Apeks XTX Regulators

It is difficult to give you a meaningful answer regarding breathing performance of ANY of the primary regulators we sell, including our own DGX Gears brand, in relation to other specific brands or models we don't sell. However, perhaps we can put the performance issue in perspective: In reality, any modern balanced general purpose scuba regulator, designed to perform to EN 250 standards and properly maintained, is capable of delivering gas more than adequate for the needs of two sport divers (primary plus an octo). That's not to say there aren't poorly performing sport regulators in the market, but you can't buy them at Dive Gear Express.

There is no perfect regulator; they all have strengths and weaknesses that make each uniquely more or less suited to your needs. Keep in mind that a big brand name and high price are factors that rarely equate to better performance or better value. When choosing regulators at Dive Gear Express, make your decisions based on considerations that are less about "performance" and more about matching the regulator to the diving application. For example, an extreme exposure (i.e. deep and cold) technical diving regulator is a poor choice for shallow tropical sport diving. Beyond the features of the regulator itself, you should consider the supplier along with how the model was designed and has been supported. As an independent servicing dealer, we stock complete regulator packages, components and parts with online ordering and same day shipping.

With one exception, all the diaphragm regulators we sell are environmentally sealed, including the DGX Gears D6, Dive Rite XT1, Mares 28XR, and Apeks XTX series (DS4, TEK3, DST, FSR) first stages. The Poseidon Xstream is a unique balanced rolling diaphragm ball valve design that is not environmentally sealed because it relies upon a built in thermo-dynamic anti-freeze system to remain ice free.

Piston regulators are not typically described as environmentally sealed in the conventional sense because the internals are protected by other methods inherent in their design. The DGX Gears XTRA & FIRST, Dive Rite RG5400, and Mares R2XR are piston first stages.

The need for sealing a first stage is not relevant to most types of diving, for more information read our TekTip titled Environmentally Sealing SCUBA Regulators.

The current XTX series first stages differ in the orientation of their ports and cosmetics. Although their price varies, they are all over-balanced diaphragm design with an environmental seal and they all use the same periodic service parts kit. All the Apeks regulator packages are EN250 certified to a depth of {660 fsw | 200 msw} and have identical extreme performance breathing characteristics that make Apeks XTX regulators a popular choice of experienced sport and technical divers worldwide.

For a deeper explanation of all the model variations read our TekTip Apeks XTX Series First Stage Differences.

The current Apeks XTX series second stages are all identical except for cosmetics and one minor feature. Although their price varies, the XTX series second stages are a pneumatically-balanced downstream design with a large ergonomic venturi control lever, can be reconfigured to reverse the side of the hose inlet (left or right), and they all use the same periodic service parts kit. All the Apeks regulator packages are EN250 certified to a depth of {660 fsw | 200 msw} and have identical extreme performance breathing characteristics that make Apeks XTX regulators a popular choice of experienced sport and technical divers worldwide.

For a deeper explanation of all the model variations read our TekTip Apeks XTX Series Second Stage Differences.

Popular for stage/deco/sidemount technical diving applications, the ambidextrous and reversible second stage regulator designs ultimately offer the same feature: the orientation of the hose inlet and thus the hose routing can be either the typical right-hand side or the uncommon left-hand side of the diver. The difference is how this reorientation is accomplished.

In the few second stage designs that are reversable, the regulator body is opened, the inside components are removed, reoriented to the opposite side and the regulator is reassembled. Both the Dive Rite XT series and Apeks XTX series second stages are reversable. The Dive Rite XT series second stages require a mirror image part for the venturi be exchanged to accomplish the reversal. The Apeks XTX series second stages do not require any additional parts for the reversal. Both Dive Rite and Apeks describe the process of reconfiguring the regulator as both quick and simple, however they also both recommend this be done by a regulator technician. It takes our experienced reg tech about 15 minutes to do the reverse and bench test, if you don't interrupt them with any questions.

Ambidextrous second stage designs are inherently right or left when you simply put the regulator in your mouth. The design of the regulator is symmetric about its longitudinal axis; the body and mouthpiece has no "top and bottom" or "up and down". The exhaust on an ambidextrous design will always be on the end the body directly opposite the hose inlet and bubbles come out the end not the bottom. Ambidextrous regulators are typically referred to as side-breathers and we offer the SXS downstream second from Mares plus the Xstream upstream second from the OG of side-breathing regulators - Poseidon.

The Apeks XTX second stages (XTX40, XTX50, XTX200) are a reversible design that can be converted from a standard right-hand hose inlet configuration to an uncommon left-hand configuration. However, the Apeks distribution center in the US does not stock the XTX series reversable second stages from the factory in the left-hand configuration. Apeks describes the process of converting the regulator to a left-handed hose inlet as both quick and simple, however they recommend this be done by a technician trained to service Apeks products.

