What's your pony setup?

[johndiver999]

I took a minute to read the accounts and I agree with @saxman242, the incidents were related to training rather than indicating that a back mounted pony if inherently dangerous. In the first case a diver did not properly check that his air was on, this could happen with a back mount single or back mount doubles too. In the 2nd incident a diver did not know which regulator was which. That he did an arm sweep to recover a lost regulator and ended up with the regulator attached to his pony rather than his primary tells me it is likely that his backup was dangling freely rather than being properly secured. Then the diver, when OOA, never switched to the other tank, that sounds like a training issue not a configuration issue to me.

There are practices, and equipment configurations,that you can use to minimize the risk, but not fully eliminate it. For example on my back mounted pony my primary is a 40’ hose wrapped under arm and my back mounted pony is on a short hose that is bungled around my neck (in primary donate fashion). This works well and is one of the techniques mentioned in the thread you referenced.

I tend to think the OP in that thread drew the wrong conclusions. The conclusions he should have drawn were that pre-dive checks need to be thorough and divers should be highly familiar with their configurations and trained to do the dives they engage in. Specifically the OP in that thread concluded that side slung ponies are safer than backmount ponies because tech diver have been using them that way for decades. He attributes success to the wrong thing, configuration vs training.

I would also say that Scuba diving is inherently dangerous, that is why training is required before you are allowed to dive and you have to routinely practice skills to maintain proficiency.

Back mount or slung configurations both add safety factors that are not available if the redundant system is not carried.

You are correct that those deaths should not have occurred if the divers did not make mistakes. However, training (and even practice) is not 100% insurance that people will not still make mistakes.. Training just reduces the chances of the mistake being made. However in addition to training, some gear configurations are going to reduce the chance for human errors.

A back mounted pony is thought to be more convenient by many people - compared to a slung bottle. Whether that assumption/conclusion is correct or applicable is probably a matter of opinion and may be situational dependent upon what activities the diver is engaged in underwater.

A back mounted pony has a negative aspect in that it provides an additional location to snag lines, fishing line etc. This conclusion is a fact, not an opinion. Whether that is important or not is a matter of opinion.

Many back mounted pony bottles are rigged without an spg that can be viewed during the dive. This is presumably done for convenience and simplicity and it does eliminate a potential failure point. However, it is a fact that not having real time data on the pressure in the pony immediately before and during an emergency is "less safe" than knowing that info. Of course a back mounted pony can be rigged with a long spg hose or even a transmitter I assume.

A slung pony bottle does have a significant safety advantage in that the user can always see how much pressure is in it. The user can also more easily monitor the unit for leaks during the dive.

The slung pony also has the significant advantage that if the second stage were to screw up and start freeflowing, the bottle MAY still be usable by manually feathering the bottle on and off for each inhalation cycle on the ascent. These seem to be safety factors or attributes that increase safety or robustness of the system. I don't think you can argue effectively to the contrary. You may be able to argue that these particular benefits of a slung bottle are minuscule or irrelevant in a recreational setting, but that is a personal opinion.

Another drawback to a back mounted pony is associated with the failure of the valve, first stage, hoses or o-rings. If a failure occurs here during a dive, it may not be obvious to the solo diver which of the two tanks has experienced a failure. There are procedures or tasks that could be implemented to diagnose and distinguish which tank (pony or primary) has the problem, but this is clearly more task loading during a potential emergency. This weakness is a fact and is entirely avoided by using a slung pony where it should take less than one second to determine if the leak or blown hose is in front of you or behind your neck.

Of course, the second stage from the slung pony is almost 100% impossible to be confused with a second stage from the primary tank and this feature would have presumably prevented some deaths.

If a diver back mounts a pony upside down, SOME of these weaknesses are reduced or eliminated.. but not all.

Based on all these issues, I think it is logical to conclude that a slung pony is safer than a back mounted one. I don't see how these issues can be interpreted in any other manner.

However, it is up to the diver to decide how to mount the pony. Does perceived convenience trump SOME safety/robustness aspects of the slung pony? That is a subjective decision, and I would not criticize a diver for back mounting a pony bottle if that was their decision.

Our goal is to have fun, if it were to eliminate all possible risks, we definitely wouldn't be diving.

 

[saxman242]

When I explored backmounting mine, I was looking at mounting it to the backplate like a drysuit argon bottle (using a 13 cu ft tank) rather than way back on the tank. That gave better access to the valve for turning on/off or feathering and makes for a big reduction in entanglement issues. One could easily mount an spg for viewing the tank contents, and having it upside down, in that position, makes it really easy to tell where leaking air is coming from. I felt that going that route pretty much took care of any of the safety concerns you're talking about.

I still opted to sling because it's just so much easier and convenient, but if I was spearfishing, etc, I might reconsider.

 

[loosenit2]

Back mount or slung configurations both add safety factors that are not available if the redundant system is not carried.

You are correct that those deaths should not have occurred if the divers did not make mistakes. However, training (and even practice) is not 100% insurance that people will not still make mistakes.. Training just reduces the chances of the mistake being made. However in addition to training, some gear configurations are going to reduce the chance for human errors.

