Overview

The manifolded double tank configuration, often referred to as simply “doubles”, offers the diver a larger gas supply (2 tanks) with the benefit of redundant cylinders and regulators and the capability of having each cylinder work independently of the other, in the case of a catastrophic failure.  However, in order to maximize the full advantage that doubles offer, the first stage regulators must be configured properly.

 

When setting up your doubles regs, it’s important to keep a few points in mind;

• Use proper length hoses to ensure clean hose routing and to avoid having hoses stick out or "up" unnecessarily where they could damage (or be damaged by) the cave or wreck, or entrap the diver
•  Hoses should not have hose protectors as they collect moisture, salt and sand and serve no useful purpose
• The purpose of using doubles is to provide the diver with more gas, but also provide redundancy.  In order to offer true redundancy, each post should have a 1st stage, a 2nd stage and a buoyancy control device connected to it, unless the diver is using a separate drysuit inflation system.

Hardware

• 2 1^st stage regulators
• 2 2nd stage regulators
• 1 submersible pressure gauge (spg)
• 1 5-7' LP primary regulator hose
• 1 22-24" LP backup/secondary regulator hose
• 1 24" HP SPG hose
• 1 appropriate length low pressure inflator (lpi) hose
• 1 appropriate length drysuit inflator hose

Orientation - Posts & Valves, Primaries, Backups and Roll-offs

When discussing the orientation of the tanks, we speak in terms of how the tanks are oriented to the diver, while wearing the tanks. 

 

So, the right valve, commonly referred to as the right “post”, is the valve on the diver’s right when wearing the tanks.

 

The left post is on the diver’s left, when wearing the tanks.

 

The right post is also referred to as the primary post, meaning the hoses attached to the right post are the primary life support (2^nd stage regulator) and buoyancy control (wing).

 

The left post is also referred to as the backup, secondary or “roll off” post (due to its ability to be turned off, or “rolled” off when it contacts a ceiling while the diver is moving forward in an overhead). Since this is the backup post, the necklaced backup 2^nd stage, drysuit inflation, if no independent drysuit inflation is used, and the submersible pressure gauge (spg) all are connected to the left post.  The drysuit serves as the backup buoyancy control to the wing.

You'll notice there is no spg attached to the right post. In the Hogarthian/utd configuration, only one spg is required.  It’s connected to the left post, due to the left post's ability to roll off.  If the left post is indeed rolled off, the spg’s needle will not move as the tanks’ pressures are decreased, alerting the diver that there is an issue with the gas supply (left post closed/rolled off, isolator closed, etc).

 

Right Post

As explained above, the right post supplies the primary life support and buoyancy control. 

 

The primary regulator is the reg the diver breathes from during the dive.  It's also the regulator that is donated to an out of gas (OOG) diver.  In the event of an out of gas situation, the donor donates the regulator he/she is breathing.  This ensures the out of gas diver receives a known working regulator with a gas that is breathable at that depth.  In an overhead environment, it allows for single file exits when passing through restrictions.  In open water, non-overhead environments, it allows the divers the flexibility to facilitate a side-by-side direct or swimming ascent, or a face-to-face direct ascent, as needed.  To enable this, the primary regulator typically has a 5-7' hose (7' for overhead environment) "longhose".

 

When geared up, the diver routes the longhose (illustrated in yellow) from the right post down behind the wing, under the light canister, around the waist and up across the chest, and around the left side of the neck and into the diver’s mouth.  The excess of the hose is stowed behind the light canister or, if no canister, tucked into the waist strap or under the knife sheath.  Some wings' construction may require you to route the hose over or in front of the wing.

 

The low pressure inflator, or lpi (illustrated in blue), hose also is connected to the primary 1^st stage, since it’s the diver’s primary means of buoyancy control.  The lpi hose is routed behind the diver’s neck, along the corrugated hose, and connects to the inflator mechanism.  The length of the lpi hose will vary depending on the length of the wing’s corrugated hose.  The lpi hose length should be so that it's not so too long, where it has a large “loop”, or “pushes” the corrugated hose down, nor too short, “pulling” the corrugated hose up.

 

Left Post

The left post, being the backup or secondary post, supplies the backup life support, also called the bungeed/necklaced backup, along with the backup/secondary buoyancy control, the drysuit, if no independent drysuit inflation is used, along with the spg.

The backup regulator’s hose (illustrated in red) is typically on a 22-24” hose.  The length of the backup hose must be long enough to allow the 2^nd stage to rest under the chin when not in use and allow the diver enough freedom of movement to fully turn and look to the left when in use. However, if the hose is too long, it will rest over the right chest d-ring, making it difficult to attach or deploy equipment from that d-ring and/or may possibly trap the hose as equipment is attached to the d-ring, over the hose.

