How To Carry A Pony Bottle When Diving Doubles

Defining "Personal Distance Limit"

Your navigational skills notwithstanding, there is one last thing to consider with regard to safe exits and that is factoring into your dive plans, your personal distance limit.

Personal distance limit is the distance from a safe exit point that you can surface swim without physical over exertion. It is somewhat variable and may be used to gauge how far you can swim from a dive's exit point at depth before it's time to turn around and head back. It's a useful measurement to have when working on contingency plans, and can tell a diver that in the event of an emergency ascent where she surfaces far from her safe exit, she has the stamina to make it back on the surface in full gear.

One way to calculate a baseline for personal distance limit is to don full gear and swim laps of set distance parallel to the shore line in moderate sea conditions. Your personal distance limit is the point at which you start to feel slight fatigue.When planning your dives, it's common to set a distance to a turn-around point that is no greater than 40 percent of your limit.

Review Questions

1. What is the essential first step in staying on route during a dive?

2. Name five typical waypoints on a wreck dive.

3. What is a good distance to use to work out a diver's kick / breathe cycles?

4. What is meant by a reciprocal reading in basic navigation?

5. What are compass variation and deviation?

Special Equipment for Solo Diving

In this chapter, you'll learn about:

What Equipment a Solo Diver needs Different types of redundant air sources Other Mandatory Equipment Equipment configuration Understanding Your Equipment

There is very little about the equipment a solo diver uses that is so different to the usual gear one would expect to find on someone diving with a buddy. The only slight differences in what you'd see are there to offer some level of redundancy or back-up since the solo diver does not have her buddy's equipment or help to fall back on.

What Equipment a Solo Diver Needs

A properly equipped diver will wear the following.

• Cylinder (fully charged)

• Buoyancy Compensator

(suitable for the environment and the types of dives being done)

• Primary regulator (serviced at least annually)

• Redundant regulator / Octopus (serviced annually)

• Dive computer (standard fare for all SDI divers) ° Compass (worn either on wrist or in console)

• Pressure Gauge (serviced and calibrated regularly)

• Cutting device

(worn on hip, shoulder or someplace readily accessible)

• Some sort of Thermal protection

(Dry Suit, Semi-Dry Suit or Wet Suit in most areas

• Mask (well fitting, and inspected for wear and tear regularly)

• Fins (comfortable and easy to doff and don)

• Weight (either integrated or on a weight belt)

• Rescue Signal (surface marker, whistle, Dive Alert ™)

A properly equipped Solo diver will carry the same equipment with only one major modification and a few small additions. Let's look at that major modification first.

Different Types of Redundant Air Sources

In the transition from a buddy diver to a solo diver, we have discussed in every previous chapter how we need to change our attitude, planning, awareness, now we need to think about what piece of gear we'd miss in an out of air emergency diving alone: That's correct. Our buddy's octopus. This alone remains one of the biggest arguments in favour of the buddy system and has helped codify the buddy system's advantages in the general diving community; however, an independent diver can achieve a similar level of security by adding a completely independent cylinder and regulator system to their dive kit in any number of ways. The options include:

Fitting a single cylinder with a H or Y valve, carrying a pony bottle filled with suitable backgas, using Dual Cylinders with an isolation valve manifold, carrying a Spare Air.

Having a completely redundant gas system is a fundamental rule in solo diving and a diver attempting a solo dive without backup gas supply fitted with a redundant first and second stage regulator is courting disaster.

H and Y valves and Double Cylinders

One of the real-world situations that can cause a massive gas hemorrhage is a regulator first-stage problem - perhaps a freeze-up and run-away free-flow or maybe a high-pressure seat giving up the ghost. One way a diver can manage this risk is to have a "back-up" or redundant regulator that he can switch to before shutting down the offending primary reg.

With a single cylinder we can achieve this functionality in two ways: an H or Y valve. This option has two independent regulators connected to the same cylinder and allows a diver to turn off the offending regulator in the event of a free flow. Frankly, many SDI divers prefer this type of valve on their cylinder for dives below 30 metres /100 feet, even when diving with a buddy.

This solution is perhaps the least complicated for a solo diver. H or Y valves are inexpensive and simple to fit and will offer an acceptable degree of redundancy in many sport diving situations.

However, this is an inadequate solution in the event of burst-disk failure or an extruded O-ring event with a single tank. In these cases, even though both are rare occurrences, all gas would be lost in minutes and a diver's exit would need to be very rapid... not the best situation.