Agree completely

A back mounted pony has a negative aspect in that it provides an additional location to snag lines, fishing line etc. This conclusion is a fact, not an opinion. Whether that is important or not is a matter of opinion.

Perhaps, but no more risk than back mounted doubles, which i dive as well.

Many back mounted pony bottles are rigged without an spg that can be viewed during the dive. This is presumably done for convenience and simplicity and it does eliminate a potential failure point. However, it is a fact that not having real time data on the pressure in the pony immediately before and during an emergency is "less safe" than knowing that info. Of course a back mounted pony can be rigged with a long spg hose or even a transmitter I assume.

A slung pony bottle does have a significant safety advantage in that the user can always see how much pressure is in it. The user can also more easily monitor the unit for leaks during the dive.

I used double transmitters, one on my main and one on the pony for real time monitoring. A a minimum you should have a button gauge on your pony to ensure starting pressure. If during a dive you have to switch to your pony your dive is over, you should begin an immediate safe ascent, just like if you have to share air with another diver.

The slung pony also has the significant advantage that if the second stage were to screw up and start freeflowing, the bottle MAY still be usable by manually feathering the bottle on and off for each inhalation cycle on the ascent. These seem to be safety factors or attributes that increase safety or robustness of the system. I don't think you can argue effectively to the contrary. You may be able to argue that these particular benefits of a slung bottle are minuscule or irrelevant in a recreational setting, but that is a personal opinion.

Another drawback to a back mounted pony is associated with the failure of the valve, first stage, hoses or o-rings. If a failure occurs here during a dive, it may not be obvious to the solo diver which of the two tanks has experienced a failure. There are procedures or tasks that could be implemented to diagnose and distinguish which tank (pony or primary) has the problem, but this is clearly more task loading during a potential emergency. This weakness is a fact and is entirely avoided by using a slung pony where it should take less than one second to determine if the leak or blown hose is in front of you or behind your neck.

This is the same risk you have with doubles. The answer is that you should position your back mounted pony in such a way that you can reach the valve to turn it on or off, same with your primary gas supply. Identifying which one was a problem is a simple matter of running an S-Drill (minus the isolation valve of course) (Disclosure, this was not always the case for me, I was coached into it, benefit of SB).

Of course, the second stage from the slung pony is almost 100% impossible to be confused with a second stage from the primary tank and this feature would have presumably prevented some deaths.

If a diver back mounts a pony upside down, SOME of these weaknesses are reduced or eliminated.. but not all.

Based on all these issues, I think it is logical to conclude that a slung pony is safer than a back mounted one. I don't see how these issues can be interpreted in any other manner.

However, it is up to the diver to decide how to mount the pony. Does perceived convenience trump SOME safety/robustness aspects of the slung pony? That is a subjective decision, and I would not criticize a diver for back mounting a pony bottle if that was their decision.

Our goal is to have fun, if it were to eliminate all possible risks, we definitely wouldn't be diving.

You bring up good points, many of them I agree with. I tend to believe you should dive the configuration you are trained in and most comfortable with. My main point was not to argue FOR back-mounting a pony, but rather than back-mounting a pony is not inherently dangerous.

 

[wetb4igetinthewater]

@TDiddy this thread has a good spreadsheet that @wetb4igetinthewater did last year for calculating what size pony you may need.

Spreadsheet for helping pick a pony bottle

Just realized that I didn't have that file here: Kosta's Dive Documents - Google Drive

It is there now.

 

[johndiver999]

Diving IS inherently dangerous. A slung pony is safer than back mount.

 

[lowviz]

Everyone has to decide what works best for them. Except for a Spare Air. That's always wrong.

No, No! No, it isn't.

Years ago, my old tech LDS told me of a HazMat trucker who came in to buy a dive mask and the biggest Spare Air that he could get. If anything happened he was going to don the mask, stick the SA in his mouth and RUN LIKE HELL!

And that is a quote.

 

[saxman242]

No, No! No, it isn't.

Years ago, my old tech LDS told me of a HazMat trucker who came in to buy a dive mask and the biggest Spare Air that he could get. If anything happened he was going to don the mask, stick the SA in his mouth and RUN LIKE HELL!

And that is a quote.

When calculating your SAC rate for running from a hazmat spill, what stress factor should you use to determine cu ft needs? 5x?

 

[Gareth J]

No, No! No, it isn't.

Years ago, my old tech LDS told me of a HazMat trucker who came in to buy a dive mask and the biggest Spare Air that he could get. If anything happened he was going to don the mask, stick the SA in his mouth and RUN LIKE HELL!

And that is a quote.

I did some work on one of the Royal Ordnance Sites, part of the brief
"If you hear a continuous siren, run like **** to the nearest bunker....."

 

[TDiddy]

Your Solo class should have you calculating your RMV and basing the redundant supply on that. If it's not, I'd think about finding another instructor. You should know your SAC before you take the class and have the gear bought to handle your needs.

Great point - I decided to do my first SAC test last night.

 

[Fastmarc]

Divers spearfishing seem to favor tank mounted ponies.

Often thought this is when having it slung would be most beneficial. Un-clip it and shove it in the mouth of that charging shark.