The idea is simple: if something goes wrong and your main gas supply is no longer working, you switch to your pony bottle and safely ascend. Sounds smart, right? Maybe. But let’s break it down.
Why Do Some Divers Use Pony Bottles?
Here’s why some recreational divers carry pony bottles:
- Out-of-air redundancy: You don’t trust your buddy to share gas in an emergency or you might not have a buddy at all.
- Solo diving: You’re diving alone, against agency guidance, and need a backup.
- Cold water or deep diving: Freeflows or failures are more likely, and the stakes are higher.
- Peace of mind: It just feels safer to have your own backup air.
All of these are understandable concerns. But that doesn’t mean a pony bottle is the best solution.
Limitations and Trade-Offs
Before you strap on extra gear, think through the downsides:
- Extra weight and drag
- More hoses, more failure points
- Requires training to deploy safely under stress
- Easily misconfigured (e.g., valves off, second stage not secured)
- False sense of security you may start diving beyond your actual limits
Worse, pony bottles are often used as a band-aid for poor planning or bad buddy systems. That’s not safe, it just hides the real problem.
Should You Carry One?
Let’s look at some common scenarios:
| Situation | Pony Bottle Needed? |
|---|---|
| Solo diving | Yes. But also reconsider diving solo |
| Poor buddy skills | Maybe. But fixing the buddy problem is better |
| Cold/deep dives with freeflow risk | Possibly. But make sure your gas matches your depth |
| Nervous diver wanting backup | Consider proper training or a larger main tank first |
If you’re thinking about a pony bottle, ask yourself:
What failure am I actually trying to protect against and is this the best solution?
Pony Bottle Size Comparison (RMV 1.0 cuft/min)
Let’s run the numbers.
We’ll assume:
- RMV = 1.0 cuft/min because you are going to be a little excited
- Ascent rate = 10 ft/min
- No deco, just a direct ascent from depth
- Pony bottle is filled to full rated capacity
| Pony Size | Run Time at 60 ft | Run Time at 100 ft | Likely Use |
|---|---|---|---|
| 3 cuft (SpareAir) | 1 min | ~10 breaths | Totally useless |
| 6 cuft (SpareAir) | 2 min | 1 min | Totally useless |
| 13 cuft | 4 min | 3 min | Shallow dives, surface bailout only |
| 19 cuft | 6 min | 4 min | Safer shallow dive backup |
| 30 cuft | 10 min | 7 min | Moderate-depth bailout ascent |
| 40 cuft | 14 min | 9 min | Conservative backup for most rec dives |
Important: This table does not account for Minimum Reserve Gas, stress response, or buddy emergencies. For real gas planning, see our Recreational Gas Planning Guide.
Mounting and Configuration Options
If you do choose to carry a pony bottle, how you configure it matters because an unusable backup is worse than no backup at all.
Here are the most common mounting methods, along with pros and cons:
| Method | Description | Pros | Cons |
|---|---|---|---|
| Slung (Stage Style) |
Carried clipped to chest and hip D-rings like a stage or deco bottle |
- Easy to donate or hand off - Valve visible and accessible - Mimics proper tech configuration |
- Requires training - Slightly more drag - Can snag if not cleanly routed |
| Back-mounted to Main Tank |
Mounted to side of primary tank |
- Streamlined - Always with you |
- Hard to reach valve - Can’t confirm pressure - Not donatable |
| Back-mounted upside down |
Mounted inverted at base of primary tank |
- Streamlined - Always with you - Could be useful for someone with shoulder injuries |
- Requires training as the action is totally abnormal - Can’t confirm pressure - Not donatable |
Best Practice: Sling It
If you’re going to carry a pony, the safest, most accessible option is to sling it like a stage bottle:
- Valve facing forward and visible
- Second stage secured to the pony with a quick release something, not a boltsnap
- Secure top bolt snap to left chest D-ring
- Secure bottom bolt snap to left hip D-ring
This lets you see, reach, and deploy it under stress and it mimics proper bailout configuration for technical diving, which makes it easier to transition if you go that route later.
Avoid back-mounted setups unless you’ve trained specifically to reach and use them with drysuit/glove bulk. I will never rely on a configuration where I can’t confirm gas pressure, valve position, and second stage function underwater.
My Setup
I personally carry a side-slung 40 cuft bottle filled with air when I plan dives near 100 ft in cold water, like Lake Michigan wreck dives. It gives me a clean bailout option and redundancy in case of a regulator freeflow or other failure. I also bring it along on shallower dives just for practice, so deploying and managing it becomes second nature.
Better Alternatives
You might not need a pony bottle at all. In most cases, these are better options:
- Train with reliable dive buddies who understand gas sharing
- Use proper gas planning with a minimum reserve (not just “come up at 700 PSI”)
- Carry a long hose + backup second stage so you can donate cleanly
- Upgrade your main tank (AL80s are often too small for real redundancy)
- Get training in team protocols like those taught in GUE Fundamentals
Pony bottles are one way to add redundancy, but they aren’t the best way for most recreational divers. If you’re diving within your limits, with a competent buddy, and planning your gas properly, you probably don’t need one.
If you’re pushing limits, diving solo, or in overhead environments, a pony might be the bare minimum and even then, there are better tools (like proper bailouts and team protocols).
Solve the root problem. Don’t patch it with a pony.