Dive Prep with Jarrod Jablonski
This is an older video, but an interesting look at some of the gear used during a WKPP exploration dive. There are plenty more videos available on the GUE Divers YouTube channel.
Wrist Mounted Gauges v Console Computers
It is common in recreational diving (particularly with rental gear) to have not only an SPG, but a multipurpose console including a compass and computer, attached to the high pressure hose.
However, there are potential issues with this design and advantages to separating the console into an SPG and wrist mounted compass and computer or depth gauge.
Somewhat counterintuitively, mounting all the gauges together can discourage proper referencing. Rather than maintaining an active knowledge of each gauge, we simply glance over the console, almost instantly forgetting the readings—and being tucked away in the belt or trailing behind, often means the gauges are easily forgotten and rarely referenced at all during the dive.
Conversely, consoles can completely draw our focus, if we spend a significant amount of time referencing the one combined unit. This can be dangerous, leading to a loss of buoyancy or situational and team awareness.
Consoles are also cumbersome and often left dragging behind to damage the environment. Even when tucked away in the belt they can be an entanglement or environmental hazard. Either way, they reduce streamlining, causing drag, decreasing propulsion efficiency and increasing breathing rates.
By contrast, splitting the console into its components: SPG, compass and computer or depth gauge we avoid these issues.
Every few minutes we can reference our SPG, compass and computer individually. This small group of tasks is less likely to consume our focus allowing us to maintain control and reference the up line, our surroundings and our team between each reading, while simultaneously encouraging those readings to be more effective by breaking the task into smaller manageable units.
Breaking the console into components also greatly reduces drag and the likelihood of entanglement or environmental damage, by letting us replace the console with a small SPG and stow it out of the way, attached to a shorter hose.
By wrist mounting our compass, navigation becomes easier. We no longer have to hold a large console out in front while trying to maintain awareness and effective propulsion.
Perhaps the biggest advantage comes from wrist mounting our computer or depth gauge. We can easily maintain our decompression stops, use a scooter or keep good contact with our team and environment, all while periodically referencing our depth and time.
While a console has business advantages for rental equipment, there are great diving benefits gained by separating it into components.
The Goodman Handle
Commonly, any handle used on a canister light head is referred to as a Goodman handle. However the design and purpose of the Goodman handle is very specific and many fall short of these requirements.
In the 1970’s Bob Goodman, a Florida local, designed a hand mounted light that allowed divers to retain full use of their hands—very important in caves where it can be necessary for divers to pull their way through high flow sections. The other main advantage is the ability to use both a primary light and primary reel with the same hand—which was increasingly important as the use of scooters during exploration became common place, allowing divers to use a primary light, reel and scooter simultaneously.
Goodman handles must be rigid. While the primary light is usually on the left hand, it is sometimes necessary to temporarily switch hands, e.g. to dump gas, reference an SPG or retrieve something from the left pocket. The rigid handle allows the light to be moved into the right hand (holding it by the ballast) and then quickly and efficiently replaced on the left hand. Soft/elastic handles, while feeling secure when in place, make this more cumbersome and time consuming, requiring the strap to be wiggled back over the left hand.
Another important property of a Goodman handles is a flat low profile metal frame. This allows the frame of an exploration reel to sit flat against the Goodman handle in the palm of the hand and is very stable. The round handles found on many lights need to be ‘held’ by the fingers, reducing dexterity and full use of the hand and are very unstable when used with a reel.
Many explorers add a thumb loop to the light head which allows the right thumb to hold the light if required. Thumb loops are excellent for scooter diving when the fingers of the right hand are in use but the thumb is available.
So that’s it! A Goodman handle has a rigid and flat, low profile metal design for maximising utility in various situations and to maintain dexterity and use of the hands.
The Submersible Pressure Gauge
The Submersible Pressure Gauge is vital piece of equipment for every diver—functioning as a cylinder contents gauge, much like the fuel gauge of a car.
Most people learn to dive using a console containing an SPG, a compass and either a computer or depth gauge. Superficially, this seems like a good idea, keeping all those handy instruments in one place. However, there are some serious drawbacks to such an approach.
Multipurpose consoles are large and cumbersome, often dragging along the bottom or catching on coral or wrecks. In an overhead environment stirring up silt could be disasterous, reduced visibility leading to disorientation or worse. Ask yourself how often you have seen a console dragging along, impacting the environment and out of reach when needed.
