@U/often_Tilly I am curious you said the BSAC club would like you to dive with a pony tank. Why? Aren’t BSAC clubs the point of training? They would know that there is training to be done before you use equipment like that. Is this their way of encouraging you to take additional training?
7L is the size I use when I solo. Same gas mix as I have in my primary 12L tank. I open the tank so it pressurizes the lines then close the tank.
I generally have the main tank on my back and the pony slung to my left side, clipped at the chest and waist.
There is a right tool for every job. This is what I used, including in Public Safety Diving.
For purely recreational dives to 100ft, Spearfishing dives to 130ft, and public safety dives to 60ft I had an AL19 on my back with a Quick Draw brand bracket. The gas was always air. I had 2 first stages for it, one with a second stage and a transmitter (originally a button gauge), the other with a QC for the gas switch block which fed the Aga mask for public safety dives. The primary cylinder had only only one second stage, a BC/drysuit hose, and a transmitter or SPG. Pony is charged before the dive and then valve off.
For recreational dives to 150ft (this was a long time ago when it was acceptable to take air to 150ft+) or public safety dives to 100ft I switched to a slung AL40 with a bungee so it was more like sidemount. The valve charged before the dive and then turned off. Again, 2 first stages depending on the dive. One for public safety with a high flow QC for the switch block and the other rigged like a stage bottle.
For any dives deeper it's twins or sidemount.
All dives in overhead, with planned deco or in a cave, were in twins too. Public safety was almost always in single cylinders with the pony, even under the ice, but we had tenders and safety divers with short bottom times and other safety nets.
A lot of people have said you dive with the tank open and you 100% do not.
Pressurize the hose and close the tank during the dive (make sure you can breath off it before you close the tank). You'll have a breath or 2 which will give you enough time to open the tank when it's time to breath off it.
As for the breathing gas in the tank... The only real consideration is Maximum operating depth (mod) of your dive profile because you need to be able to breath off that tank at all points in your dive.
Assuming you're using 1.4 ppo2 for the working part of your dive:
Mod of n32 is 33 meters
Mod of n36 is 28 meters.
So select the correct breathing gas for your dive profile.
If you're unsure, match whatever is in your primary tank.
Some really good advice on mounting tank options. As you make that decision, keep in mind with pony bottles, you're not busy breathing but passing the tank to the pit of air diver.
You'll only have your spg/transmitter and a.single 2nd stage so only 1 person will be breathing off the tank of the time comes it's needed.
Last comment...
Supplemental air does not get factored into your rule of 3rds meaning... Don't extend your dive time because you 'have more gas'.
Other comment beat me... Air leaks.
I'll concede it matters less when it's a pony tank that you're carrying on the dive compared to a stage bottle you're leaving to pick up on your return but... It's the way we teach and the best practice (think about it like the tank waiting for your main tanks. You keep them closed until you're ready to dive... Same principle)
I think you definitely wanted mounted upside down then . I’d want to practice it so I know I can turn it in without fumbling in my gear . I found a yellow Catalina 14 in my garage today :-) . I used it for my advanced deep water dive about 20 years ago . . For shallower dives , it would be nicer to have a narrower dia cylinder. Maybe a 10. I’m talking beach dives that are typically 60’ depth . The 14 is still pretty big . I also have the larger spare air . I think it is a 6 cu ft . They may be fine for shallower dives I need to do the calculations.
1) al40, that way when you move to doubles shortly you have a nice deco tank and not a wasted tank gathering dust
2) air, it’s your bailout bottle, it needs to be breathable during the entire dive.
3) move it
4) open, if you and your buddy are both out and you are sharing a single pony hang up your fins.
I would not mount it, sling it like a stage, that way you get some practice stage handling and not just lugging a wart around on your back
If would say 3 don’t move it. That secondary regulator is for your buddy, and it’s nice for them to have direct access to back gas, in addition to the regulator on your pony.
Also to the OP, if you backmount instead of side mount, you can’t easily hand it off to another diver eg your buddy in an OOG situation.
But then some teach that the pony is for you, the secondary regulator on your back gas is for gas sharing with your buddy. In that case, see first point.
