Regulators, Regs, 1st stage, 2nd Stage, Octopus, Demand Valve, Alternate Air Source are all names you should be familiar with.
The Regulators Explained
Regulators enable you to use the air in your scuba cylinder, they regulate air flow between your cylinder, 2nd stage/octopus and all other hoses and attachments that require air, such as your pressure gauge, dive computer, BCD inflate, etc. A regulator is needed to reduce the very high air pressure in the tank to the ambient pressure of the water surrounding you. It does that in two steps. Regulators are also called demand valves because they provide air by opening when the diver demands it by breathing in, and closing when they breathe out. Regulators actually consist of two stages. The first stage and the second stage or demand valve as shown in the diagram. We will now take the components and explain their function a little more:
The first stage
The function of the first stage is to reduce the pressure in the air tank, usually around 200 bar, to an intermediate pressure, usually about 9.5 to 10.5 bar. All first stages therefore have two chambers, one that is at the same high pressure as the tank, and the other with intermediate pressure. The first stage can have a varying number of ports, some of them are high pressure (often labeled HP) ports that connect to the pressure gauge or dive computer. Those ports require special high pressure hoses and have a different, larger connecting thread than the low pressure ports (often labeled LP). LP ports connect to low pressure items: the second stage, an alternate breathing source (octopus), and a hose for inflating the BC or dry suit. The more ports, the more hoses can be connected, and the easier it is to connect at the right angle.
First stages can be made from chrome-plated brass or titanium, there are two different designs, one uses a piston and the other a diaphragm. Piston first stages are usually less expensive and are easy to service, but not so easy to adjust should the need arise. Piston designs have few moving parts, are very reliable and can reach very high air delivery rates. Diaphragm designs, unlike pistons, are totally sealed and do not allow water or debris to enter the stage, they are more expensive, but are easier for service personnel to adjust.
The first stage can also be balanced or unbalanced. Balanced refers to a design that delivers the same amount of air regardless of the pressure in the tank or how hard the diver breathes. In unbalanced designs, there is less air as the cylinder pressure falls, making it progressively harder to breathe, though some of the newer unbalanced designs are much improved. First stages also differ in the type of valve they connect to either A-clamp (also known as a 'yoke' or 'International fitting or has a DIN fitting to connect to the pillar valve on the top of the cylinder.. The first stage shown above and in the header is of the 'A' Clamp design.
The second stage
The primary task of the second stage is to reduce the intermediate air pressure in the hose coming from the first stage down to the exact same pressure as the surrounding water so that breathing is as easy as possible. Second stages can be made of Chrome plated brass, plastic or a combination of both. The mouthpiece can be made of plastic, neoprene and silicone. Second stages include the mouthpiece, an exhaust valve and a purge valve that's used to test and clear the regulator. The purge valve is activated with a purge button normally located on the front of the second stage.
Most modern second stages have a "downstream" inlet valve. This means the valve opens away from the air pressure. If it were to fail, it remains open and continues to deliver air. An "upstream" valve would close, cut off air, and perhaps lead to dangerous overinflation in other parts of the system. You wouldn't want to find yourself without air to breathe and a BC getting overinflated. Regulator manufacturers offer a large variety of second stages of different design and with different features, each manufacturer has their own patented technologies and materials. There may be antifreeze kits, special orthodontic mouthpieces, vacuum assist for easier breathing, inhalation effort adjustment, dry valve systems to keep water out completely, special balanced valves to minimize the effort to overcome valve resistance etc.
The first stage
The function of the first stage is to reduce the pressure in the air tank, usually around 200 bar, to an intermediate pressure, usually about 9.5 to 10.5 bar. All first stages therefore have two chambers, one that is at the same high pressure as the tank, and the other with intermediate pressure. The first stage can have a varying number of ports, some of them are high pressure (often labeled HP) ports that connect to the pressure gauge or dive computer. Those ports require special high pressure hoses and have a different, larger connecting thread than the low pressure ports (often labeled LP). LP ports connect to low pressure items: the second stage, an alternate breathing source (octopus), and a hose for inflating the BC or dry suit. The more ports, the more hoses can be connected, and the easier it is to connect at the right angle.