The computer or depth gauge and compass are better positioned on the wrist where they are easily referenced without subsuming your entire focus and unable to impact anything—leaving only the SPG on a shorter, cleanly stowed high pressure hose.
SPGs are best made of brass and glass. Plastics are easily broken and scratches on a plastic facing can make the gauge difficult to read. On deep dives plastic can even flex inward causing the needle to stick and the gauge to read incorrectly. A brass and glass SPG withstands higher pressures at depth and gauges manufactured this way tend to be of a higher quality and more accurate.
High pressure hoses are usually around 36”/92cm, an excessive length that bows out from the body, causing additional drag and potentially snagging. Ideally, a high pressure hose should be 24”/61cm and clipped off to the left hip using a stainless steel bolt snap. Stowed this way the SPG and hose are streamlined and protected. Like anything, practice is needed to become proficient at quickly unclipping and reclipping the SPG when referencing it.
The bolt snap should be fastened to the SPG with cave line, allowing it to be cut away in the unlikely event the bolt snap jams. Using cave line instead of o-rings or zip ties is far less prone to unexpected breaks.
The connection between the SPG and high pressure hose contains a tiny swivel pin sealed by two tiny o-rings. These o-rings wear over time and the degradation is accelerated by salt, grit and sand. Consequently, you should keep your SPG clipped off and out of harms way when not reading it. With the SPG safely stowed, we also no longer need a rubber boot protecting it. These boots seem like a good idea initially, but actually trap salt, grit and sand, simultaneously degrading the swivel pin o-rings, while hiding any damage and potential leaks.
Configuring your SPG this way simplifies your equipment, makes deploying and referencing the gauge clean and easy and keeps the SPG safely tucked away, minimising drag and damage to both it and the environment—all contributing to a more pleasant, comfortable and safe diving experience.
Hose Logic, Part III: Routing
As we saw in parts I and II, as GUE divers we use a long hose for our primary regulator and that regulator, the one we’re breathing, is the one donated in an out of gas situation. Part II highlighted some of the reasons for this:
It eliminates the possibility of donating a gas inappropriate for the current depth.
We ensure the diver in need of gas gets a functioning regulator. If your backup is fouled or otherwise not functioning properly, you are much better placed to deal with the situation than the already stressed, out of gas diver.
Formalising the procedure ensures consistency, whether breathing back gas, stages or decompression bottles, and with practice donation becomes a conditioned response—allowing pre-emptive action at the slightest hint of a problem.
Panicked divers will often attempt to grab the regulator in your mouth anyway. Accommodating this possibility avoids confusion and compounding the problem.
Using the long hose gives both divers room to move and manoeuvre, helping calm and control the situation.
It becomes easy to restow the long hose after deployment. Trying to restow a long hose that is bungied to a tank or otherwise not easily reachable or deployable, can be quite time consuming and challenging.
Consequently, the long hose is run from the right post:
The right post won’t roll off when impacting an overhead. At worst a significant impact will jam the post in the on position. If the long hose were running from the left post the opposite would be true. An impact would roll the post off, possibly jamming it in that position. Needless to say this stops the gas supply to the out of gas diver and could be fatal—the out of gas diver having no way to reopen the donating diver’s right post and the donating diver potentially being unaware of the problem—particularly while negotiating a restriction in single file (the original reason for the long hose).
Conversely, a left post roll off will be noticed immediately by the donating diver as their backup regulator would become difficult to breath or stop supplying gas altogether. If the post becomes jammed and the donating diver is unable to reopen it, they have access to a tertiary backup and can start breathing from their wing inflator by depressing both the inflate and dump buttons simultaneously. An option not available to an out of gas diver, no matter their routing.
While not as important as 1., this routing allows the long hose to run naturally from the first stage down the side of the tanks, across the front of the diver’s body, behind the neck and into the right side of the second stage, where most standard second stages feed from. Running the long hose from the left post would necessitate an abrupt change in direction, tight bend in the hose or a left feeding second stage to accomplish the same thing.
The LP inflator hose is also fed from the right post:
Running the LP inflator from the same post as the primary regulator gives immediate feedback if the gas flow to the inflator in interrupted—the diver’s primary regulator would also stop delivering gas. Placing the LP inflator on the opposite post to the primary regulator introduces the possibility of a gas delivery failure to the wing going unnoticed until needed—a potentially dangerous situation, considering emergency scenarios that may require immediate inflation.
