Deep-Six Underwater Systems, Inc.
"Add Depth to Your Life"

Table of Contents

1 Pressure and Gases
2 The Face Mask
3 The Snorkel
4 The Fins
5 Weight Systems
6 The Knife
7 The Wetsuit
8 Pressure and Water
9 The Ear and Pressure
10 The Sinus and Pressure
11 The Stomach/Intestine and Pressure
12 The Lung and Pressure
13 Barotrauma caused by External Air Spaces
14 The Buoyancy Compesation Device (BCD)
15 The Scuba Cylinder
16 The Scuba Cylinder Valve
17 The Regulator
18 Density and the Diver
19 The 4 Gas Laws
20 Hand Signals
21 Carbon Monoxide Poisoning
22 Hyperventilation
23 Nitrogen Narcosis
24 Diver's Flags
25 Sound Underwater
26 Color Underwater
27 Decompression Sickness
28 Breathing Oxygen
29 Deep Diving
30 Thermoclines
31 Thunderstorms
32 Underwater Life
33 Open Water Dives
34 The Final Examination
35 The Environment
36 Advanced Course

17 - The Regulator

     The high pressure in the scuba tank must be delivered to the diver at the same pressure as the surrounding water. The regulator does this. It makes little difference what brand is being used. They are all reliable, efficient, and have an extremely low failure rate. Law suits would abound if this were not true.

     In the modern single-hose regulator there are two stages. The first stage is that part that attaches to the tank. The primary second stage has the mouthpiece that goes in the diver's mouth. The air entering the first stage from the tank might be 3000 psi. The air leaving the first stage through the hose to the second stage will be about 140 psi. The air entering the diver's mouth from the mouthpiece will be at the ambient pressure. (Note: "ambient" means surrounding.)

     Once the regulator is attached to the tank, and the tank is turned on, there is no noticeable air flow. Air is not wasted when the diver isn't breathing in. When the diver inhales on the mouthpiece the pressure is lowered inside the second stage. Water on the outside pushes a diaphragm in. That is connected to a lever that opens the valve to the air in the hose coming from the first stage. As the 140 psi air pressure is lowered, another valve opens in the first stage and the air from the tank enters. When the diver exhales the process reverses and the air flow is shut off.

     Sometimes a regulator, that is not in a diver's mouth, is put in the water with the mouthpiece facing up. The water pushes the diaphragm in and the regulator starts to quickly release air by itself. To stop the air flow it is necessary to turn it over so the mouthpiece is pointing toward the bottom. After the flow stops the regulator may be released with no further "bleeding."

     Although there should be no leaks with most regulators, a minor leak is not something that should cause grave concern. (Some regulators are designed to leak small amounts of air in order to keep water from entering the regulator's interior.) A leak that is a barely audible hiss, although it should be repaired, will not subtract much from the dive time. To illustrate this: If you let the air that is leaking flow into a water-filled cubic foot box, so that as the air went in water would come out, the time it took to fill the box would roughly amount to about 1 minute of dive time.

     Breathing underwater is about the same as breathing in the atmosphere. The inhale should be slightly deeper, followed by the exhale. There should be no pause between the two. It is important to keep the lungs well ventilated without risking lung injury by holding the breath and ascending.

     If the regulator is put in the mouth underwater it will be necessary to blow the water out of it prior to breathing in. A simple exhale will accomplish that. A regulator should never be placed in the mouth upside down. When that happens the exhaust port is above the mouthpiece making it impossible to get the water out of the interior. The inhale will contain mostly water resulting in a possible drowning! This is especially important to remember when a regulator is handed to a buddy!

     On the rare occasion some water may leak into the second stage. There are three main reasons for this. 1. The mouthpiece may have a hole or tear in it; 2. The exhaust port valve is not lying flat against the housing; and 3. The diver is not making a good seal with the mouth. There are rare instances where a leak is the result of a unseated diaphragm or cracked housing. Having a regulator serviced at least once per year should prevent all of the above except for the mouth seal.

     Throwing up underwater is rare. That is fortunate. Thinking about the process leads one to many questions. Should you throw up into the regulator? Should you take the regulator out and risk drowning on the inhalation? Will the diver remain under control during the process? Don't dive if there is a feeling of nausea. If the diver feels they are about to throw up try to move safety to the surface. If it has to be done under water, I think the best procedure would be to throw up into the regulator, replace the regulator with the alternate air and resume breathing. Clean out the primary second stage by shaking and pressing the purge button, and then return that to the mouth. Be aware: This author has never put this to the test nor is aware of anyone else successfully doing it!

     The proper procedure to remove a regulator from the tank is:

  1. Shut off the air from the tank.

  2. Purge the air from the regulator by pushing the secondary purge button. This will prevent the loud and damaging pop to the tank's O ring, and will make removal of the regulator easier.

  3. Remove the hoses from the BCD.

  4. Carefully remove the regulator from the tank - before doing this be sure the pressure has been removed!

  5. Turn the tank on slowly so a stream of air is flowing and then hold the dust cover (yolk cap) in it. This will dry the water from the dust cover. Prevent the spraying water from entering the sintered filter.

  6. Place the dust cover on the opening to the regulator and turn the tank knob to hold it in place.

  7. If the regulator has been used in salt or contaminated water it should be rinsed with fresh water. During the rinse the purge buttons must not be depressed or water may get into the regulator's interior.

  8. Afetr rinsing, if there is a method to keep the the purge button(s) depressed it should be done to keep pressure off the low-pressure seat(s).

  9. Hang the regulator up to dry.

     There are high and low-pressure ports on the first stage of the regulator. The high-pressure ports are usually stamped, "HP." The high-pressure port threads are larger than the low-pressure port threads. That has not always been the case. Many years ago regulators had the same threads on both ports and some divers accidentally put a low-pressure hose on a high-pressure port. When the pressure in the hose exceeded 400 psi it would explode! The spg is put on the high-pressure port. The BCD hose, the alternate air hose, the dry suit hose, and the secondary regulator hose are all attached to low-pressure ports.

     How often should a regulator be overhauled? It really depends on how it is used. If it is frequently used in salt water the service should be done at least once per year. A less heavily used regulator in fresh water might require servicing after two years. If the period is much longer certain parts of the regulator may permanently seal due to corrosion. Servicing involves the complete disassembly and cleaning of the regulator, lubrication of the O rings, replacement of worn parts, and function testing. An unserviced regulator may begin to destroy itself due to moving parts scoring other parts! 

Copyright Information about this text, DIVING WITH DEEP-SIX is as follows: Copyright 1996 - 2007 by George D. Campbell, III; President. All Rights Reserved. This file may be posted on Electronic Bulletin Boards for download, but may not be modified, printed for distribution, or used for any commercial purpose without the author's written permission. is using this material with the permission of Deep Six. The full version is available at:
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