Question Rec cold water diver: Single, Double or Sidemount? (focus on safety)

[DAJ]

It’s unfortunate that more divers in the U.S. didn’t try a Y valve when they were available as they may be rather common today if they had given them a chance. There were a few things going against the Y valve when they were available here. First, they looked odd and most folks don’t like change. They gravitate to what they know and that is probably the same issue Scubapro is having with their current D420. Great regulator but it looks different so some divers are avoiding it.

Second, not only was the Y valve more expensive, it requires the use of another first stage that many could not justify when they could simply run two second stages from their current single setup. Where the Y valve really shines is in the increased safety/redundancy for diving with a single cylinder. Yes, doubles are an option but for non-deco dives at recreational depths, they are less than ideal.

As I have mentioned before, all of my single-cylinder dives are done utilizing a Y valve. I also sling a 40cf cylinder on all dives so If I switch to doubles (only used for deeper deco/mixed gas dives) the 40cf is switched out for 100% O2 rather than the same mix I am running in my single cylinder and pony which is usually 28%.

The Y valve offers two independent valves in one. Similar to a manifold with an isolation valve but instead of isolating a cylinder, you are just isolating a valve. If anything goes wrong with your primary first/second, you switch to the secondary and shut the primary valve down. These Y valves are even made with independent dip tubes so if by chance one gets obstructed, you have the other.

I run a transmitter off my primary post and a SPG off of the secondary post. I run two Perdix computers (one as a primary computer and one as a bottom timer) and this Y valve setup has worked great over the years. While it does look a bit odd, I am more likely to get other divers asking me if I have extras to sell over giving me funny looks about the setup.

 

[John C. Ratliff]

Okay, I've not read all this thread, but will tell you that I'm an older diver (will turn 77 next week), who dives mostly rivers and lakes in Oregon, USA. I don't overdo the redundancy aspect of diving, and have been diving these rivers and lakes since I started diving in 1959. I do take my cameras underwater and get photos of the aquatic life.

I ususally dive a single tank, sometimes older double hose regulators or part of my collection of single hose regulators. I don't overdo redundancy, since the surface is immediately available. I do usually have an octopus second stage, unless I'm diving totally vintage with a double hose regulator that doesn't incorporate that type of redundancy. I have a set of double tanks with a twin-post manifold that allows older double hose regulators along with a single hose regulator for my power inflator, SPG/Computer, etc. and an octopus or redundant second stage.

I find that diving in freshwater rivers in current that more redundancy is not necessarily good, as in current that adds resistance to the water's current. I sometimes dive in heavy current, sometimes under rapids. Here's a video I made a few years back of one of my dives in the Clackamas River. I also usually dive solo.


SeaRat

 

[mdwalter]

This forum provides so much useful information, it's incredible. But I couldn't find anything in regards to different setups for recreational diving. I'm not sure if the question is stupid Let's try. This will be a lot of text from my side and I'm wondering how experienced divers would rate the different setups.

My scuba background:

• I'm an AOWD with about 60 dives - most of them the typical holiday/tropical dives. I did and like more advanced dives such as diving in currents, night dives, entries of a cavern (no caves). Though I enjoy diving in the "deeper" region for rec divers (let's say 20-30 meters), this is not something I pursue to dive deeper, just to be deeper as anytime before. I like taking some pictures or videos of the dives, so I usually have some additional equipment with me.

General intention:

• I want to dive (more or less) full year in local rivers and lakes. Water temperatures varies from 4°C to >20°C, of which May - October (including) are above 10°C. Only January and February are below 5°C. I have no intention to dive at those temperatures.
• Pure recreational diving. I have no intention to do extra deco stops, use mixed gases, go below 40 meters, dive into narrow caves, or start using rebreathers. I do think that all of that is spectacular and would do that in another life but diving should be fun and easy for me. This does not mean I don't want to use technical stuff for diving - in fact I love technical stuff and I'm willing to invest training, money and time just to use the technics, though not at the limit. It's like to have a decent sports car: You can accelerate and brake faster than the others and the cornering speed is higher - but you don't have to drive at the limit to have fun (i.e. 1 km/h faster and you crash). Yes, waste of money for the potential of the car, but still so much fun.
• I don't have any issues with back, knees etc., I'm tall and strong, so moving dive equipment around, regardless the configuration, is very easy.
• Safety is priority number 1. Only diving with a buddy (or in a small group), never single.