Because we do the reconfiguration in our facility using our Apeks technician, there is a small increase to the price of the Apeks XTX series standard second stage to cover the cost of converting and testing the now left-hand second stage prior to shipping. If you want to learn about what is involved, you can read the Apeks technician instructions at Converting the XTX Regulator to Left Handed Configuration.

The manufacturers of all the general purpose SCUBA regulators we stock describe them as suitable for use in warm, temperate and cold water conditions. Based on testing standards we define those water temperature ranges as follows:

• • Warm water is greater than {68°F | 20°C} to a maximum of {90°F | 32°C}.
• • Temperate water is between {68° to 50° F | 20° to 10° C}.
• • Cold water is less than {50°F | 10°C} to a minimum of {40°F | 4°C}.
• • Freezing water conditions below {40°F | 4°C} incurs significant additional risk that requires specialized training and specialized equipment.

Among the regulators we stock, only the Xstream series is described by Poseidon as suitable for diving under ice in freezing seawater conditions down to {29°F | -2°C}. However, the XTX series is a close second, described by Apeks as suitable for use down to {36°F | 2°C} and a popular choice among "ice divers".

In the 90's some regulator manufacturers (notably Apeks, Aqualung, and Mares) started offering some versions of their first stages with an oversized 1/2" low-pressure port. The oversized port has an optimized gas flow path and should be used to supply the primary second stage. (Mares calls it a DFC port.) While the oversized and optimized port does slightly improve machine test results in simulations, most divers found it does nothing significant for actual in-water breathing performance and also inconveniently requires a non-standard regulator hose.

Today, most manufacturers have deprecated their oversized port on first stages for the recreational market, although it continues to be available on versions for the military market. If you are seeking a 1/2" regulator hose, instead your best strategy might be to just plug the oversized port and use one of the other standard size low-pressure ports. If you insist on a regulator hose with a native 1/2"-20 UNF fitting, then take a look at these non-standard regulator hoses.

First stage regulator ports:
7/16" port = HP
3/8" port = LP (or IP)
1/2" port = MP

First stage regulator pressure:
high-pressure = HP
low-pressure = LP, IP, or MP

"Low" is sometimes called "Intermediate" or "Middle" pressure and all three terms are referring to the exact same regulated output pressure of the first stage.

Scuba hose connectors
second stage 9/16" = LP
inflation Shrader = BC

Mated fittings that can be quickly disconnected without tools = QD

The typical intermediate pressure setting for most first stages is around {135 psi | 9.5 bar}. Upon request a Dive Gear Express service technician will adjust the IP to your specified non-standard setting prior to shipment but only for diaphragm first stage designs. We also offer 3rd party modifications to the Apeks DS4 to change the behavior of the intermediate pressure; enabling use with constant mass flow orifices and needle valves found on some types of rebreathers.

The IP adjustment on diaphragm type first stages is simple enough for most divers to learn to do themselves. The IP adjustment screw is located under the environmental seal cap on the bottom of the regulator. The only tools needed are a round surface spanner wrench to remove the cap, a hex key set to turn the adjustment screw to change the IP setting, and an IP pressure gauge to measure the setting. These are all available in our Regulator Service Tools category. A few minutes with a knowledgeable peer or Google will show you how.

YES! Dive Gear Express offers regulator service on all models we currently sell. Dive Gear Express is an authorized service center for Apeks, Dive Rite, Mares XR, and Poseidon regulators. We of course also provide service for our house brand DGX Gears regulators. For all the details visit SCUBA Regulator Maintenance Service at Dive Gear Express.

For regulator brands that we are not certified to service, we recommend using a factory authorized service center nearest you. Three long established U.S. based companies that specialize in factory authorized regulator service for most brands are Airtech in North Carolina, RegTech in Wisconsin, and Pacific Scuba Repair in California.

The only difference between our unbranded SPG "brass & glass" models and similar branded SPG models is the logo and price; any SPG will work on any regulator regardless of brand and they are all manufactured by Termo Industra of Italy with equal quality construction. Our unbranded generic SPG models have a lower retail price as a result of being sourced directly from the manufacturer. Our long experience with the unbranded and branded "brass & glass" SPG models has been they all have similar reliability and durability in the field. Regardless of brand, every product we sell is backed by Dive Gear Express 5-star quality customer service. For more information see our TekTips titled SPG Depth Ratings and Inside Submersible Pressure Gauges.

