Pull Dumps — lose them

[John Bantin]

People here seem to have lost sight of what a BC is for. Surely, the primary point of a Buoyancy Compensator is to compensate for the loss of buoyancy caused as the suit is reduced in volume due to the pressure of depth? Similarly, if you use a drysuit with a constant-volume valve, you need never use the BC apart from use as a surface support. Maybe if people went back to diving as we used to, without any buoyancy compensator, they might get the hang of proper weighting and realise how little lift they actually need. Orally injecting air into the corrugated hose of a Fenzy (ABLJ) would be the next step and you would realise how little air you need to do the job - if you are properly weighted to begin with.

 

[tarponchik]

I was once buddied with a guy who didn't have his Inflator hose connected. Obviously, I pointed this out during our buddy check. His response was that its deliberate. He said he was properly weighted, and at depth he would need at most 2 breaths to orally inflate his BCD to be neutral.

He had once had a power inflator malfunction and he wasn't ever going there again!

Happened to me once but it was easier to clean the valve than to change my habits. Power inflators are too handy.

 

[guyharrisonphoto]

I agree that lack of training in proper weighting is a huge bugaboo in modern instruction. I have gone to my LDS and gotten "empty" (500 psi or less) AL80s, Steel HP 100s and steel HP 120s and then, for each tank gone and weighted myself to hold a 20' safety stop (my preferred depth) with my wing empty. I have done this for my 3 and 5mm wetsuits. This took an hour or so at a shore dive spot. It was some of the best time i have spent. It dials in the weighting with no excess (although I go a pound or two "over" to account for any air that might be in the wing after an active dive, etc). I was, in fact, surprised at how little weight I needed. Dropped about six pounds from what I had been using.

Having done this, I can easily adjust weight for other tanks by getting their empty buoyancy off of the internet and adjusting my weighting accordingly. If I ever used a 7mil wetsuit, I would do the actual water test again.

 

[Soloist]

The BC wasn't a fix for overweighting, but it allowed instructors to cut short or skip the time needed to properly weight a diver.

I am often baffled when divers tell the crew how much weight they require for a single aluminum tank recreational dive. Huge numbers! I know, I know, everybody and every “body” is different. I also understand the impact poodle jackets, BPW, exposure protection and skill set can have on weight requirements, but I still can’t rationalize the numbers.

This always reminds me of my own naïveté as a new diver in 2009. My OW instructor discussed proper weighting as part of the curriculum, but it obviously had no impact on me. Fortunately we took AOW shortly thereafter. When I told my new instructor how much lead I required he very politely informed me that I was an imbecile. He immediately removed 6 pounds and continued to remove more weight as the week progressed. The difference was amazing.

There are a lot of competent, insightful and diligent instructors focused on producing capable and self aware divers, just read their posts on SB. However, some instructors simply teach the rudiments resulting in complacent divers. I have seen numerous divers ask the guide how much weight do they need. I hear “it’s better to have too much weight than not enough” on just about every dive trip. Although true, this mindset can be problematic. The importance of proper weighting and trim should be emphasized and drilled into the new diver during OW training. I’m sure this topic has been discussed many times over on SB, but this issue hits close to home.

 

[boulderjohn]

This always reminds me of my own naïveté as a new diver in 2009. My OW instructor discussed proper weighting as part of the curriculum, but it obviously had no impact on me. Fortunately we took AOW shortly thereafter. When I told my new instructor how much lead I required he very politely informed me that I was an imbecile. He immediately removed 6 pounds and continued to remove more weight as the week progressed. The difference was amazing.

Most OW instructors MUST overweight students to a significant degree so that they can stay firmly planted while kneeling on the bottom of the pool (and the OW bottom) while learning and demonstrating basic skills. the instructors must also be very much overweighted so that they can do kneeling demonstrations flawlessly. Instructors who instead teach students while they are neutrally buoyant (not kneeling) find that it is best to have them properly weighted. By far most instructors cling to the belief that kneeling is the best way to instruct, so their students leave class with a grossly exaggerated belief of what they need for weight.

I could relate many, many stories like yours.

 

[Soloist]

Most OW instructors MUST overweight students to a significant degree so that they can stay firmly planted while kneeling on the bottom of the pool (and the OW bottom) while learning and demonstrating basic skills.

Makes perfect sense. This is the exact scenario we experienced. Performing our required skills kneeling on a platform at 15 feet in a quarry. We purchased all new gear immediately AFTER being certified, so even if we would have worked on proper weighting and trim it would have been with a hodgepodge of gear. But it still would have been an informative exercise.

 

[rongoodman]

People here seem to have lost sight of what a BC is for. Surely, the primary point of a Buoyancy Compensator is to compensate for the loss of buoyancy caused as the suit is reduced in volume due to the pressure of depth?

And the weight of the gas used during the dive, which these days can be substantially more than that contained in the smaller cylinders of old.

 

[Celt]

To heavy getting in the water, if there was no air in the bcd he still should not have sunk from the surface.

 

[gcarter]

My first 100 or so were in a BCD with a pull dump. It was of no use to me - at least I never used it past my first dozen or so - because of the strain it places on the weld at the bladder and the risk of failure. I never replaced it with an elbow, I just never used it. The last 200+ have been with a wing with no pull dump.

I have never seen any value in the pull dump. When I first started diving I found it hard to control anyway. The valve at the end of the hose gave me better control.

 

[gcarter]

Taking a step back here looking @oldschoolto's point, what is a more common failure, stuck inflator or inadvertent shoulder dumping?

My money is on the stuck inflator, which has likely actually killed divers. It seems a shoulder dump is an excellent solution for a relatively common scuba problem.

It is equally as easy to press the other button on the inflator hose... the one that lets the air out. It still works when the inflator is stuck.