Another option is to use a set of twinned tanks with an isolation manifold. This tank configuration is gaining popularity and is the standard among open circuit technical divers. Closing the isolator has the singular advantage of turning the twinned cylinders into two completely independent gas systems in the event of a burst disk or extruded neck o-ring event.

This option too has its disadvantages. It is heavy, expensive, takes sometime to become proficient with in the water, is overkill for recreational sport diving, requires an additional investment for backplate and wings (BC and harness), and requires a slightly more complex method of gas planning since until that isolation valve is closed, gas is drawn down from both cylinders and if one does not pay attention to dropping gas volumes, by the time dive three of the day rolls around, may hold an insufficient volume of back-up gas to completely cover one's retreat in the event of an emergency. Of course, there are advantages too. The system is self-contained, it is the standard if you wish to move on to recreational technical diving, and once one is used to diving with doubles, one seldom goes back to single cylinders.

Rig Pony Bottle
Typical doubles rig showing two first stages.


Air is available to both regulators from both cylinders.


The isolator is closed. Air on right goes to the right regulator and air on the left goes to the left regulator.

The post on the right is closed but the gas from the right cylinder is available to the left regulator.


Air is available to both regulators from both cylinders.


The isolator is closed. Air on right goes to the right regulator and air on the left goes to the left regulator.


The post on the right is closed but the gas from the right cylinder is available to the left regulator.

Pony Bottle

In SDI's opinion - and this is something you may wish to discuss with your instructor and other experienced divers because all input is valid - the best solution for the single tank diver is the use of a separate small volume pony bottle (sometimes referred to as a stage or sling bottle). This typically is a compact aluminum cylinder complete with regulator and small SPG. Since a pony bottle or stage cylinder is a totally separate, independent life-support system it manages well the risks associated with catastrophic loss of primary gas source.

The pony bottle's volume will depend largely on the underwater excursion being planned, but in the example we've used in this chapter where the reserve gas held for emergencies was 1100 litres or about 40 cubic feet and it would be logical to use either an aluminium 6 litre or 40 cubic foot cylinder FULLY CHARGED since this would mean that even after a catastrophic gas failure with our primary gas system, we can switch to the stage cylinder and return home at "normal" speed from any point in the dive!

Three vitally important things about a Stage cylinder:

1. The gas it contains should NEVER be included in the available gas calculations! The reason for this is it is suppose to be only used in a complete gas loss of your primary system. Depending on it as a primary gas, even if for safety margin, is never a good idea.

2. The gas in it should have the same MOD as one's regular back gas. The reason for this is in order for the diver to be able to safely breathe the gas at any depth during the dive; the mix in the cylinder must be the same in order to avoid DCI

or Oxygen Toxicity.

3. The whole system should be check for func tionality and visually inspected for wear and tear before every dive and should be deployed to check in water operations on every dive (during the safety stop for instance). Due to the fact the stage cylinder would only be used in an emergency and emergencies are rare, divers often get complacent about checking their safety equipment. But in the case of a stage cylinder, if it is not working or not completely filled when the diver needs it, then it is no good to them at all.

How to Carry a Stage

One popular and functional way to carry a stage cylinder is to have it slung at one's side much the same way as technical diver's carry stage bottles for decompression gases. The advantages of this method include accessibility and ease of removal. Also the regulator can be stowed neatly near the valve or worn attached to a "necklace" around the diver's neck. In addition the SPG can be on a small hose out of the way and completely discrete, but visible to the diver.

The other way to carry a stage cylinder is to attach it to the side of your primary cylinder on your back. The advantage to this method is it out of the way from interfering with your hands and arms if you happen to be carrying a camera or something else. Along with the standard way you would normally store an octopus regulator, is the same way you would store your redundant second stage that is attached to your stage cylinder.

It is important to note that the solo diver does not need any other type of redundant regulator like an Octopus or Air2. The reason is if there was ever a problem, the solo diver would just go to their back up system. By having an Octopus or Air2, the solo diver has two problems they normally would not need to deal with if they didn't have those pieces of equipment: An unnecessary failure point and extra drag from the equipment they don't need.

Other Mandatory Equipment

The additional equipment required for the solo diver is a surface marker buoy (SMB), a reel, and a surface audible signalling device.