In the event of a stuck inflator, disconnecting the LP inflator hose to prevent uncontrolled ascent is undeniably effective. However, it is not always possible, e.g. when a loss of intermediate pressure control in the first stage (high pressure seat failure) causes ice to form around the quick disconnect. If the LP inflator can’t be disconnected effectively, excess gas can be dumped from the wing with the left arm, using the rear dump valve (on the left of most wings), preventing a runaway ascent, while simultaneously shutting down the right post with the right arm. Running the inflator from the left post would make this impossible.
Feeding the LP inflator from the right post runs the hose behind the diver’s head. Gas flow through hoses, particularly when using helium, is audible at depth, and serves as another indicator of possible problems, e.g. leaks.
As mentioned, the LP inflator is a tertiary backup regulator. By feeding it from the right post we ensure that it is always available, never rolling off, and can be used by the donating diver if their backup fails or left post rolls off. Both divers can then still breath from the right post.
The backup regulator, hanging on a bungie necklace just below the chin, runs from the left post:
Splitting the responsibility between two first stages, ensures a redundant gas supply. The backup can be hung with the mouthpiece pointing up, allowing the diver to grab it without using their hands.
The SPG is fed from the left post:
The probability of a first stage failure is highest for the primary regulator—the stage with the greatest demand. Having the SPG on the left post ensures it remains relevant for the greatest length of time.
If the isolator happens to be closed, e.g. failing to run through the appropriate pre dive and pre filling checks, the indicated pressure won’t fall over time, giving the diver timely feedback that there is something amiss.
DPVs/scooters are typically operated with the right hand, leaving the left to manipulate the LP inflator, drysuit inflator, nose for equalisation, light head for signalling, reel, etc. Running the SPG from the left post gives the diver the same freedom to check it, without letting off the trigger.
GUE divers use a similar hose routing for single tank diving as well. However, for obvious reasons we run everything from a single first stage—with a standard right post style valve, i.e. no roll offs. While clearly losing some redundancy in a single tank setup, maintaining the same overall hose routing ensures consistent responses and equipment configuration for all of our diving.
Hose Logic, Part II: Why We Use a Long Hose
The principle of the long hose is what finally convinced me to undergo GUE Fundamentals training—after seeing other GUE divers in the water and thinking: “Man, I want to look that good in the water”. Working as an instructor and guide in the Caribbean, I occasionally assisted out of gas divers. Swimming while connected to another diver by a standard octopus hose is uncomfortable to say the least, but more importantly: ineffective.
GUE teaches an alternative system, using a long hose—allowing divers to maintain a comfortable distance while sharing and making their way back to their exit.
The long hose system involves having your primary regulator on a 5’/7’ hose and a backup regulator on a short hose running over your right shoulder and hanging just under your chin, attached to a necklace made of bungee chord. The long hose runs from the right post first stage, along the tank, around under your right arm or light canister, across your chest, up behind your neck and around into your mouth—for obvious reasons the hose is not wrapped around your neck! This method of stowing the long hose makes it trivally easy to restow if it was deployed temporarily. You wont need help stuffing the hose back into a bungee on your tank or have to otherwise deal with 7’ of troublesome regulator hose.
Originally developed for cave diving, it became clear that the long hose’s benefits apply equally to gas sharing while swimming through a cave restriction, a passageway in a wreck or side by side on an open reef—there is no real difference. Handling any out of gas situation is more comfortable, more effective and less stressful, allowing divers to maintain buoyancy and trim, while giving them room to move and manoeuvre even in the tightest of spaces.
Why The Primary?
During an out of gas situation your number one priority is to get gas to the stressed and possibly panicking, out of gas diver. Do you really want to give them a regulator that has been tucked into your BC? A regulator that may have come loose and been dragging in the sand? A regulator that may take some time to locate and donate? A regulator that may be running from a post that has rolled off? You have gas, you are calm and in control. The best course of action is to donate the regulator you know is clean and functional.
Attempting to donate your secondary regulator, introduces uncertainty and risk related to all the questions above, increasing the chance that an out of gas diver, already stressed and desperate for air, is going to reach for your primary regulator anyway. It is better to be prepared for this and deal with the immediate priority by donating your primary in the first place.