The only significant difference is the branding and price; any DIN-to-Yoke adapter will reliably work on any DIN regulator regardless of brand. The designs differ a little but they are all of equal quality chromed brass construction. The generic value priced DGX adapters are available in your choice of black or silver color, and features a nice sized handwheel which makes it easy-grip to install and remove from the valve.

Yes and no; this simple question has a complex answer because there is no widely recognized scuba diving standard for what constitutes suitability for oxygen service. Hypothetically, the equipment we sell could be used with oxygen if we describe it as Nitrox Ready, otherwise you should assume air only service. However, from the point of view of stringent U.S. aerospace guidelines and Compressed Gas Association handling standards for oxygen, nothing in general use in recreational diving is suitable for oxygen service. Using oxygen for diving requires you to make an informed decision to accept for yourself the risks of handing the oxygen. To help form your opinion about the answer read our article About Oxygen Disclaimers.

According to our suppliers, their Nitrox Ready products are oxygen compatible and oxygen clean from the factory, prior to initial use, for compressed gases greater than 23.5% oxygen. (Air is defined as containing from 19% to 23.5% oxygen.) However, most suppliers in the dive industry specify their Nitrox Ready products for use with gas mixtures containing a maximum of 40% oxygen as the upper limit. Although controversial, some dive industry professionals are of the opinion that Nitrox Ready products do not have to be dedicated to oxygen service and may be used interchangeably with CGA Grade "E" air as long as the Nitrox Ready product never contacts gas mixtures in excess of 40% oxygen.

To better understand the issues associated with handling oxygen rich compressed gas, please read Understanding Nitrox Ready.

The 40% specification has become widely used in the recreational diving industry to reduce risk to safety of the diver and limit manufacturer liability, yet indicate a product is (at least initially) oxygen compatible and oxygen clean. For more information please read About Oxygen Disclaimers.

Since Air is defined by the CGA as containing 19% to 23.5% oxygen, describing nitrogen-oxygen gas mixtures up to 23.5% as Nitrox is just an obscure way of describing ordinary Air. Gas mixtures greater than 23.5% oxygen are what most people assume to be Nitrox, and of course there is also pure Oxygen. To avoid conflict with various dive supplier labeling and any misunderstanding about exactly what constitutes Nitrox, Dive Gear Express sometimes uses the phrase "suitable for service with compressed gases containing greater than 23.5% oxygen" to describe products that are both oxygen compatible and oxygen clean prior to initial use, especially in reference to cylinders and valves.

There are several versions of a dive tank VIP decal for sport Nitrox & Oxygen service that is widely available to anyone who wishes to purchase them online from Amazon and eBay. They typically have a punch out described as "cleaned for PREMIX oxygen content 22% to 40%". We will be blunt and clearly state these decals are meaningless; they have no provenance and reference no standards as well as being dangerously inaccurate. Local dive shops following best practice will not normally honor this type of VIP decal.

"Oxygen clean" is described as: the flow path and material surfaces which meet standards for absence of contaminates that can become a source for ignition. There are no diving-related industry-wide consensus or peer reviewed standards for the handling of the specialty compressed gases used in diving. So the dive industry has to fall back on the standards and guidelines of other industries. In the US, they are established and maintained primarily by the Compressed Gas Association (CGA). The CGA states that equipment and systems handling any gas in excess of 23.5% oxygen by volume shall be cleaned as if the gas was PURE oxygen. The CGA pamphlet G4.1 "Cleaning Equipment for Oxygen Service" describes the methods for cleaning and then testing the cleanliness of equipment used with oxygen.

Our suppliers tell us their cylinders and valves are oxygen clean from the factory. The CGA states that equipment handling any Nitrox mixture in excess of 23.5% oxygen shall be cleaned to their standard as if the gas is 100% oxygen, there is no lesser standard. That means all SCUBA tanks sold and assembled by Dive Gear Express that we label as Nitrox Ready on our VIP decal, prior to initial use, are oxygen clean from the supplier; we have done nothing to change that condition. Nitrox Ready tanks are not just 'kinda sorta clean' or 'premix clean', they are oxygen clean to CGA standards. For more information please read About Oxygen Disclaimers.

In rare cases, a shop will insist on some form of after-market "cleaning" before agreeing to fill a tank not sold by them. They have that right, but we want you to know that no such service can make a new empty cylinder and valve marked Nitrox Ready from Dive Gear Express any more oxygen clean.