Questions:

• I wonder which are the opinions of experienced divers which setup would be "best" or which have negative sides which could be eliminated with an "upgrade":
  • Single tank.Let's say 12 liter tank. 2x valves, 2x 1st stages etc.
    • Most simple set up. If free flow occurs, closing the primary valve should give enough air to either ascend normally or maybe use a little bit of buddy's air while ascending (depending how fast the valve is closed and how much air is left in the cylinder).
    • Dives will usually be limited by air supply, not by NDL.
  • Double tank. Let's say 2x8.5 liters or 2x10 liters. 2x valves, extra valve in between (manifold), 2x 1st stages etc.
    • More "advanced" setup. May give more dive time.
    • I'm not sure if this setup will increase safety at a free flow compared to a single tank? What could happen that this configuration is superior, i.e. the extra valve between the tanks?
      If I close (let's say) the right valve, is just the exit to the 1st stage blocked but air from the right cylinder can go to the left first stage? Or is the whole right tank shut off?
  • Sidemount. Let's say 2x7 liters or 2x 8.5 liters.
    • Most "technical" setup. May give that little "extra" to diving by just using it, though not really necessary. It's like using a dedicated espresso machine + milk frother instead of a fully automatic coffee machine. The espresso machine will give the same espresso/cappuccino, but the subjective taste is superior :-D
    • This setup should result in increased safety at a free flow: Just use the other regulator. Even if the easy-to-reach valve of the affected tank is not closed - the other should provide enough air to safely reach the surface.

I think the real questions come down to:
Is a double tank configuration in any case better than a single tank configuration for rec diving?
Or will the only question be: Go single tank or sidemount. A single tank is as safe as a double tank (my assumption) but sidemount adds the technical side and improves safety.

Looking forward to your opinions and any downsides/benefits I did not mention in above text

I would recommend something with some redundancy, so as not to have to rely on your buddy in case of a single failure in your life support system. That means either BM doubles or SM with 2 or more tanks. For recreational diving, I prefer either small BM doubles or small SM tanks (like LP 45s or 50s - or whatever that may be in metric). This allows for the same or slightly more volume of gas (at the same pressure) as a single tank diver with the ubiquitous AL80 or the popular HP100, HP120, etc. (whatever that may be in metric), but with the added safety of isolation of half your gas, 2 first stages, 2 second stages, and better balance and trim in the water with lower drag. The one tank I still have for single tank BM diving is fitted with a Y valve for the same reasons, but I almost never use it.
I consider SM the safest, due to the easier access and visibility of the tank valves, and more efficient due to the tanks being closer to the body and out of the flow. Doubles (small ones) are your next best option, with single BM dead last on both fronts. BM doubles win on simplicity of donning and doffing with thick suit and gloves because there is less to clip and unclip than SM, while SM wins in warmer water due to the ease of clipping tanks on and off without having to remove the whole harness and weight system.

 

[grf88]

It’s unfortunate that more divers in the U.S. didn’t try a Y valve when they were available as they may be rather common today if they had given them a chance. There were a few things going against the Y valve when they were available here. First, they looked odd and most folks don’t like change. They gravitate to what they know and that is probably the same issue Scubapro is having with their current D420. Great regulator but it looks different so some divers are avoiding it.

