I defy any divers of average ability not to feel at home in side-slung tanks within 10 minutes of trying them, and wanting to run out to buy their own! So says Scott Bisset, proprietor of Deep Blue Dive Centre in Tynemouth, who was at first sceptical when he sampled the side-mounting system on a TDI cave-diving course I ran last year.
That was until I tried it in the water, he says. Side-mounts are not solely for use in caverns and caves but are extremely effective for anyone serious about wreck penetration or any overhead environment. And, he might have added, for any diver with back trouble or who wants to feel that bit safer.
When a divers cylinders, regulators and gauges are configured at his side rather than on his back, he is using side-mounting, a concept that came from the cave-diving world. By streamlining the position of the cylinders, one either side of the body, it is possible to pass through extremely low sections, less than half a metre in height.

The Potential for confusion
Cave-divers in Britain began side-mounting their equipment in the early 1960s. Initial trials employed a single bottle, slung between armpit and thigh by a belt attached to one cylinder band. The divers lead was usually attached to a separate belt, to which the battery pack for the underwater lighting was also sometimes clipped.
This worked well, but as cylinders increased in size they tended to slip from the required position towards the chest.
In the early 70s, a fully redundant system was commonly used, with the diver having three belts around his waist. This could give rise to confusion, and the system was still prone to cylinder movement. So, a few years later, divers began to experiment with a single, more substantial, waistbelt system which held the bottles firmly in position.
In the early 80s the Troll Harness appeared, with shoulder straps to ease the burden of carrying the weight above water. Any size of cylinder could now be used.
The harness was a vast improvement over the previous system of belts, but other problems had yet to be resolved. As the bottles were secured against the divers body at a single, narrow point, using a metal cylinder band, they tended to swivel, especially as they became depleted. This could result in the cylinder valve and regulator first stage catching the floor of the passage, stirring up sediment and so on.
Perhaps the greatest concern was that the cylinders could not be easily disconnected from the harness, certainly not under water.
However, a number of divers still use this system today, and it is worth noting that the record traverse dives undertaken in British caves in the late 70s and early 90s used this basic configuration.
Another problem with the Troll Harness was that the cylinders, regulators attached, were built into it on dry land, and it was often a struggle getting to ones feet and then shuffling awkwardly to the water.
Backstrain was a common complaint. In the early 90s, US divers came up with subtle modifications, and it is to the resulting system that most British cave-divers now subscribe.

Cylinder Parallel positioning
The American side-mounting system removed much of the physical stress encountered on entry and exit from the water.
The diver now dresses in the harness, dons his instrumentation and makes all his last-minute preparations unencumbered by cylinders or regulators. Bottles, equipped with valves, are the last items to be attached, and these can be clipped to the body either out of the water or effortlessly at any depth.
Another major advantage is that the cylinders are attached to the diver at two points - waist and shoulder.
The favoured method of connecting the cylinder at the waist is to use a large karabiner. This is modified slightly, with the hook on the latch filed off and any screw-gate removed to ensure ease of connection and subsequent disconnection with possibly cold, gloved fingers.
A variety of fittings can be used to retain the cylinder in the armpit and shoulder area. A small accessory karabiner, or bolt-snap, is connected to a length of shock cord running beneath the armpit, and secures the neck of the cylinder valve to a shoulder ring on the harness.
The set-up feels a little looser and floppier above water than the previous system, but under water the bottles remain perfectly parallel with the body, and no longer pivot as the gas depletes.

Note Minimalist approach
For the solo diver, or one forced to kit up or dekit in awkward conditions, this rig is a real blessing. Beyond this, it gives divers the opportunity to remove one or other cylinder below water, either to negotiate a constricted section in a cave or wreck, or even to pass to a buddy who might be low on gas.
Side-mounting harnesses are commercially available but differ considerably.
There is much to commend a versatile, flexible rig. On short, shallow cave dives in the British Isles, for example, buoyancy control might not be required, so the harness will of necessity be a minimalist arrangement.
In the deeper caves of Florida, redundant buoyancy control is essential, and here a wing built in to the side-mount harness is invaluable (stab jackets or vests are suitable for supplying buoyancy control but a small wing, able to be detached, is perhaps better).

Finely balanced
Side-mounting can also be used to complement traditional back-mounted configurations, but divers in Britain, the Mediterranean and the Caribbean are today using multi-cylinder rigs as a direct extension of the side-mounted system outlined.
Side-mounting Using two cylinders of equal size on either side of the body provides a finely balanced position in the water. Provided that they are breathed down fairly equally, the trim is maintained throughout the dive.
At the outset, you might need to experiment a little with the positioning of your weights. Establishing the centre of gravity is not as easy as it is with conventional back-mounted cylinders, but neither is it difficult.
With two separate regulators you have a redundant system on which the cylinder valves are arguably more accessible than with a back-mounted manifold. In effect your buddy is right there by your side!
Because you are swapping mouthpieces on a regular basis, you are constantly checking the condition of each system, which does wonders for the confidence. In terms of overall safety, this is far better than carrying a pony bottle.
The system is used to best advantage with short high-pressure hoses, although it is perfectly easy to stow the excess beneath bungee or snoopy loops.
Care needs to be taken to ensure that the routeing of hoses is neat and orderly, and to ensuring that both mouthpieces are always instantly accessible. An elasticated, quick-release Fastex connector will hold the regulators conveniently close to the neck. In an emergency out-of-air scenario, the quick-release fastening on the donors regulator does not need to be disconnected, as the elastic will slide down the length of the hose.

The Easy on the back
Like anything tried for the first time, the arrangement takes a little getting used to. In terms of comfort it will not be found lacking, and for anyone with back trouble who is concerned about carrying excess weight, this could be the solution.
I suffer from a weak back myself, and would certainly not contemplate wearing a pair of 15 litre cylinders in the traditional manner.
However, where I can walk bottles into the water separately, there is no constraint on the size of cylinders that can be worn side-mounted, and even a pair of 20 litre bottles can be deployed comfortably using this configuration.
Jim Fishback has a name that few will recognise in Britain, but he is one of the leading divers with Dive Rite of Lake City, north Florida. He has a severe disability which, were it not for side-mounting, would have forced him to abandon diving, and probably most other forms of exercise as well.
Anyone who has seen the beautiful Florida springs would understand how devastating a prospect this would be, but side-mounting allows Jim both to exercise and continue his love of diving.

Tony Pub post-mortem
I suspect that there are many divers in the community who might experience more than a little physical stress when it comes to struggling with the weight of their equipment.
And, because of the need for balance when using side-slung equipment in the recreational sphere, I would recommend a pair of lightweight 7 litre (232 bar) cylinders to anyone.
Tony Sidney, an instructor on the same TDI course as Scott Bisset, also appreciated the absence of weight on the lower back. Even after two hours under water on our first open-water session, I exited with no aches or pains, as I would have had with the back-mounted 300 bar, 10 litre twins I usually use for pleasure-diving, he says.
After the first days diving we were sitting in the pub trying to come up with a list of disadvantages for the side-mount over the back-mounted set-up. I still cant think of a single disadvantage!
I found the side-mounts easier to don and doff and more comfortable in the water than back-mounts, and I felt reassured because I could see and easily get to my tank valves.
Because I use a back-mount system anyway, I dont need to buy any type of harness, because the backplate can be used to secure the tanks close to the body.
When your dive is over, it takes seconds to unclip a side-slung set while in the water. Then you can clamber back onto the boat, or dry land, with minimal effort. Think about it.
  • One-day Side Mounting courses are available from Farrworld. Contact