A quick dip of the head allows you to quickly and smoothly punch out your primary regulator, freeing the majority of the long hose and getting gas where it is needed. Now it becomes apparent why we call the secondary regulator a ‘backup’. It is your backup, and is easily found and popped into your mouth once you’ve donated the long hose. Being on a short hose and hanging around your neck, the backup regulator is unlikely to be contaminated with sand or silt and any leaks or free flows would have been immediately identified and remedied during the dive.
Once you are both settled, the remainder of the long hose can be deployed, any other cleanup performed and you can comfortably call the dive.
The long hose gives the out of gas diver control of the hose and lowers the risk of it being pulled from their mouth. It also gives both divers room to communicate effectively, maintain situational awareness, use effective propulsion techniques and to position themselves as dictated by the environment—try swimming single file through a restriction sharing a standard length regulator hose. Swimming on your back dragging an out of gas diver to the boat is a thing of the past!
Some divers express concern that donating their own regulator could leave them without a functioning gas supply. But if you really think this through, it is not an issue. Maintaining your equipment, using correct hose routing (see part III) and performing appropriate checks before and during the dive ensures your backup regulator is on and functional.
Learning and practising safety- or s-drills ensures we are proficient and can deal with an out of gas situation efficiently and effectively—before stress becomes panic. A skill worth learning takes refinement and your diving routine should include regular s-drill practise, whether you are an experienced or novice diver, ensuring you are a valuable team member, not just a buddy.
Watch out for Hose Logic, Part III: Routing.
Hose Logic, Part I: Lengths
One of the characteristics that define a GUE diver is our equipment configuration. It is often what draws divers to the agency. The goal of the configuration is to be comfortable, streamlined and efficient in the water, avoiding entanglement risks and unnecessary drag. An important part of achieving this goal is the hose logic, something many divers pay little attention to or conversely, overcomplicate.
This series of posts will explain GUE hose logic, starting with standard hose lengths, in part II we’ll discuss why we use a long hose and in part III we’ll explore hose routing for a single and twin tank set up.
Many divers taking Fundamentals are amazed at the difference correct hose lengths make in the water. A short backup regulator hose makes a huge difference when routed over the right shoulder, instead of hanging down or flapping around over your arm; and a long primary hose makes donating and sharing gas effortless. All the hoses are sized for streamlining—long enough for their purpose and no longer. The long hose, at first glance, can appear unwieldy, but as we’ll see in a future instalment, with proper routing a long hose is still clean and out of the way until required.
Standard GUE hose lengths:
- Primary Regulator: 7’/210cm
- Backup Regulator: 22”/56cm
- High Pressure SPG: 24”/61cm
- Low Pressure Inflation: 22”/56cm
- Drysuit inflator if using an argon bottle: 22”/56cm
A 5’ long hose may be used for single tank diving, when you have no light canister or pocket to stow the excess hose (though it can be stowed in the belt), however for any twin tank diving or diving where there are restrictions forcing the team into single file, a 7’ long hose is essential.
Some divers prefer a slightly longer 24” backup hose when using Apeks regulators, due to the port configuration, however for Scubapro Mk25, Halcyon or other similar regulators 22” is perfect.
When traveling we tend to take two 22” regulator hoses and two 9/16” male to low pressure inflator adaptors. That way the hoses can be used for the backup regulator, wing inflation or drysuit inflation.
Divers of any height can use these hose lengths, helping team standardisation and logistics, and improving comfort, streamlining and efficiency in the water.
Stay tuned for Hose Logic, Part II: Why We Use a Long Hose.
This article is an explanation of the isolation manifold diving system. I aim to introduce the uninitiated to the concepts involved and provide information so that current users may become more familiar with their chosen system. If you dive with a manifold or if you dive with a person that utilises one, you should have a thorough understanding of the mechanical workings. If a diver does not fully understand the complexities incidents are far more likely to occur.
In the early 1970’s Canadian, George Benjamin saw the need to make a simpler system to assist him with his deep diving endeavours amongst the blue holes in the Bahamas. Utilising a machining shop he and Ike Ikehara produced a manifold block, which enabled both tanks to be connected together and gas to be breathed from two posts. This became known as the ‘Benjamin crossover manifold’ and marketed commercially in the United States as an isolation manifold. There are now two common types, the barrel o-ring and the captured o-ring.