Our suppliers tell us their equipment described as Nitrox Ready is already oxygen clean from the factory. The Compressed Gas Association standards state that equipment handling any Nitrox mixture in excess of 23.5% oxygen shall be cleaned to their standard as if the gas is pure oxygen, there is no lesser standard. That requirement is why Nitrox Ready equipment has already been oxygen cleaned by the manufacturer. SCUBA equipment is labeled 'NITROX READY' or '40% MAX OXYGEN' instead of 'Oxygen Service' because the manufacturers are managing the risks, both to your safety and their liability, associated with oxygen-related fires and explosions by specifying their SCUBA products for use only with breathing gas mixtures no more than 40% oxygen.

Nitrox Ready and Oxygen Service equipment from our suppliers is not just 'kinda sorta clean' or 'premix clean', it is oxygen clean. The practice by shops and individuals of aftermarket cleaning for new dive equipment that is already oxygen clean from the factory is pointless at best and dangerous if done improperly. Prior to initial use, no amount of aftermarket cleaning can make a Nitrox Ready product more oxygen clean nor can cleaning it ever override the manufacturer specified limits. The manufacturer can't stop you from using their equipment with breathing gases and pressures that exceed their specifications, but doing that requires you to make an informed decision to accept for yourself the risks of handing the oxygen.

Our oxygen compatible O-rings are typically made of fluorocarbon elastomer (aka fluoroelastomer, aka FKM, aka FPM) A-Type material. FKM is the designation for a class of fluorocarbon based synthetic rubbers as defined by ASTM standards, equivalent to FPM by ISO standards. Originally developed by DuPont under the name Viton, FKM is a high performance elastomer with excellent resistance to oxygen. In a few specific cases our O-rings might be described as made from a different oxygen-compatible material, for example EPDM.

Many people refer to any and all oxygen compatible O-rings as "viton" in the same manner that the Kimberly-Clark brand name Keenex has become synonymous with tissues. However, Viton™ is now The Chemours Company trademark brand name for their fluoroelastomers and use of the brand name requires joining their licensing program. Chemours is not the only company that manufactures FKM products and there are different types intended for various different applications. Counterfeit and mislabeled FKM A-Type material O-rings are so widespread that Dive Gear Express makes up our own kits using O-rings supplied through trustworthy channels. We use the generic terms fluorocarbon elastomer or FKM to describe our O-rings, not the brand name Viton.

There is no reliable visual inspection method to determine O-ring material composition, only specialized materials testing equipment can make that determination. Acrylonitrile butadiene rubber elastomers (aka NBR, aka Nitrile, aka Buna-N) are considered to have good resistance to oxygen with a 15 year shelf life. Fluorocarbon elastomers (aka FKM, aka FPM, aka Viton™) are considered to have excellent resistance to oxygen, with an essentially unlimited shelf life. To ensure specific composition, O-ring material must be specified at time of purchase and then segregated from other O-rings.

There are no O-ring color coding standards and thus color or appearance is not an indication of the material or quality. O-rings are available in nearly any color, although most commonly seen in black regardless of material. Even though most fluorocarbon O-rings are black, the loose FKM O-rings sold by Dive Gear Express are oxygen compatible and usually brown or green; simply to make them easily distinguishable from more common NBR O-rings which are usually black. However, O-rings inside equipment (valves, regulators, hoses, service kits, etc.) are almost always black regardless of material. O-ring materials also can not be distinguished from each other by their surface appearance, more a function of the manufacturer than the material. NBR is incorrectly said to have a shiny surface and FKM a matte surface. This is not a reliable indicator, and certainly not true if the O-ring has been lubricated.

Just to be clear, the COLOR and SURFACE APPEARANCE of the O-ring is MEANINGLESS regarding their compatibility with oxygen.

Yes. Many divers are surprised to learn the SCUBA industry convention of using fluorocarbon elastomers (FKM or FPM, aka Viton™ o-rings) with Nitrox is not a matter of oxygen fire safety. The introduction of Nitrox in recreational diving included a recommendation to use FKM for seals in gas blending equipment whose wetted surfaces contact pure Oxygen. This was frequently confused with the very important safety requirement for oxygen cleanliness (i.e. the absence of readily combustible materials); creating a mistaken but widely held belief that FKM is also somehow related to safety of Nitrox for diving equipment such as SCUBA regulators and cylinder valves.

FKM is no more 'safe' in Nitrox diving applications than ordinary synthetic nitrile rubber (NBR aka Buna-N). While FKM has a slightly higher temperature of ignition at {~ 900°F | 500°C} than NBR at {~ 750°F | 400°C}, nearly any material can still serve as fuel in the kindling chain to an oxygen fire that will reach {~ 5000°F | 2700°C}. The reason for preferring FKM in high oxygen content applications is because the service life is typically longer than NBR, i.e. FKM is more resistant to oxidation than nitrile rubber although FKM also exhibits a tendency to swell slightly in high-pressure oxygen. While FKM o-rings theoretically outperform NBR o-rings, in practice there is no safety reason to prefer them in Nitrox SCUBA life-support applications such as regulators and valves given the periodic service requirements of such equipment.