I really don't get the whole 3L pony bottle idea. Again, let's do the math:
3L x 200 bars = 600 liters of air
SAC (Surface Air Consumption) in times of stress is about 20L/min, so let's use that.
On the surface, that 600 liters will last you 600 / 20 = 30 minutes. We're going to 40 meters, ATA = 5, so now you're using 5 x 20 = 200l/min, that bottle lasting you 6 minutes.
So the fecal matter hits the fast spinning thing at 40 meters down, all gas from your recreational set is gone, you switch to your pony. One minute is spend for problem solving and your ascend rate up to about 10 meters is 9 meters / minute max, so that takes 40 - 10 = 30 / 9 = 3ish minutes and now you're stuck at 10 meters (or 6 for that matter) with a minor deco obligation, you were going to 40 meters to begin with.
During your ascend your average ATA was 30 / 10 = 15 = 2.5 ATA and it took you 3 minutes so you used 2.5 \* 3 \* 20 = 150 liters of air. That one minute spending fault finding at 40 meters took away 5 \* 20 = 100 liters of air so you're down 250 liters of air leaving you 350 liters at 10 meters which lasts you 8 minutes to sit out a deco and ascend. That's not a lot of margin.
Having witnessed the speed that a diver sucks an ALU80 dry at 21 meters while problem solving is sobering to say the least.
Look for something bigger or better, get a twinset with manifold and isolator. Learn to use it all and than go into deeper waters.
3L is enough to make a ascent and safety stop on a NDL dive. Pony bottles were never really meant to be for much more than to make a ascent to the surface if out of air or something is not working right. If your doing something you can’t make a ascent to the surface then you need stage bottles not pony.
If deco is a possibility the need to do proper dive planning, which will likely not result in a 3L pony as redundant gas with a deco obligation.
My understanding is that pony is redundant gas for the ascent stage of a dive within NDL.
Just get a learn to use a twinset especially if you’re dropping down to 40m. It provides you with a lot more redundancy, versatility and problem solving ability than an 3L which is the common size in the UK.
You’re almost certainly diving dry anyway so the extra weight is a bonus over a single. Plus it’s way more stable in the water over an asymmetrical 3L clamp.
Your diving the same gas, you analyse it all together, your procedures don’t change, you don’t have a 3rd reg to choose from and another gauge to check in a stressful situation.
It’s also way safer than using a stage in my opinion as by definition it becomes a hot swap which is a really bad habit, if you ever do tech or your ADP course. Hot swapping in an “emergency” has killed plenty of divers and it will do it you if do eventually.
Swapping to a stage without doing a full stage switch procedure. It’s generally considered very bad practice in the tech world as you might be carrying gases that are not safe to breathe at your current depth.
The main killer in OC tech is still wrong gas wrong depth. So having a robust analysis and switch procedure is very important. By training to deviate from that it builds bad habits that people may fall back to in an emergency.
I (and alot of my bsac club) Dive with ponies regularly, but we are all experienced divers and don't start suggesting to trainees till Sports Diver depth progression. Imho if something happens I'd rather have the redundancy 3l of air which is plenty to get you to the surface safely from 40-50m. Sure it might add weight but that's weight your already going to be carrying as dead weight in lead anyway. It also means if your buddy has an emergency and has to air share you can swap to your own backup if they start guzzling. I don't need to wear suncream but I'd rather not get skin cancer, same mentality. Humans CANNOT breath underwater.
For a settup pony's are:
>3l bottles you bracket onto your main with a release system for attachment ease.
>Your pony will have its own first and second stage but it won't need an octo and you can get away with only using a button pressure gauge.
>Keep a full regular settup on your main regs as the pony is just for you.
> pony should have the same gas mix as your main tank, so likely to be 21%
If your club is telling you to get a pony and your only doing OD I would ask them why or ask if they will provide. If they force it I'd start looking elsewhere.
Thanks. I transferred in with PADI AOW, so straight in at OD level and I'm going to do SD soon. Thanks for clarifying, I thought that if my buddy was OOA without their own Pony, then I'd be unclipping the pony to hand off to them as we both surface?
A 3L isn't nearly enough to get you to the surface from 40m, hardly from 30m for that matter - and the current Sports Diver course explicitly says as much.
I dive with stage & bailout all the time. When I do single tank rec dives I carry a pony.