The drysuit hose length (illustrated in silver) is as needed so as it does not restrict the diver’s movement, nor does the hose form a “loop” causing unnecessary entanglement hazards or clutter.  It should be routed from the left post, under the diver’s left arm and shoulder harness.

The spg is also connected to the high pressure (HP) port of the left post first stage.  The spg/HP hose (illustrated in black) is typically 24”.  It must be long enough to allow the spg to sit over the left hip D-ring, but no so long that it bulges out or allows the spg to dangle below the diver.

 

Result

Now that we've covered each post individually, let's take a look at how it functions as a whole.

In this picture:

Right Post

- 7' LP primary regulator longhose (yellow)

- 18" lpi hose (blue) connected to a 13" corrugated hose

Left Post

- 22" LP backup/secondary regulator hose (red)

- 24" HP spg hose (black) 

- 21" drysuit inflator hose (silver)

The final product is a completely redundant gas supply system, with each post having its own 1^st stage, 2^nd stage and buoyancy control.  Should any of the diver's gear fail for any reason, he has a completely independent cylinder, 1^st stage, 2^nd stage and buoyancy control, regardless of which post he uses.  

The identification, management and resolution of failures are beyond the scope of this article and will be discussed and addressed in your FKD/UTD technical training.

Note that all hoses are routed "down", not only allowing the diver full access to the valve and isolator handwheels, but also preventing any unnecessary entrapment hazards.  Also note the lack of hose protectors on all hoses.

Right Side View

In this picture:

- Right post

- 7' LP primary regulator "longhose" (yellow)

- 22" LP backup regulator hose (red)

- Light canister (no lid attached, to limit hose/wire routing confusion)

Note how the primary regulator longhose (yellow), is routed from the right/primary post, down behind the wing and forward under the light canister.  It then comes up across the diver's stomach and chest and over his left shoulder, behind his neck and over his right shoulder to the primary 2^nd stage.  This keeps the 7' hose clean and tight, with no large loops or bulges.  This is also the 2^nd stage the diver breathes from during the dive and donates in an OOG emergency.  

Also note how the backup regulator's hose (red) is routed behind the diver's neck and over his right shoulder.  Remember, the backup/necklaced 2nd stage comes from the left/backup post.  However, the hose and 2^nd stage is still routed over the diver's right shoulder, to maintain consistency in how the hoses and 2nd stages are routed.

As shown in the illustration, there are no hoses routed "up" from the 1^st stage.  All hoses are routed down.  As addressed earlier, this gives the diver full access to the valve and isolator hand wheels, and also prevents the hoses from damaging, or being being damaged by, a cave or a wreck.  It also eliminates an unnecessary entrapment hazard by providing cleaner hose routing.

Left Side

In this picture:

- Left post

- 21" LP drysuit inflator hose (silver)

- 24" HP SPG hose (black)

- 7' LP primary regulator "longhose" (yellow)

Note how the drysuit inflator hose (silver) routes from the left/backup post, under the diver's left arm and under the left shoulder harness.  There are no loops are bulges, keeping the inflator tight and clean under the diver's armpit, eliminating entanglement hazards.

The HP spg hose (black) is routed from the left post and straight down, where the spg is clipped to the diver's left waist d-ring.  This keeps the HP hose clean, with no bulges or loops.

Also note how the 7' LP primary regulator longhose (yellow) is routed across the diver's stomach and up across his chest toward his left shoulder.  If no light canister is used, the 7' longhose can be routed under the knife sheath or simply tucked into the harness' waist strap.

Front View

In this picture:

- 7' LP primary regulator "longhose" (yellow)

- 22" LP backup regulator hose (red)

- 21" LP drysuit inflator (silver)

- 24" HP SPG hose (black)

- 18" lpi hose (blue) connected to a 13" corrugated hose

Note the 7' LP primary regulator longhose (yellow) comes from under the light canister across the diver's torso (over the drysuit inflator hose), over his left shoulder, behind his neck and over his right shoulder to the primary 2^nd stage.  This is the 2^nd stage the diver breathes from during the dive and donates in an OOG emergency.

Also note the 22" LP backup/secondary regulator hose (red) comes over the diver's right shoulder and is held in place via a bungee'd necklace.

The LP drysuit inflator hose (silver) is routed under the diver's left arm and is connected to the drysuit inflator mechanism.  Note the importance of connecting the drysuit inflator hose prior to donning the 7' longhose, to avoid "trapping" the longhose under the drysuit hose, preventing full deployment of the longhose to an OOG diver.

The low pressure inflator hose (blue) is connected to the wing's inflator mechanism.  

The 24" HP spg hose is routed behind the diver's left shoulder and is clipped to the left waist d-ring.