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Tech Diving: Backmount vs sidemount

Backmount or Sidemount
Backmount or sidemount?

Forget Fury v Joshua, the big showdown when it comes to technical diving is backmount v sidemount. Recreational diver Gavin Jones took the plunge with RAID UK Director of Training Garry Dallas to try out both forms of twin-cylinder diving. MARK EVANS reports and he took the photographs

Back in the day, when it came to open-circuit technical diving, the default “base” from which to develop your skills was a trusty twinset, either manifolded or two independent cylinders.

Having twin 10-litre or 12-litre cylinders on your back gave you ample gas and redundancy over a solitary tank to venture a little beyond “recreational” diving depths and then, by adding one or more side-slung cylinders as your training in the world of technical diving progressed, you could really start to explore those alluring depths.

Then sidemount burst onto the scene. Now, diving with two cylinders, one on either side of your body, with a streamlined wing on your back for buoyancy, was nothing radically new – cave-divers had been using this set-up for many years – but several years ago it became very en vogue, and suddenly diving sidemount on reefs and wrecks became the in thing. It also provided a stable base from which to add more cylinders as tech training developed.

Sidemount v Backmount
Sidemount set-up

So you are a recreational diver, with a few years of diving under your belt and a couple of hundred dives in your logbook, and you are looking to enter the world of technical diving. You have a choice – sidemount or backmount? 

Which to choose?

We recruited Gavin Jones, a keen single-cylinder Master Scuba Diver and RAID 40 diver from Shropshire who was showing an inclination to “go technical” in the future, to be our guinea pig and try out both forms of twin-cylinder diving.

He has trained with Shrewsbury-based RAID centre Severntec Diving, and already uses a backplate-and-wing and long hose set-up, so was well on his way to the technical dark side.

“As I progressed through various courses and my depth limits, one thing that was always at the forefront of my mind was redundant gas supply,” said Gavin. “While I acknowledged the buddy system, I didn’t want to rely on the ability and skills of an unknown diver while diving on holiday. 

“As I reached the limits of recreational diving, I opted to always carry a stage cylinder with the same gas for non-deco dives deeper than 20m, for my own peace of mind and to be self-reliant. This reduced my anxiety, gave me comfort and allowed me to enjoy the dive. 

“My first experience with a twinset was unloading our club’s van – I enquired how they managed to even stand up with that on! The reply was ‘you get used to it’, and ‘you don’t notice in the water’. Sidemount seemed easier to manage at the dive-site, but the set-up looked nothing like my backplate-and-wing, so I was sceptical if I’d be able to understand a different way of doing things.”

Sidemount v Backmount
Gavin Jones and Garry Dallas

We then roped in Garry Dallas, Director of Training for RAID UK & Malta as our mentor, to take Gavin on extended try-dives both in backmount and sidemount so that he could see the pros and cons of both forms of technical diving.

To the Delph

To The Delph
Diving at the Delph

A bright, sunny morning greeted us as we rolled into the car park at the Delph. Garry maintains a classroom there, so it made sense to conduct the try-dives at this location.

After introductions and the obligatory coffees, we went into the classroom and Garry immediately went into instructor mode, explaining the differences between backmount and sidemount, and getting Gavin sized up with the correct wings and harnesses.

Although he is well-known in sidemount circles, Garry also teaches and dives in backmount (as well as with rebreathers), so he was the perfect guide to show Gavin the ropes with both systems. First up was sidemount.


This was a new concept for Gavin. “I carried both cylinders to the water, placed them in the shallows and returned to get into my harness. I noted how easy it was to get set up, and at no point was I carrying anything heavy.

“Once the sliding D-rings were correctly positioned and the cylinders were bungeed up, the whole system was very neat and streamlined – nothing protruded wider than my shoulders or deeper than my body.”

It took a little while for Gavin to get properly rigged up with the cylinders sitting in the correct position, but at least he was used to the long-hose set-up, so that aspect of sidemount didn’t feel completely alien to him.

I know from back when I did my sidemount course with Garry that it does feel very odd to be in the water with nothing on your back, and to have the valves on two cylinders sitting either side of your chest. On the other hand, this positioning also helps you to achieve a nice horizontal trim very quickly.

One thing that Gavin did have to get used to was swapping between his regulator second stages to evenly deplete the gas out of his two cylinders. One sits around the neck on a bungee, as per normal long-hose recreational or twinset diving, while the long hose is equipped with a P-clip so that when that regulator is not in your mouth, it can be securely clipped off onto a D-ring on your right shoulder-strap.

“Keeping the gas in the cylinders balanced was straightforward and the regulator switching was not as often as I thought,” said Gavin. “I was told to keep them about 20 bar, which meant when you’d switched you could breathe the next one down 40 bar, and so forth.”|

Twinset Diving
Getting used to the feeling of sidemount

Under Garry’s watchful eye and tutelage, Gavin soon got to grips with sidemount diving. His trim and position in the water was nicely horizontal within a matter of minutes, and I could see that he was enjoying the ease of access to both pillar-valves for shutdown drills, etc.

Garry doesn’t do anything by halves, and really worked with Gavin to ensure that he got the best possible introduction to this form of diving. He also put him through several skills and drills, including back-finning, turning, and so on.

“The whole system felt very balanced, streamlined and stable, and I was able to turn and manoeuvre with minimum effort,” said Gavin. “I liked the fact that everything was right there and accessible. I could easily see and manipulate valves, check SPG and hose routeing. Entering and exiting the water was easy, and rigging up was much easier and quicker than I had envisaged.” 

A quick spot of lunch in the on-site café at the Delph and then it was time to go diving backmount.