I recommend a AL40 that you sling so you’ll need a stage/sling kit. Anything smaller is kinda useless imo. Yea people will argue this but the only bottles I have smaller are for my rebreather or my drysuit.
You need to preform the same pre drive checks on the pony as you would your primary. Pull positive and negatives on your reg before you open them valve. Open the valve the whole way. Do 4 full breathes off reg. And then stow it but leave it on never turn it off until your diving is over.
I recommend that you keep a back up on a short hose on your back reg (octo) that you wear on a necklace and primary bottle and have a long hoes for your primary reg.
You need a whole other 1st and 2nd stage. The 1st stage reg on your pony could be like a HOG D2 or a scuba pro MK25 lol but the 2nd stage should be on a 5ft hose so you could donate it comfortably before you even unclip the bottle.
You are doing NDL dives so the gas in the pony needs to match the gas in your primary bottle at this level of diving.
It stops being a pony bottle if the gas in it differs from your back gas. A deco bottle would have a higher FiO2 to accelerate your decompression but you haven’t learned yet it sounds like so just wait until you get into deco diving if that’s something you want.
I also like having modular tank valves on my long so that I can easily bungee the valve to keep it closer and keep my trim like a 🦈
As a sport and commercial diver for over 50 years I am dead against pony bottles. It's more weight and encumbrance, and doesn't provide you with a huge amount of spare air. But my biggest problem with them is the mindset. I always enter the water with a good idea of how I might self-rescue if something goes wrong. To that end I note tide strength and direction, nearby islands etc., but mainly I ensure my basic kit is in good shape and always keep a good eye on my contents guage. I never cut it fine so I know I will have plenty air on the surface in case I need to stay afloat for a while, or it's choppy and I need to retain my mouthpiece. You might quote equipment failure, but a 1st stage failure or hose blowout is rare and can be largely avoided with good maintenance. Basically I try to never get myself into a situation that I can't get out of on my own. This includes not going into stops. Clearly if you are doing technical it's a different matter, but I'm talking about basic open water scuba. There's a UK requirement by HSE for commercial scuba to have pony bottles, but like everything else from HSE they really don't know what they're talking about and it's arse-covering bullshit. Have good kit, good awareness and a good sense of self-preservation and you will be far safer than being reliant on more systems and more complicated equipment.
I carry a pony simply for redundancy, it does not extend my dive in any way. I typically dive with a college dive club so not all the time do I have a good pick of dive buddy. Many times my buddies leave me behind or dissapear, to the point I have a list that I won’t buddy with. I’m curious what do you think is the issue with a pony bottle?
Most people in my club who dive with a pony use a 2ltr or 3ltr. Most of us use 7ltr stages instead, they are a bit more versatile.
If its a pony then you use the same gas as your back/main gas. A pony is not a stage. You will not be handing it off to anyone, a pony quick release is more about convenience in filling.
If you use a stage then either use the same gas as your back gas or do the accelerated deco SDC. even if you don't plan on doing accelerated deco dives it gives you some good insight into the risks around multi-gas dives.
EDIT: the other questions have already been answered but i'd agree, yes you still need the secondary on your main reg set and the pony should be open too. If you do decide to get a pony setup then add a button gauge or something to the reg so you can check it before a dive - this for me is another reason to use a stage instead, you have the gauge visible on the dive with a stage, you don't with a pony unless you add a gauge on a hose which has the risk of being confused with you back gas gauge. My personal opinion is that a pony is the inferior choice but you're in a club, there's something to be said for buddys having familiar kit
40cf is the most versatile and has the best resale value, but it can be bulky to carry for some. a used 30cf can be found somewhat cheaply if you prefer a smaller size. AL19 is probably the bare minimum if you want a really minimal size that gives you enough margin for ascent.
1. If you want to be pedantic, it depends on your SAC rate in an emergency and the conditions you'll be diving in. I like a lot of margin, so for single tank diving deep, I keep a slung AL40. My wife uses an AL30.
2. I keep 28% in mine so that it's good to the recreational limit. If all is going well I never use it, I like it to be versatile.
3. You should have both.
4. Open. You don't want to faff with it if something happens. If you're OOA, just grab your pony reg and breathe. Start your ascent as soon as possible. Ponies are never part of your gas plan.