First stages can be made from chrome-plated brass or titanium, there are two different designs, one uses a piston and the other a diaphragm. Piston first stages are usually less expensive and are easy to service, but not so easy to adjust should the need arise. Piston designs have few moving parts, are very reliable and can reach very high air delivery rates. Diaphragm designs, unlike pistons, are totally sealed and do not allow water or debris to enter the stage, they are more expensive, but are easier for service personnel to adjust.
The first stage can also be balanced or unbalanced. Balanced refers to a design that delivers the same amount of air regardless of the pressure in the tank or how hard the diver breathes. In unbalanced designs, there is less air as the cylinder pressure falls, making it progressively harder to breathe, though some of the newer unbalanced designs are much improved. First stages also differ in the type of valve they connect to either A-clamp (also known as a 'yoke' or 'International fitting or has a DIN fitting to connect to the pillar valve on the top of the cylinder.. The first stage shown above and in the header is of the 'A' Clamp design.
The second stage
The primary task of the second stage is to reduce the intermediate air pressure in the hose coming from the first stage down to the exact same pressure as the surrounding water so that breathing is as easy as possible. Second stages can be made of Chrome plated brass, plastic or a combination of both. The mouthpiece can be made of plastic, neoprene and silicone. Second stages include the mouthpiece, an exhaust valve and a purge valve that's used to test and clear the regulator. The purge valve is activated with a purge button normally located on the front of the second stage.
Most modern second stages have a "downstream" inlet valve. This means the valve opens away from the air pressure. If it were to fail, it remains open and continues to deliver air. An "upstream" valve would close, cut off air, and perhaps lead to dangerous overinflation in other parts of the system. You wouldn't want to find yourself without air to breathe and a BC getting overinflated. Regulator manufacturers offer a large variety of second stages of different design and with different features, each manufacturer has their own patented technologies and materials. There may be antifreeze kits, special orthodontic mouthpieces, vacuum assist for easier breathing, inhalation effort adjustment, dry valve systems to keep water out completely, special balanced valves to minimize the effort to overcome valve resistance etc.
So now you know what you are talking about, let's go buy your new Regs
How to Choose
Selecting the right regulator requires quite a bit of research and definitely the advice of an experienced diver, diving instructor or expert. The various technologies and features not only have an impact on price, but they also make a regulator more suitable for certain kinds of diving, this can be essential for technical and advanced diving. Novice divers should primarily be concerned with the ease of breathing provided by a regulator, you do not want to feel like you are trying to suck a golf ball through a garden hose with every breath you take. One problem is regulators are difficult to test in the store at 1 atm, so research is the key. I also recommend that you pay attention to the mouthpiece one that does not fit correctly or has sharp edges can hurt your gums or make it difficult to keep water out. Some may be, or feel too heavy, as a result, you may bite too hard on the mouthpiece or get tired from fighting to keep the regulator in place. One tip here is to take with you a few steri wipes or alcohol cleaning wipes as you never know what the previous customer may have had when they tried the mouth piece.
The First stage should have no less than one HP port for your cylinder contents gauge and three LP ports for your second stage, octopus/alternate air source and BCD inflate. If you think that someday you may take up drysuit diving, make sure there is a spare port for the drysuit hose also.
Above all, the key is research, check the internet, read reviews, ask friends, dive clubs, instructors before you choose.
Selecting the right regulator requires quite a bit of research and definitely the advice of an experienced diver, diving instructor or expert. The various technologies and features not only have an impact on price, but they also make a regulator more suitable for certain kinds of diving, this can be essential for technical and advanced diving. Novice divers should primarily be concerned with the ease of breathing provided by a regulator, you do not want to feel like you are trying to suck a golf ball through a garden hose with every breath you take. One problem is regulators are difficult to test in the store at 1 atm, so research is the key. I also recommend that you pay attention to the mouthpiece one that does not fit correctly or has sharp edges can hurt your gums or make it difficult to keep water out. Some may be, or feel too heavy, as a result, you may bite too hard on the mouthpiece or get tired from fighting to keep the regulator in place. One tip here is to take with you a few steri wipes or alcohol cleaning wipes as you never know what the previous customer may have had when they tried the mouth piece.
The First stage should have no less than one HP port for your cylinder contents gauge and three LP ports for your second stage, octopus/alternate air source and BCD inflate. If you think that someday you may take up drysuit diving, make sure there is a spare port for the drysuit hose also.
Above all, the key is research, check the internet, read reviews, ask friends, dive clubs, instructors before you choose.