Sidemount v Backmount
Back to backmount

Gavin immediately looked more comfortable out of the blocks with a traditional twinset on his back. As he was used to diving with a backplate-and-wing and a long-hose set-up, other than the fact that he now had two cylinders on his back instead of one everything else was very familiar.

However, there was that weight to get used to. “I’ve suffered with a bad back on and off for many years from a motorcycle accident, so I wasn’t particularly looking forward to hoisting all that weight up and walking to the water,” said Gavin. “However, I was pleasantly surprised that once I’d got it up and everything secure, it wasn’t too bad – I managed the walk and the entry to the water without a problem.”

One of the key skills when using a backmounted twinset is the S-drill, or shutdown drill, and Gavin found that there was a definite knack to reaching up and over his shoulders to turn the knobs on the cylinder pillar-valves and the central manifold knob.

Garry told him that the skill would become easier over time, as a result of muscle memory and increased flexibility, but this was the only aspect of twinset diving that Gavin appeared to find a bit awkward.

”I instantly felt comfortable with how everything was set up and worked – until we discussed and went through shutdown procedures,” he said. “In my drysuit I struggled to reach the valves to turn them. Maybe with some physio and practice this wouldn’t become an issue.”

Time To Go Diving Backmount
Mastering the techniques

Once under the water, Gavin’s trim and buoyancy in the water was very good, and he didn’t seem to have any major issues, even through all the skill-and-drill circuits directed his way by Garry.

“I liked the instant familiarity with the set-up and rig, and once on my back it wasn’t as heavy and bulky as I thought it would be,” said Garry. “However, I wouldn’t have liked trying to get out on slippy rocks or up a boat-ladder.”


So, which is best? Well, it isn’t quite as straightforward as that. As with many things in diving, it is a bit “horses for courses”. What works well for one person doesn’t necessarily tick all the right boxes for someone else.

Either set-up makes a sound starting point for technical diving. Sidemount allows a lot of flexibility – for example, it’s a simple matter to rig up one cylinder and go diving if that is a better option for a particular dive than needlessly lugging two tanks, whereas with a twinset you’re stuck in that layout. 

Likewise, you can carry your sidemount cylinders down to the water’s edge and entry-point one at a time, reducing the weight you’re having to carry in one go. Many sidemount devotees note the reduced strain on your lower back, and the enhanced freedom of movement from having the cylinders on your side rather than mounted on your back.

On the flipside, you get those who see rigging sidemount as a real faff, and prefer just being able to sling a twinset on their back and go diving.

Technical divers do tend to be tinkerers and are always fettling their kit anyway, but sidemount divers can take this to a whole new level of tweaking, so I understand this viewpoint to some extent.

Sidemount v Backmount
Despite the unfamiliarity, sidemount made an impression

Which one came out on top for Gavin? Well, he was undoubtedly more comfortable in the twinset from the outset, but he liked the flexibility of the sidemount system and towards the end of his try-dive in this rig was looking very streamlined and trim in the water.

A few weeks later, he bit the bullet and did his first course using two cylinders – in sidemount, in case you were wondering…

The gospel according to Garry

“There’s so much subjectivity regarding the pros and cons of backmount and sidemount that it’s hard to see the wood for the trees – and egos. From an unbiased point of view, given my earlier technical diving path on twinsets from diver training through to trimix instructor, seeing the differences was obvious, hence I’m still diving religiously today.

“For the past 60/70 years innovation has improved on all scuba systems, so now RAID has released, alongside the twinset, the most up-to-date sidemount training manual, the primary author being me. Fundamentally, every unit should keep you safe, redundancy being your safe, accessible back-up.

“For this main reason, sidemount cave-divers have found this configuration the safest choice. If anyone can’t – or really struggles to – reach their valves easily every time, without losing buoyancy, then they need to change configuration. Period!

“Other reasons you’ll learn on a RAID course are minor in comparison. For instance, carrying double the weight on land as opposed to singles, while your L4 and L5 vertebrae screams on the way back to your vehicle. Can sidemount be a faff? Of course, when someone hasn’t trained on it. Everything is hard work when you don’t know what you should be doing.Train ‘hard’, dive easy!”


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Abdul Hameed
Abdul Hameed
1 year ago

I am a supervisor served 26 years in Pakistan naval special Force and serving in Behrain nave last three years
I see your post and it’s very knowledgeable

1 year ago

Having worked for many years on various UK dive boats I can say, with some experience, that most side mount divers are a nightmare to deal with. Almost all of them require assistance to get into their kit, even if they don’t carry deco gas and they take-up a lot more room on the bench than a twinset or rebreather diver.

A skilled side mount diver is a pleasure to deal with but they are few and far between. Most seem to have just bought into the Kool-Aid but it adds nothing to their diving experience.

Reply to  NickB
1 year ago

How does two 12l cylinders and a stage for side-mount take up any more room than two 12l cylinders and a stage for back mount, Or even two 12 litre cylinders spread out for single tank divers ?
Also side-mount divers keep their rigging on between dives, so no backplates etc on the cylinders etc they just disconnect cylinders on exit and connect cylinder’s when entering the water, the rest is the same ….
You may be asked to help with a stage (maybe not), but even back mount and rebreather divers appreciate that little bit of help when kitting up.
It actual adds a whole
Lot to the diving experiences ,a diver is so much more streamlined in side- mount configuration than in back mount and the freedom to detach and move cylinders around inside a wreck or tight space is sometime the difference between seeing the engine room and not being able to get in there due to restrictions etc, anyway I assume you have never dived side-mount due to your comments.
Many boat crews these days moaning about twin back mount,
Side- mount etc it’s as if they don’t want the divers business and we are just a hassle to them 😂

David hamilton
David hamilton
Reply to  Scubamatt
1 year ago

Well said

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