Surface Marker Buoy's

More commonly known as an SMB, this piece of equipment is used to signal the boat of your location. Typically they are brightly colored either red or yellow and when fully inflated stand at least 2 metres / 7 feet out of the water.


Arguably the one "extra" piece of equipment every diver should carry no matter if they are solo diving or not, it has many uses. The most common use is to attach the line to the SMB while underwater and "shoot" the bag to the surface, prior to the diver surfacing, as a way of making the dive boat or other boats aware of your location prior to surfacing.

The reel can also be used in water with very poor visibility as a way of maintaining the diver's orientation while underwater. For instance, say the solo diver was diving from a charter boat on a wreck. The visibility in the water was less than 2 metres / 7 feet. The solo diver would need to descend to the wreck following the anchor line down. When the diver reached the wreck, how would they be able to find the ascent line back to the boat in such poor visibility? The answer is simply! By attaching the reel to the anchor line or a place very close to the anchor line, the diver could simply swim away from the anchor line while letting their reel unwind. When they wanted to return, they would simply reel up the line they had let out and follow it back to the anchor line.

Surface Audible Signalling Device

There are many different types of signalling devices on the market today, but the most common is a whistle. The reason for carrying a whistle is bring attention to the location of the diver when they surface if they should surface away from the charter boat. This is another example of a piece of equipment all divers should carry.

Some Optional Pieces

Some solo divers also like to carry dye marks, signal mirrors, flares, or Emergency Position Indicating Radio Beacons (EPIRB's). All of these are used in the case of being pulled out to sea or missing a boat back to shore. Each of these needs to be carried in a dry pressure resistant container so they do not get wet at depth. The best one is of course the most expensive, the EPIRB. A common piece of safety equipment on every charter boat, it wasn't until very recently that divers started caring them with them on dives. The EPIRB is by far the best locating device available to a lost diver, because they way it works is when it is activated, it sends out a signal that can easily be picked up by any search and rescue team like the Coast Guard. It will bring the Search team directly to the location of the diver and in the case of the ocean; a solo diver would be very hard to spot on their own.

The others like the signal mirror, flares or dye rely on the diver being in close location to the search team, because they are visual signals that are used to bring attention the area the solo diver is locate.

The draw of redundant equipment is a bit of a siren call for some divers and there is a tendency to jump into the water looking like a cross between a Christmas tree and a wall display at dive store. We need to carry some extras if diving alone but we have to be selective when planning what those extras are.

Whether diving alone or with a team of buddies, SDI recommends carrying a back-up mask and practicing deploying it on most dives. A back-up bottom timer and depth gauge or a backup computer is also essential for a solo excursion. SDI is also a firm believer in cutting devices and carrying a small knife on your waist, a pair of shears with Wetnotes, and a third Zknife on the handle of a light. If not using a light, the third cutting device is a second small knife near the left shoulder. Wearing knives on the calf area are more difficult to reach than a pocket on the waist strap of the harness. When you are thinking about where to wear your cutting tools, find spots you can reach easily and with either hand.

Equipment Configuration

One of the most hotly debated topics of all experienced divers is how they configure their equipment. However there are 3 issues all experienced divers will agree to when talking about configuration.

1. Is it streamlined?

3. Does the diver fully understand how their configuration works?

1. Streamlined

By now you must have seen at least one diver that looks like their equipment is more of a hindrance underwater rather than an extension of themselves. The reason for streamlining your equipment is to be sure that you can minimize the amount of drag the equipment causes. Remember as a solo diver, you have to be able to get yourself back, so the easier you can make that process, the better.

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Guide To Scuba Diving

Guide To Scuba Diving

Many people think that space is our final frontier and that is not entirely true. While it is more difficult to get to outer space, we probably know more about the various planetsand environments in space than wedo about what lies beneath the surface of our oceans.

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  • dinodas
    How to carry a pony bottle when diving doubles?
    4 years ago
  • efrem
    What i should consider buying a pony bottle for solo diving?
    4 years ago
  • Kristian
    Is it nessary to carry a pony bottle while usin a ffm?
    3 years ago
  • marvin
    What is the best way to carry a pony bottel?
    2 years ago
  • JUHA
    How do you attach a pony bottle to a set of doubles for seperate air source?
    1 year ago
  • wanda
    Who carries a pony bottle while diving?
    12 months ago
  • angelica grubb
    How to wear a pony bottle?
    6 months ago

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