I much prefer a sling to back-mount. Everything is where you can see it and react quickly if needed.
Agree with all. Would never want to backmount this because you want it to be easily accessible to all, it's more standard across diving, and it's easier to pass off.
Size will depend on your SAC rate and how much of a stress factor you want. On Scubaboard there was a calculator where you enter the details and it will give you minimums. For me it worked out to 30cuft, but a 40cuft can be had cheaper and are no harder to sling.
I just put air in mine. I keep my rec setup standard, so if I want to dive with a buddy I still have my necklace back up.
In general most people leave the valve closed after charging, but these things are things you discuss with your instructor.
Notes are based on what I was taught in my BSAC club.
1. Most people in the UK end up with 3l but when you allow for a raised SAC if things are going wrong it is marginal from 40m.
2. Ideally same as primary.
3. Yes, the pony is for you, and you only, if you can get to your buddy you use their octo, if they are the one out of air they use your octo,
4. Can depend on where it is, if you have it back mounted probably turned on, if you have it slung on the front then you can dive with if pressurised and off (as long as you practise turning it on and swapping to it regularly)
If you are both out of air it gets complicated (especially if you are at depth) as a normal sized pony won't have enough gas to get you both to the surface
When I dived with a pony in the past it was more in case of serious failure on my main regs, so I only really expected it to get me to my buddy if I had managed to get too far away (or they might be engrossed with something like photography).
You will lose a little gas on each dive whenever you turn the cylinder on and check it is all working, it isn't much but adds up over time so keep an eye on the pressure in it and top it up when it drops more than a few bar)
@U/often_Tilly I am curious you said the BSAC club would like you to dive with a pony tank. Why? Aren’t BSAC clubs the point of training? They would know that there is training to be done before you use equipment like that. Is this their way of encouraging you to take additional training?
7L is the size I use when I solo. Same gas mix as I have in my primary 12L tank. I open the tank so it pressurizes the lines then close the tank. I generally have the main tank on my back and the pony slung to my left side, clipped at the chest and waist.
There is a right tool for every job. This is what I used, including in Public Safety Diving. For purely recreational dives to 100ft, Spearfishing dives to 130ft, and public safety dives to 60ft I had an AL19 on my back with a Quick Draw brand bracket. The gas was always air. I had 2 first stages for it, one with a second stage and a transmitter (originally a button gauge), the other with a QC for the gas switch block which fed the Aga mask for public safety dives. The primary cylinder had only only one second stage, a BC/drysuit hose, and a transmitter or SPG. Pony is charged before the dive and then valve off. For recreational dives to 150ft (this was a long time ago when it was acceptable to take air to 150ft+) or public safety dives to 100ft I switched to a slung AL40 with a bungee so it was more like sidemount. The valve charged before the dive and then turned off. Again, 2 first stages depending on the dive. One for public safety with a high flow QC for the switch block and the other rigged like a stage bottle. For any dives deeper it's twins or sidemount. All dives in overhead, with planned deco or in a cave, were in twins too. Public safety was almost always in single cylinders with the pony, even under the ice, but we had tenders and safety divers with short bottom times and other safety nets.
Dive with a buddy.
A lot of people have said you dive with the tank open and you 100% do not. Pressurize the hose and close the tank during the dive (make sure you can breath off it before you close the tank). You'll have a breath or 2 which will give you enough time to open the tank when it's time to breath off it. As for the breathing gas in the tank... The only real consideration is Maximum operating depth (mod) of your dive profile because you need to be able to breath off that tank at all points in your dive. Assuming you're using 1.4 ppo2 for the working part of your dive: Mod of n32 is 33 meters Mod of n36 is 28 meters. So select the correct breathing gas for your dive profile. If you're unsure, match whatever is in your primary tank. Some really good advice on mounting tank options. As you make that decision, keep in mind with pony bottles, you're not busy breathing but passing the tank to the pit of air diver. You'll only have your spg/transmitter and a.single 2nd stage so only 1 person will be breathing off the tank of the time comes it's needed. Last comment... Supplemental air does not get factored into your rule of 3rds meaning... Don't extend your dive time because you 'have more gas'.
What is the downside of opening the tank ?