Second, not only was the Y valve more expensive, it requires the use of another first stage that many could not justify when they could simply run two second stages from their current single setup. Where the Y valve really shines is in the increased safety/redundancy for diving with a single cylinder. Yes, doubles are an option but for non-deco dives at recreational depths, they are less than ideal.
View attachment 757285

As I have mentioned before, all of my single-cylinder dives are done utilizing a Y valve. I also sling a 40cf cylinder on all dives so If I switch to doubles (only used for deeper deco/mixed gas dives) the 40cf is switched out for 100% O2 rather than the same mix I am running in my single cylinder and pony which is usually 28%.

The Y valve offers two independent valves in one. Similar to a manifold with an isolation valve but instead of isolating a cylinder, you are just isolating a valve. If anything goes wrong with your primary first/second, you switch to the secondary and shut the primary valve down. These Y valves are even made with independent dip tubes so if by chance one gets obstructed, you have the other.
View attachment 757286
I run a transmitter off my primary post and a SPG off of the secondary post. I run two Perdix computers (one as a primary computer and one as a bottom timer) and this Y valve setup has worked great over the years. While it does look a bit odd, I am more likely to get other divers asking me if I have extras to sell over giving me funny looks about the setup.

An H-Valve, that is readily available in North America, offers many of the same benefits of the Y-valve although the second valve is a little harder to access and manipulate than that on a Y-valve. It also does not provide for a second dip tube which really is not a big issue because if you are using one the chances are that they are on your own tanks which hopefully you maintain properly. The other issue is that it is easy for the H-portion to get rolled on during transit so it is a good idea to use a plug on that side if transported laying down.

 

[NW Dive Dawg]

I'm reminded of one incident with Adventures With a Purpose, where Jared (the lead) sent Doug (a relatively new diver) down to 100ft for the first time, with a bunch of new equipment including a FFM and a pony-bottle. Doug ran out of air, and ended up bolting to the surface. The pony bottle did him little good, because in his unfamiliarity, lack of training, and practice Doug wasn't ready to remove the FFM and switch to the pony.

Whatever config OP decides to pursue, he should obviously practice with at minimum. Personally, I switch to my backup regulator (octo, pony, SM, etc) at least once every dive for practice, to verify it's working, and properly secured in the right place. Training is obviously useful, but I think one could gain a benefit even without specific training, afterall, most of us learned regulator switching in Open Water.

In my opinion, the problem here is not the pony, as long as it was fully charged and good to go. The HUGE problem is both Doug and Jared's poor decision choosing the FFM with no additional planning, practice , training or planning for emergency contingencies.

The BIGGEST problem of course was that the guy ran out of air. That just can't happen.

Other than maybe adjusting your weighting a bit, using a fully charged back mounted Pony requires no substantial additional training and using it is every bit as simple as would be a basic switch from a primary 2nd stage to a normal alt (octo). My 19 pony is firmly back mounted and the 2nd stage lives in a normal oct holder on my starboard chest area. My actual safe second for alternate access to my main tank or a share gas scenario is a Scuba-Pro Air II on my BC inflator.. I also keep a smaller 2in SPG tethered to my pony 2nd stage so that I can easily check pressure before and most importantly for me.....during......my dive. I know that this overall configuration is not popular to a lot of folks here but it's what has worked for me for years and most importantly what I am used to, practiced with. I dive primarily solo or end up solo after getting separated on hunting / gathering dives....

 

[SlugLife]

In my opinion, the problem here is not the pony, as long as it was fully charged and good to go. The HUGE problem is both Doug and Jared's poor decision choosing the FFM with no additional planning, practice , training or planning for emergency contingencies.

The BIGGEST problem of course was that the guy ran out of air. That just can't happen.

