I am attempting to write my blog updates in the order in which I purchased equipment for myself.  Therefore, the next thing I will talk about is the regulator.  Regulators are designed to deliver breathing gas to the diver from a compressed gas cylinder.  Now, I use the term “breathing gas” because this can be any gas in a range of different mixes.  I currently only use compressed air or enriched air (or Nitrox) so I will limit my discussion to regulators that will deliver those breathing gases.  Also, I will be limiting my discussion to modern two-stage regulators.  If you are interested in vintage equipment and would like more information about those, be sure to check out Derek Wheeler’s vintage equipment and history blog.

There are a plethora of designs on the market today from many manufacturers, and since Nitrox is fairly common place, most (if not all) deliver enriched air up to 40% oxygen without modification.  The most common design today is a two-stage open circuit regulator.  The first stage connects to the compressed gas cylinder and reduces the pressure that is delivered from the cylinder to an intermediate pressure.  This is usually in the range of about 150 psi (10 bar) or less.  The gas then travels to the second stage regulator.  This delivers the gas on-demand.  By that I mean that the gas is only delivered when the diver takes a breath.

There are different designs of first stage regulators.  There are balanced and unbalanced first stages.  A balanced first stage delivers gas with a constant pressure.  That means the first breath from a compressed cylinder will take the same effort as the last and will not generally be affected by depth.  An unbalanced first stage uses the cylinder pressure to push the first stage valve closed.  Therefore, the pressure through the first stage is directly affected by the cylinder pressure.

Photo courtesy Ellie Haveman

First stages are also available in a piston-type and a diaphragm-type.  Without going into the actual design of each type, I will say that piston-type regulators are less complicated and easier to manufacture.  Therefore they are generally cheaper than diaphragm-type regulators.  However, they are exposed to water and any contaminants in the water.  A diaphragm-type first stage is a bit more complicated.  However, it can be sealed from the elements and is a much better choice for divers that dive in cold water or contaminated conditions.

Another option when selecting a first stage is how it will connect to the cylinder.  The most popular option among recreational divers is a yoke connection.  A yoke connection clamps an open hole on the regulator against an open hole on the cylinder. The diver screws the clamp in place finger-tight, and once the cylinder valve is opened, gas pressure completes the seal along with an o-ring.  Another connection type is a DIN connection.  A DIN connection is a direct screw in connection to the cylinder.  This type of connection is considered more secure and is favored by technical divers.  However, it is far less common among rental operations and recreational charters.

The second stage regulator is available with a few “options”.  First of all, they may be available with user adjustable pressure sensitivity.  This means you can adjust how hard you have to breath in to get the gas to be delivered.  This is referred to as the “cracking pressure”.   Also, they may have a venturi control switch.  This allows the user to switch between dive and surface modes.  In dive mode, the flow of air will be delivered smoother and easier while underwater and the surface mode will prevent free-flows on the surface since there isn’t any water pressure holding the valve closed.

Now, I know the information I have just covered is very technical.  But the question you need to ask yourself is what type of diving you will be doing.  If you plan to dive warm waters, an unsealed piston-type regulator would be just fine, and would be cheaper than a diaphragm-type sealed regulator.  I dive cold water so I opted for a balanced diaphragm-type environmentally sealed first stage regulator.   I also have a yoke connection since that is the most widely used connection type and I planned on doing some travel diving.  However, I have investigated switching to DIN if I ever decide to go technical.  A member of the Talking Scuba staff, Jeff Fossmo, switched his connections to DIN for his technical training.  If you see yourself going for technical training, this is one of the things you will want to investigate.

You don’t want to forget to add a SPG (submersible pressure gauge) to your regulator set-up.  These connect to the first stage via a high pressure port.  This can be a simple “button” analog gauge or an analog gauge connected by a high pressure hose.  I would not suggest using too small of a gauge for your primary gauge as they can be hard to see underwater.  The pressure gauge can also be integrated into your dive computer, but this is a topic for another blog entry.

If you have any questions about this topic or any of my other blogs please send me an e-mail at jeff@talking-scuba.com.  Safe diving!