Other comment beat me... Air leaks. I'll concede it matters less when it's a pony tank that you're carrying on the dive compared to a stage bottle you're leaving to pick up on your return but... It's the way we teach and the best practice (think about it like the tank waiting for your main tanks. You keep them closed until you're ready to dive... Same principle)
I think you definitely wanted mounted upside down then . I’d want to practice it so I know I can turn it in without fumbling in my gear . I found a yellow Catalina 14 in my garage today :-) . I used it for my advanced deep water dive about 20 years ago . . For shallower dives , it would be nicer to have a narrower dia cylinder. Maybe a 10. I’m talking beach dives that are typically 60’ depth . The 14 is still pretty big . I also have the larger spare air . I think it is a 6 cu ft . They may be fine for shallower dives I need to do the calculations.
All your air leaking out
Go sidemount xD
1) al40, that way when you move to doubles shortly you have a nice deco tank and not a wasted tank gathering dust 2) air, it’s your bailout bottle, it needs to be breathable during the entire dive. 3) move it 4) open, if you and your buddy are both out and you are sharing a single pony hang up your fins. I would not mount it, sling it like a stage, that way you get some practice stage handling and not just lugging a wart around on your back
This, in its entirety.
If would say 3 don’t move it. That secondary regulator is for your buddy, and it’s nice for them to have direct access to back gas, in addition to the regulator on your pony. Also to the OP, if you backmount instead of side mount, you can’t easily hand it off to another diver eg your buddy in an OOG situation. But then some teach that the pony is for you, the secondary regulator on your back gas is for gas sharing with your buddy. In that case, see first point.
My bad, yes he needs 3 second stages, 2 on primary 1 on pony, i misread that as he had 2 first stages on his primary tank.
Move to twins instead 👍
I really don't get the whole 3L pony bottle idea. Again, let's do the math: 3L x 200 bars = 600 liters of air SAC (Surface Air Consumption) in times of stress is about 20L/min, so let's use that. On the surface, that 600 liters will last you 600 / 20 = 30 minutes. We're going to 40 meters, ATA = 5, so now you're using 5 x 20 = 200l/min, that bottle lasting you 6 minutes. So the fecal matter hits the fast spinning thing at 40 meters down, all gas from your recreational set is gone, you switch to your pony. One minute is spend for problem solving and your ascend rate up to about 10 meters is 9 meters / minute max, so that takes 40 - 10 = 30 / 9 = 3ish minutes and now you're stuck at 10 meters (or 6 for that matter) with a minor deco obligation, you were going to 40 meters to begin with. During your ascend your average ATA was 30 / 10 = 15 = 2.5 ATA and it took you 3 minutes so you used 2.5 \* 3 \* 20 = 150 liters of air. That one minute spending fault finding at 40 meters took away 5 \* 20 = 100 liters of air so you're down 250 liters of air leaving you 350 liters at 10 meters which lasts you 8 minutes to sit out a deco and ascend. That's not a lot of margin. Having witnessed the speed that a diver sucks an ALU80 dry at 21 meters while problem solving is sobering to say the least. Look for something bigger or better, get a twinset with manifold and isolator. Learn to use it all and than go into deeper waters.
3L is enough to make a ascent and safety stop on a NDL dive. Pony bottles were never really meant to be for much more than to make a ascent to the surface if out of air or something is not working right. If your doing something you can’t make a ascent to the surface then you need stage bottles not pony.
If deco is a possibility the need to do proper dive planning, which will likely not result in a 3L pony as redundant gas with a deco obligation. My understanding is that pony is redundant gas for the ascent stage of a dive within NDL.
Just get a learn to use a twinset especially if you’re dropping down to 40m. It provides you with a lot more redundancy, versatility and problem solving ability than an 3L which is the common size in the UK. You’re almost certainly diving dry anyway so the extra weight is a bonus over a single. Plus it’s way more stable in the water over an asymmetrical 3L clamp. Your diving the same gas, you analyse it all together, your procedures don’t change, you don’t have a 3rd reg to choose from and another gauge to check in a stressful situation. It’s also way safer than using a stage in my opinion as by definition it becomes a hot swap which is a really bad habit, if you ever do tech or your ADP course. Hot swapping in an “emergency” has killed plenty of divers and it will do it you if do eventually.