Other than maybe adjusting your weighting a bit, using a fully charged back mounted Pony requires no substantial additional training and using it is every bit as simple as would be a basic switch from a primary 2nd stage to a normal alt (octo). My 19 pony is firmly back mounted and the 2nd stage lives in a normal oct holder on my starboard chest area. My actual safe second for alternate access to my main tank or a share gas scenario is a Scuba-Pro Air II on my BC inflator.. I also keep a smaller 2in SPG tethered to my pony 2nd stage so that I can easily check pressure before and most importantly for me.....during......my dive. I know that this overall configuration is not popular to a lot of folks here but it's what has worked for me for years and most importantly what I am used to, practiced with. I dive primarily solo or end up solo after getting separated on hunting / gathering dives....

I agree with pretty much everything you said.

the problem here is not the pony

In my opinion, Doug lied about the incident, and he never tried to switch to the pony. What good is redundant air if you don't use it in an emergency? It's not the pony's fault, but rather on the user-end.

The HUGE problem is both Doug and Jared's poor decision choosing the FFM with no additional planning, practice , training or planning for emergency contingencies.

Precisely. Almost nothing about the dive was complex, even for a beginner. It was all these little things you listed (and more) all at the same time. A little bit of practice with each piece of equipment, or each new thing, 1-at-a-time would have been better.

The BIGGEST problem of course was that the guy ran out of air.

"The car skidded out of control!" If you rewind the clock, we find a distracted texting driver, neglected brakes, bald tires, and more. Any one of those is a hazard on it's own, but we basically have someone playing Russian-roulette with 3 bullets in the gun.

By the time he ran out of air, it was somewhat predictable.

 

[Tracy]

Personally I've never experienced that. This last summer I was diving in the great lakes from a boat using SM, no problems and no questions asked. In september I dove SM for a week in Cozumel, again no problems. In both cases I did call ahead to make sure it was ok.

You are correct, but it was mentioned. I know which boat and where you were.

Sidemount on a boat is a crap shoot. The reasons captains hate it is because 99.7% of sidemount divers are horrible at it. Tuning a sidemount setup for a boat is completely different than setting it up for a cave. You may be great once you are in the water, but there are additional steps involved with doing it on a boat.
It CAN work, I have seen it work.
But honestly, of the 100s of people that I have seen try it, I can think of 2 that were good at it and did it well enough to be seamless gearing up with backmount divers.

 

[SlugLife]

You are correct, but it was mentioned. I know which boat and where you were.

Sidemount on a boat is a crap shoot. The reasons captains hate it is because 99.7% of sidemount divers are horrible at it. Tuning a sidemount setup for a boat is completely different than setting it up for a cave. You may be great once you are in the water, but there are additional steps involved with doing it on a boat.
It CAN work, I have seen it work.
But honestly, of the 100s of people that I have seen try it, I can think of 2 that were good at it and did it well enough to be seamless gearing up with backmount divers.

Why is SM the boat captain's problem?

 

[grantctobin]

Why is SM the boat captain's problem?

Because it’s his/her boat and he’s responsible for it and the people on it?

It’s not often as seamless as SM divers suggest that it is

 

[L13]

You are correct, but it was mentioned. I know which boat and where you were.

Sidemount on a boat is a crap shoot. The reasons captains hate it is because 99.7% of sidemount divers are horrible at it. Tuning a sidemount setup for a boat is completely different than setting it up for a cave. You may be great once you are in the water, but there are additional steps involved with doing it on a boat.
It CAN work, I have seen it work.
But honestly, of the 100s of people that I have seen try it, I can think of 2 that were good at it and did it well enough to be seamless gearing up with backmount divers.

I am far from being the best SM diver from a boat or the shore. However, in both cases I mentioned, I was good enough that there were backmount divers that were less "seamless." In both cases, when I called ahead, the operators seemed happy to take my business and there was no grumbling I notice while I was on the boat. The biggest issue seemed to be ensuring there were tanks with DIN valves available.

I do think the courtesy of calling ahead made a difference. And, I would not be upset at an operation for saying no since in a group of sufficiently experienced backmount divers I would have stood out and been a pain to everyone, crew and divers alike.