Pony Bottle


A pony bottle is a compact diving cylinder equipped with an independent regulator, designed to serve as an auxiliary air source for scuba divers in the event of an emergency. This secondary air supply can be a lifesaver during situations where the diver’s primary air source is depleted or compromised. The term “pony” in the name refers to the bottle’s relatively small size compared to standard scuba cylinders. This entry will explore the purpose, features, and best practices for using a pony bottle while diving.


The primary purpose of a pony bottle is to provide an alternative air supply for divers in case their main air source fails or is unexpectedly depleted. By using a pony bottle, divers can safely ascend to the surface without having to rely on a buddy’s alternate air source, which might not always be available or accessible during a critical situation. Some divers also use pony bottles as a redundant air supply when diving in overhead environments like caves or wrecks, where direct access to the surface is restricted.

Capacity and Contents:

The capacity of a pony bottle varies depending on the specific needs of the diver and the planned dive profile. Typically, the cylinder’s size ranges from 13 to 40 cubic feet (0.4 to 1.1 cubic meters), with 19 cubic feet (0.5 cubic meters) being the most common size. The contents of the bottle should provide enough air for the diver to make a safe ascent from any point in the dive plan, factoring in decompression stops, if necessary. Most pony bottles are filled with compressed air, but in some cases, they may contain nitrox or trimix, depending on the diver’s preference and dive requirements.

Features and Attachments:

A pony bottle has several features that distinguish it from a standard scuba cylinder. These include:

  1. Independent Regulator: The pony bottle is equipped with its own regulator, allowing the diver to breathe directly from the cylinder without connecting to their primary air source.
  2. Mounting System: Pony bottles can be attached to the diver’s primary cylinder using various mounting systems, such as brackets, straps, or clips. This ensures that the bottle remains secure and accessible throughout the dive.
  3. Pressure Gauge: A pressure gauge is often included with the pony bottle to provide the diver with an accurate reading of the remaining air supply.
  4. Overpressure Relief Valve: Like standard scuba cylinders, pony bottles also have an overpressure relief valve to prevent the risk of cylinder rupture due to excessive internal pressure.

Best Practices for Using a Pony Bottle:

Divers should follow a few best practices when using a pony bottle to ensure its effectiveness and safety:

  1. Familiarity: It is essential for divers to familiarize themselves with their pony bottle and its regulator, as they may need to use it in high-stress situations. This includes regularly practicing switching to the pony bottle during training dives.
  2. Pre-dive Checks: Before each dive, divers should check the pony bottle’s pressure to ensure it has enough air for a safe ascent. They should also inspect the regulator and mounting system for any signs of damage or wear.
  3. Periodic Maintenance: Like all scuba equipment, pony bottles and their regulators require periodic maintenance to ensure proper function. Divers should follow the manufacturer’s recommendations for servicing and inspection intervals.
  4. Streamlining: When mounting a pony bottle, it is crucial to minimize drag by positioning the cylinder close to the diver’s body and securing it tightly. This can improve the diver’s hydrodynamics and reduce the risk of entanglement.

In conclusion, a pony bottle is an essential piece of safety equipment for divers seeking an independent alternative air source. By understanding its purpose, features, and best practices, divers can maximize the benefits of using a pony bottle and enhance their overall diving safety. When properly selected, maintained, and utilized, a pony bottle can provide invaluable peace of mind and a critical backup in emergency situations. It is important for divers to choose a pony bottle that suits their specific needs and planned dive profiles and to practice using it regularly to ensure a smooth transition in case of an emergency. By integrating a pony bottle into their diving equipment, divers can be better prepared to handle unforeseen challenges, further promoting a safer and more enjoyable underwater experience.