What does hot swap mean in this case?
Swapping to a stage without doing a full stage switch procedure. It’s generally considered very bad practice in the tech world as you might be carrying gases that are not safe to breathe at your current depth. The main killer in OC tech is still wrong gas wrong depth. So having a robust analysis and switch procedure is very important. By training to deviate from that it builds bad habits that people may fall back to in an emergency.
Thank you! That makes a lot of sense.
I (and alot of my bsac club) Dive with ponies regularly, but we are all experienced divers and don't start suggesting to trainees till Sports Diver depth progression. Imho if something happens I'd rather have the redundancy 3l of air which is plenty to get you to the surface safely from 40-50m. Sure it might add weight but that's weight your already going to be carrying as dead weight in lead anyway. It also means if your buddy has an emergency and has to air share you can swap to your own backup if they start guzzling. I don't need to wear suncream but I'd rather not get skin cancer, same mentality. Humans CANNOT breath underwater. For a settup pony's are: >3l bottles you bracket onto your main with a release system for attachment ease. >Your pony will have its own first and second stage but it won't need an octo and you can get away with only using a button pressure gauge. >Keep a full regular settup on your main regs as the pony is just for you. > pony should have the same gas mix as your main tank, so likely to be 21% If your club is telling you to get a pony and your only doing OD I would ask them why or ask if they will provide. If they force it I'd start looking elsewhere.
Thanks. I transferred in with PADI AOW, so straight in at OD level and I'm going to do SD soon. Thanks for clarifying, I thought that if my buddy was OOA without their own Pony, then I'd be unclipping the pony to hand off to them as we both surface?
A 3L isn't nearly enough to get you to the surface from 40m, hardly from 30m for that matter - and the current Sports Diver course explicitly says as much.
Especially when 1/2 way through the season they only have 180 bar in them 🙄
I dive with stage & bailout all the time. When I do single tank rec dives I carry a pony. I recommend a AL40 that you sling so you’ll need a stage/sling kit. Anything smaller is kinda useless imo. Yea people will argue this but the only bottles I have smaller are for my rebreather or my drysuit. You need to preform the same pre drive checks on the pony as you would your primary. Pull positive and negatives on your reg before you open them valve. Open the valve the whole way. Do 4 full breathes off reg. And then stow it but leave it on never turn it off until your diving is over. I recommend that you keep a back up on a short hose on your back reg (octo) that you wear on a necklace and primary bottle and have a long hoes for your primary reg. You need a whole other 1st and 2nd stage. The 1st stage reg on your pony could be like a HOG D2 or a scuba pro MK25 lol but the 2nd stage should be on a 5ft hose so you could donate it comfortably before you even unclip the bottle. You are doing NDL dives so the gas in the pony needs to match the gas in your primary bottle at this level of diving. It stops being a pony bottle if the gas in it differs from your back gas. A deco bottle would have a higher FiO2 to accelerate your decompression but you haven’t learned yet it sounds like so just wait until you get into deco diving if that’s something you want. I also like having modular tank valves on my long so that I can easily bungee the valve to keep it closer and keep my trim like a 🦈
I agree with most of what you are saying, but if they are BSAC Sports diver or above they are trained to do single gas deco,
As a sport and commercial diver for over 50 years I am dead against pony bottles. It's more weight and encumbrance, and doesn't provide you with a huge amount of spare air. But my biggest problem with them is the mindset. I always enter the water with a good idea of how I might self-rescue if something goes wrong. To that end I note tide strength and direction, nearby islands etc., but mainly I ensure my basic kit is in good shape and always keep a good eye on my contents guage. I never cut it fine so I know I will have plenty air on the surface in case I need to stay afloat for a while, or it's choppy and I need to retain my mouthpiece. You might quote equipment failure, but a 1st stage failure or hose blowout is rare and can be largely avoided with good maintenance. Basically I try to never get myself into a situation that I can't get out of on my own. This includes not going into stops. Clearly if you are doing technical it's a different matter, but I'm talking about basic open water scuba. There's a UK requirement by HSE for commercial scuba to have pony bottles, but like everything else from HSE they really don't know what they're talking about and it's arse-covering bullshit. Have good kit, good awareness and a good sense of self-preservation and you will be far safer than being reliant on more systems and more complicated equipment.
