How to choose the best regulator

Choosing a Scuba Diving Regulator can be one of the biggest and toughest decisions you make when purchasing your dive kit. There is a lot of different aspects, components and technologies to consider, let alone the cost involved. To help to prepare you for the final decision we'll run through some of the key features and technologies of a regulator set so that you can make an informed decision.

When shopping for a regulator it is always recommended to choose a primary and octopus from the same brand. The pressures at work within each manufacturer's regulators can differ slightly so mismatched products may not work as intended. There is also only so many ways you can design and build a regulator so the basic types and concepts apply to all manufacturers but with their own spin and clever names for how they do it.

A regulator has four main components:

First Stage

The first stage does a lot of the work, converting your cylinder pressure from up to 300 bar down to usually somewhere between 9 and 10 bar, ready for your second stage to use it on demand. As with everything in this world you get what you pay for, with a more expensive first stage being able to deliver higher flow rates, respond faster to pressure drops and incorporate more features.

There are four main variations of a first stage design which are made up of the mechanism design (piston or diaphragm) and whether it is unbalanced or balanced.

Design
Piston and Diaphragm are simply two ways of doing the same basic thing but they do tend to lead in certain directions. Piston first stages are often fitted to seriously high-performance regulators with unbelievable flow rates, etc whereas diaphragm first stages, whilst still high performing, are more commonly found in cold and extreme cold water regulators because they are easier to protect.

Balancing
Un-balanced first stages are the simplest and are therefore cheaper but their performance is affected by the cylinder pressure as it drops and ambient pressure as you dive deeper. Balanced systems offer consistent performance by compensating for these two factors but this makes them more complicated and a little more expensive as result.

Fitting
Pretty much every regulator comes with the choice of either a DIN or A-Clamp / Yoke fitting for connecting to your cylinder. The choice is purely personal but DIN is a safer fitting as it traps the sealing o-ring whilst A-Clamp / Yoke merely pushes against it which can mean it can be forced out under pressure. Choosing DIN has another advantage in that it can be temporarily converted to A-Clamp / Yoke using an inexpensive adaptor which means you can have the best of both worlds.

Extras
Everything beyond these basic elements is purely extra but in the same way a basic spec car is essentially the same as the top of the line version feels better to drive, it definitely feels nicer to dive with a high spec regulator.

Some extras you are likely to come across are:

Environmental Seal - Totally seals off the internal components from the outside water, protecting them from contamination and the cold. More likely to be found on a diaphragm first stage but there are piston first stages available with it. It's a must if you plan on diving in water temperatures below 10 degrees Celsius to reduce your risk of a freeflow.
Heat Exchanger Fins - These fins increase the surface area of the first stage to help dissipate the cold that is generated as the air in the cylinder decompresses, helping to reduce the risk of a free flow under extreme use.
Swivelling Turrets - Low pressure swivelling turrets allow for a bit of extra freedom and movement.
Coatings - Most first stages are made from marine brass which is then chrome plated to provide a bit of extra protection. Tougher and more durable coatings such as Physical Vapor Deposition (PVD) can be found on higher spec regulators.

Second Stage

The second stage has the job of bringing the intermediate pressure down to a pressure that you can breathe as and when you need it. You are likely to only come across two variations in how this is achieved, using either a downstream unbalanced or balanced valve. Upstream valves are very few and far between because they don't offer an important safety feature that downstream valves provide... If they freeflow a downstream valve will be forced open with the increased flow whereas an upstream valve is effectively forced shut in this situation (ie. not providing air!).

With regards to the unbalanced and balanced side of things, the same principles apply in that performance is consistent throughout the dive with a balanced second stage.

Extras
As with the first stage, a higher specification second stage with more features is nicer to dive with than a basic model but it will do the same job. Here are some of the extras you are likely to come across:

Diver Adjustable Inhalation / Cracking Resistance - This allows the diver to adjust the inhalation effort required to open the valve and let air flow through. This is purely the first bit of effort as more second stages are designed to assist with the airflow for a more responsive breathe. Bear in mind that the factory default is the optimal setting and you can only increase the effort required to open the valve.
Venturi - This has a lot of different terms and implementations but the basic principle is that an area of low pressure is created behind the second stage diaphragm to help pull it inwards, pushing the valve lever down and opening the valve wider. Some regulators have an adjuster, some are automatic and some are pre-configured.
Heat Exchangers - Some cold water approved second stages have finned sleeves over the hose inlet to help dissipate the cold in the same way as mentioned for the first stage.
Metal Components - Some second stages use metal valve barrels and/or housings to improve cold-water performance as the metal has a higher thermal transfer characteristic than plastic. As a further upgrade, Carbon-based regulators are both lighter plastic and better at transferring heat than metal.
Coatings - High specification models may feature PVD coated elements to improve their aesthetics and increase the resistance against scratches and scuffs.

Octopus (Alternate Air Source / Alternate Second Stage)

An Octopus is simply a modified version of a standard second stage that has been fitted with a longer hose to make it easier to donate it to your buddy in an out of air situation and also with high visibility yellow panels to make it more obvious.

When it comes to buying an octopus the temptation is to opt for the cheapest one you can get but think about when it is likely to be used in earnest. A diver that you are donating it to in an out-of-air situation is not necessarily going to be as absolutely calm as they could be and is likely to be breathing at a harder and higher rate than normal until the situation has calmed down a bit. Do your buddy a favour and choose an octopus that has a reasonable performance level and flow rate, they certainly appreciate it when sucking on it to get their breathe back.

Hoses

Not all regulator hoses are created equal! There are three regulator hose types:

Basic rubber hose - These are stiff, heavy and prone to deterioration when exposed to UV, etc.
Rubber hoses with a larger internal diameter - referred to as superflow or something similar, have the same basic construction and problems with rubber hoses but the larger internal diameter offers better performance and flow rates
Braided hoses - These are lighter, have a higher burst pressure (improved safety) are much more flexible and are more resistant to UV and contamination damage. More and more manufacturers fit braided hoses as standard now.

Nitrox / Enriched Air

If you plan on diving with nitrox / enriched air gas mixes you are going to need to take note of the out of the box oxygen compatibility percentage. Most regulators are compatible with an oxygen content of up 40% which will be more than sufficient for most divers.

Beyond that point, you'll need to look for a dedicated Nitrox Regulator that is compatible with oxygen percentages of up to 100%.