Captured o-rings are fundamentally less solid. Any twisting of the tanks potentially can break the face seal causing a loss of gas. Barrel o-ring manifolds utilise a male fitting containing 2 barrel o-rings which fit into a female fitting tank valve, which is far more secure.
Whilst utilising a manifold any leak or failure of a regulator can be addressed simply by shutting down that offending valve. Gas from that tank can still be breathed via the second regulator on the other post. Therefore any one failure is less serious as a diver still has access to the entire gas carried. In the unlikely event that a tank neck o-ring or burst disk ruptures the isolator valve can be closed saving one half of the diver’s gas. A diver could continue breathing gas from the leaking tank until it is drained.
If directly facing an individual valve on a manifold, they each turn off clockwise. That is, turn to the right to close. This quickly identifies the obvious issue as the left post, which can roll shut during the motion of swimming forward (by rolling to its right). This is less than ideal and users of a manifold system should be very familiar with this hindrance. To achieve a closed valve it requires approximately 4 full turns of the knob. This problem can be created on a left post by rubbing or rolling the valve against the roof and travelling forwards.
Similarly divers should be aware that the right post can roll shut if you were to travel backwards and rub the valve against the roof. The initial action drill/response to this dilemma is for a diver to conduct a valve check (also known as a flow check) to ensure all valves are open each time they feel their valves touch anything. This is now taught within the GUE and Cave Diving Association of Australia (CDAA) training system.
The flow check requires the diver to check each valve of the manifold starting from the right valve to the isolator and finally to the left valve ensuring each is open. This simple drill conducted regularly, will almost certainly ensure that a closed valve never becomes a problem. If a diver, during a dive, discovers a closed left post, inevitably he/she has not bothered to check their valves regularly during the dive.
Manifold Management (preventative):
- Valve check - right post/isolator/left post (right to left) at commencement of the div
- Valve check right to left if you touch any part of the cave
- Valve check right to left at gas turn point in the dive
- Valve check any time you are uncertain of their current status
Having identified the weakness of an isolation manifold as the left post rolling shut, a diver should consider what hose is the most important in his system. Without a doubt, it is the hose you are primarily breathing, enabling you to survive the underwater environment. To this end it makes sense that this hose be placed on your right post where it cannot roll off. The second most important hose in the system is your primary buoyancy inflation hose. This also is placed on your right post as you do not want to have either breathing or buoyancy issues at a critical moment.
Now, logically to keep systems redundant, your back up regulator should run from your alternate first stage on the left post and your redundant inflation system (your drysuit) should be connected to the left post as well. This enables a diver during a failure of either post to have an air supply and a buoyancy system to exit safely. In my opinion there can be no argument to this sound logic.
The remaining hose attached to a manifolded system is a high pressure SPG. Being manifolded together we require only one SPG. Unlike independent systems, which must keep track of both tanks, a manifold enables one gauge to read both cylinders pressure at one time. If the SPG fails the dive is turned. If you are diving within your gas rules there is no necessity to know your exact pressure during an emergency exit. You must have been within useable gas (e.g. thirds) and are now on your way out. Your buddy’s pressure gauge can also acts as a reference. Divers should be aware of their buddies breathing rate compared to their own.
We place our SPG on the left post for two reasons. Firstly, if the left post rolls closed the SPG is an indicator to a diver of this fact. The pressure gauge will read either very full or very empty. Very full because you are recording only the line pressure in the left post 1st stage, which has not changed since the commencement of the dive or very empty as you utilise the air in the hose to inflate your drysuit or the backup regulator purges. The pressure in the line may therefore drop to empty very rapidly but will not be consistent with your depth and time for your dive. Secondly it keeps the right post clear and enables a similar routing of the 2m long hose without the complexities of having a clipped off SPG to manage during hose donation.
Manifolded cylinders are undoubtedly the easiest to streamline as far as hose configuration is concerned. They require one less hose which is effectively one less possible failure point in a system. They are simpler to monitor and control your gas usage due to the non-requirement to swap regulators. Gas management and calculations are simpler and enable a diver to utilise the 1/2 plus 15 bar rule when utilising multiple stage bottles. The lack of all these complications make the manifold ideal for deep diving where mental calculations are more prohibitive.
If a failure is to occur, statistically manifold systems are more likely to enable a diver to exit whilst still accessing all available gas. Any single failure in an independent system renders the offending cylinder totally unusable. Independent divers can then only exit on the gas in their working cylinder.