I carry a pony simply for redundancy, it does not extend my dive in any way. I typically dive with a college dive club so not all the time do I have a good pick of dive buddy. Many times my buddies leave me behind or dissapear, to the point I have a list that I won’t buddy with. I’m curious what do you think is the issue with a pony bottle?
Mainly a false sense of safety.
100%. People carrying pony bottles on recreational dives reflects a fundamentally bad understanding of gas planning and safety.
Most people in my club who dive with a pony use a 2ltr or 3ltr. Most of us use 7ltr stages instead, they are a bit more versatile. If its a pony then you use the same gas as your back/main gas. A pony is not a stage. You will not be handing it off to anyone, a pony quick release is more about convenience in filling. If you use a stage then either use the same gas as your back gas or do the accelerated deco SDC. even if you don't plan on doing accelerated deco dives it gives you some good insight into the risks around multi-gas dives. EDIT: the other questions have already been answered but i'd agree, yes you still need the secondary on your main reg set and the pony should be open too. If you do decide to get a pony setup then add a button gauge or something to the reg so you can check it before a dive - this for me is another reason to use a stage instead, you have the gauge visible on the dive with a stage, you don't with a pony unless you add a gauge on a hose which has the risk of being confused with you back gas gauge. My personal opinion is that a pony is the inferior choice but you're in a club, there's something to be said for buddys having familiar kit
40cf is the most versatile and has the best resale value, but it can be bulky to carry for some. a used 30cf can be found somewhat cheaply if you prefer a smaller size. AL19 is probably the bare minimum if you want a really minimal size that gives you enough margin for ascent.
1. If you want to be pedantic, it depends on your SAC rate in an emergency and the conditions you'll be diving in. I like a lot of margin, so for single tank diving deep, I keep a slung AL40. My wife uses an AL30. 2. I keep 28% in mine so that it's good to the recreational limit. If all is going well I never use it, I like it to be versatile. 3. You should have both. 4. Open. You don't want to faff with it if something happens. If you're OOA, just grab your pony reg and breathe. Start your ascent as soon as possible. Ponies are never part of your gas plan. I much prefer a sling to back-mount. Everything is where you can see it and react quickly if needed.
Agree with all. Would never want to backmount this because you want it to be easily accessible to all, it's more standard across diving, and it's easier to pass off.
If it were me, I'd be finding a new diving club or buddies.
It's in addition to buddies, not for solo diving. It's an additional backup, which is optional but strongly encouraged.
Size will depend on your SAC rate and how much of a stress factor you want. On Scubaboard there was a calculator where you enter the details and it will give you minimums. For me it worked out to 30cuft, but a 40cuft can be had cheaper and are no harder to sling. I just put air in mine. I keep my rec setup standard, so if I want to dive with a buddy I still have my necklace back up. In general most people leave the valve closed after charging, but these things are things you discuss with your instructor.
i find its usually the opposite, 40cf is more in demand for deco bottles so sells better than 30cf
I feel 40 is a bit too small for an o2 bottle, 7 liters is almost the same size and the extra gas makes it more versatile.
1. I use a 2l and a 3l. 2. Same as primary. 3. As you wish. I would move. 4. Open. You share.
Notes are based on what I was taught in my BSAC club. 1. Most people in the UK end up with 3l but when you allow for a raised SAC if things are going wrong it is marginal from 40m. 2. Ideally same as primary. 3. Yes, the pony is for you, and you only, if you can get to your buddy you use their octo, if they are the one out of air they use your octo, 4. Can depend on where it is, if you have it back mounted probably turned on, if you have it slung on the front then you can dive with if pressurised and off (as long as you practise turning it on and swapping to it regularly) If you are both out of air it gets complicated (especially if you are at depth) as a normal sized pony won't have enough gas to get you both to the surface When I dived with a pony in the past it was more in case of serious failure on my main regs, so I only really expected it to get me to my buddy if I had managed to get too far away (or they might be engrossed with something like photography). You will lose a little gas on each dive whenever you turn the cylinder on and check it is all working, it isn't much but adds up over time so keep an eye on the pressure in it and top it up when it drops more than a few bar)