Regardless, Dive Gear Express specifies oxygen compatible and oxygen clean products whenever possible, and we only use O2 compatible O-rings and lubricants in equipment service. Any products we identify as Nitrox Ready or Oxygen Service will meet industry standards for both oxygen compatibility and oxygen cleanliness prior to initial use.

The short answer is NO. The longer answer is it depends on the exact product formulation and gas pressure but as a practical matter the answer is still no. Silicone "grease" is a generic term for a variety of lubricant formulations that are based on some form of pure silicone oil, most commonly polydimethylsiloxane (PDMS). While pure PDMS itself is a chemically inert inorganic substance that is not combustible; in order to make the little tub or spray can of generic 'scuba lube', the PDMS is mixed with thickeners and/or organic solvents that typically are readily combustible. Lubricant contamination in high pressure compressed gas equipment is a frequent cause of oxygen fires. In general, lubrication in oxygen service applications should be avoided whenever possible. Oxygen service applications in SCUBA that require lubrication must use specialized (and relatively expensive) lubricants, typically based on polytetrafluoroethylene (PTFE) or polychlorotrifluoroethylene (PCTFE) compounds.

It is true that in low pressure Nitrox applications such as regulator second stages and rebreather loops, the type of lubricant is pretty much irrelevant to oxygen fire safety. Occasionally, the desire to minimize use of expensive oxygen compatible lubricants can lead to the erroneous assumption that inexpensive silicone lubricants might used in ambient or low pressure applications that are in close proximity to high pressure applications. However, the high tack and adhesion property of silicone lubes also makes them very migratory and difficult to completely remove. In practice, we find silicone lubrication on the low pressure side of equipment will eventually be transferred to the high pressure side such as a first stage connector or valve outlet. Never use silicone lubricants with electrical contacts, even though this is an often suggested practice. Silicone products will react with plastics and other contaminates to form insulating films and silicone carbide compounds which can cause intermittent connections in low-current applications such as rebreather oxygen sensors. When multiple lubricants are available, there is also the very real increased risk of inadvertently applying the wrong lubricant. In practice, if lubrication is required it is best to only use oxygen compatible lubricant consistently throughout all equipment in service with Nitrox regardless of pressure.

Dive Gear Express avoids silicone lubricants in our facility, using only oxygen compatible lubricants for all SCUBA applications that require lubrication. Any products we identify as Nitrox Ready or Oxygen Service will meet industry standards for both oxygen compatibility and oxygen cleanliness prior to initial use.

DOT regulations currently limit the oxygen fill pressure of aluminum and composite cylinders to 3,000 psi at 70F. There are no similar DOT fill pressure limits for compressed oxygen gas in steel cylinders, but as a practical matter pure oxygen fills exceeding 3,000 psi are highly unlikely, regardless of cylinder composition or service pressure. In the US, almost all bulk compressed oxygen available to local dive shops is aviation grade in steel DOT-3AA-2400 cylinders with a CGA-540 valve at a service pressure of 2,640 psi. Since most oxygen fills by local dive shops are done using the cascade method, a typical local dive shop pure oxygen fill in a rebreather or decompression cylinder will be between 1,800 psi and 2,400 psi unless the shop has an oxygen booster.

The DOT considers any gas containing more than 23.5% oxygen to be pure oxygen for the purposes of handling. Thus, knowledgeable fill station operators will not fill aluminum cylinders with Nitrox higher than 3,000 psi. This means the 3300 psi "compact" or "neutral buoyancy" aluminum SCUBA cylinders will receive a short fill. Again, there are no such restrictions on Nitrox in steel high pressure SCUBA cylinders with a service pressure of 3442 psi. Although there are some older steel SCUBA cylinders with a service pressure of 3500 psi, recent DOT regulations limit the transport of such cylinders to a maximum fill pressure of 3442 psi as well.

We offer two different gas boosters suitable for applications with recreational diving; both are compressed air driven, air cooled, non-lubricated, reciprocating piston, single action single stage type. The DGX Gears X-30 is a value priced oxygen booster that is suitable for light duty usage. The faster Haskel MSB-9000 is a premium quality oxygen booster manufactured in the USA that is suitable for heavy duty usage in mission critical applications. A benefit of the Haskel booster is additional cooling provided by routing the cold exhausted drive air through a jacket surrounding the gas compression barrel.