. To keep it simply, you fill find two basic types - High Pressure and Low Pressure hoses. High Pressure hoses are linked between the 1st Stage and the Submersible Pressure Gauge (SPG). Low pressure hoses connect between the 1st stage and the regulators, BCD and dry suit. There are a number of different designs and materials available - ranging in colour and flexibility. We have changed all our hoses to flex hoses, making the hoses easier to route around your kit and manage. Once you start diving, you might find certain hoses are too long or too short for your set-up, most dive shops offer a hose customisation service, which allows you to get the hose length appropriate for your kit.

Submersible Pressure Gauge (SPG)

The SPG or Submersible Pressure Gauge allows you to read the residual pressure in your cylinder. There are many options from basic simple button sized, to large complex fully integrated computer gauges such as the Suunto Cobra2. You should ensure your pressure gauge is easy enough for you too read and uses the right type of units (bars or PSI), which ever your are more comfortable with. Often the SPG is integrated in a larger console and may include compass, depth gauge and other instruments - this is quite practical, as a lot of small kit is in one place and attached to you as diver (which means you know where it is and you are unlikely to loose it).