Just to rattle some of the manifold advocates, you must be aware that there is actually a possibility of a total gas loss. In the circumstance where your isolator valve knob were to shatter and a leak to commence from the isolation valve itself or from barrel o-rings of the manifold T-piece, you risk total gas loss as you could not close the valve due to the shattered knob. This is a single point failure and most dangerous.
In an effort to reduce this likelihood rubber knobs are recommended as they are less likely to shatter rendering the valve useless and unable to be manipulated. Isolation T-pieces are also not locked off, enabling them to rotate slightly and have some give in the knob if smashed hard against the overhead.
Another negative issue is the potential to breathe a dangerous gas due to an incorrect filling process. If a dive shop were to undertake to give you a Nitrox 32 fill and after putting the oxygen into your cylinders, decide to close your isolator just in case the gas leaked over night. The gas mixer returns the next day and with the isolator closed air tops from the left post you would leave the shop with 35 bar of oxygen in your right tank and 230 bar of Nitrox 32 in your left cylinder. Your SPG would show 230 bar, analyse correct from the left post and appear OK. If however you were to breathe from your long hose (right post) you would be breathing pure oxygen risking oxygen toxicity poisoning and possible death.
Due to this potential issue, always check ALL valves are open prior to filling, diving and analysis and habitually analyse and fill your cylinders from your right post.
Lack of understanding of the mechanics of a manifold leads to ineffective problem solving. For example: You are ten minutes into a dive at a depth of a constant 10 metres. Your starting pressure was 240 bar:
- Your SPG now reads 40 bar - this indicates immediately your left post is closed and you have diminished the line pressure (by drysuit inflation or backup regulator purge/usage).
- Your SPG reads 240 bar - this indicates immediately your isolator is closed as you are breathing gas only from the right tank.
Both these problems quickly identified are easily remedied. Stop think and act. Then communicate to your buddy. Have them confirm that the issue is corrected, continue or call the dive. To this end I find it imperative that the divers I dive with have the same understanding of my system as I do. They can act in a pre-determined sequence to efficiently and quickly fix an issue before it compounds.
This standardisation, I suggest should be adopted by all divers whatever their personnel diving configuration.
Managing a real failure
If during a dive, a regulator, valve or hose fails, a diver should immediately try to identify which post is the cause of the issue and close the corresponding valve. The diver must be instinctively aware as to what closing the valve will effect within his diving system. For instance, if you identify the failure at the right post you must understand closing the valve will shut of the regulator in your mouth and you will not have gas, nor will you have BC buoyancy. You must shut the valve and swap regulators in this scenario. Once the offending valve is closed communicate with your buddy, attempt to fix the problem, and either continue or call the dive.
If you can not immediately identify the problem yourself and having shut down the valve you thought was defective, you should then isolate immediately—maintaining at least half of your gas supply. Then communicate with your buddy. Your buddy is in a far better position to assess the situation and identify the problem. He can visually rather than tactilely address the problem. This now highlights why a dive buddy should be familiar with your configuration, ideally the same as his.
A buddy needs to first see what hose you are breathing and check what valves are on and what are closed. This moment may be critical as if he/she does not understand your hose setup, things are going to get ‘mind focusing’ fast, when he/she then shuts off your remaining post! The buddy can address your problem, determine whether it is fixable then and there, or not, take required remedial action and then either call the dive or indicate he has fixed the issue. The diver should then verify what has been done to his system by checking his valves right to left, noting if any are not operational. Being able to instinctively identify what the closure of each valve means to your system is crucial at this point.
It is essential all divers are instinctively aware of how a manifold system works mechanically and what is affected by closing any valve. Both divers should be wholly aware of exactly what state the damaged diver’s valves are in and therefore what equipment functionality is, at all times. Practise valves drills (NEVER practise alone!). Become comfortable shutting down all valves in a controlled sequence and learn what the closure of each valve will affect.
Lastly, I have commonly seen independent cylinders configured with a manifold system left post on their left cylinder. Users need to understand that although this is both more aesthetic and easily manipulated, you are in effect getting the worst of both worlds. You now have a system that has the weakness of the manifold system—left valve roll off—without the benefit of being able to access all the gas.
The article originally appeared in the CDAA’s Guidelines magazine.