Should You Carry a Pony Bottle?

What’s a Pony Bottle—and Why Do Divers Use Them?

A pony bottle is a small, independent scuba cylinder that some divers carry as a backup air source. It’s typically equipped with its own regulator and carried slung under the arm or mounted to the main tank. Sizes vary, but common pony bottles range from 13 to 40 cubic feet.

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
13 cuft	6.5 min	4.3 min	Shallow dives, surface bailout only
19 cuft	9.5 min	6.3 min	Safer shallow dive backup
30 cuft	15 min	10 min	Moderate-depth bailout ascent
40 cuft	20 min	13.3 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 clipped off to a bolt snap
Neck strap or bungee to keep it streamlined
Secure bottom bolt snap to 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 (Coming Soon)

Final Thoughts

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.