Bear in mind these key hints from MARTIN SAMPSON, whose experience extends right back to the days of the ABLJ. He also took the photos
When I first learned to dive, we didn’t have buoyancy compensators. We started training with a simple backpack and cylinder. It was pot luck whether or not your diving cylinder buoyancy would match your own natural buoyancy.
In my case, being small and slim, it never did so. I spent weeks demonstrating competence at bunny-hopping around the floor of the swimming pool before finally being allowed to progress to bunny- hopping in open water. Eventually I was introduced to an advanced piece of equipment that carried the warning: “This Device Can Kill”.
This was the Adjustable Buoyancy Life Jacket (ABLJ), and it had an emergency inflation diving tank so that you could shoot to the surface in contravention of most strategic arms limitation treaties. Hence that warning: If you didn’t suffer an air embolism during the ascent, a Russian MIG fighter would shoot you down shortly afterwards.
You wore an ABLJ over your wetsuit before donning your cylinder. With the crotch-strap too tight, inflating the jacket made it capable of being both a pain in the neck and a pain in the arse simultaneously. It was impossible to ignore the fact that you were wearing one, because it got in the way of everything.
On one occasion I got dragged over the side of an inflatable while playing the part of a casualty, only for the entire direct-feed assembly to get snagged in a rope handle and ripped from the front of the ABLJ.
At the end of a normal dive you took your cylinder off in the water and passed it up onto the boat, much as you do now, except that the cylinder wasn’t assisted by a buoyancy device. Several rigs ended up on the seabed after enthusiastic deck-crew answered “Yes!” to the question “Have you got it?”, when in actual fact they meant “No!”.
We called this a life jacket but it wasn't, because it couldn’t be guaranteed to float us face-up at the surface if we were incapable of operating it.
As we grew more enlightened, we started to inflate the ABLJ routinely under water and – gasp – we experienced the holy grail of neutral cylinder buoyancy. Until the day the direct-feed failed, in which case we either went back to bunny-hopping or the opposite, ballistic ascents.
The emergency cylinder needed to be tested every couple of years as well, so a lot of ABLJs also got checked every two years. These days, for every 10 regulators that come in for service, I might get one BC – and even then only because it already has a problem.
Unlike the ABLJ, modern BCs with a scuba tank spend far too much time attached to cylinders, where they can end up lying face-down in the sand, or having other diving tanks stacked on top of them on the deck of a boat. Of course, they are also still prone to the age-old problem of direct-feed buttons sticking, so how best to prolong the life of your BC.
Remember these top tips
1. If your diving cylinder needs filling, take it along detached from the BC, so that the compressor operator doesn’t have to trip over harness-straps and stamp on the buckles.
Sand in dump-valve
2. This will surprise no one – wash your BC in fresh water after use. I service plenty of BCs that seem to have been cared for, yet they have corroded and faulty direct-feed units. I’m sure that you remember to drain the seawater out of your BC, but do you also drain it after you’ve rinsed it? I ask this because if you drain seawater out through the direct-feed, you will be storing a rinsed BC but with a direct-feed flooded with salt water.
Draining water through dump-valve instead of direct-feed
3. Inflate the BC and allow it to dry. This is a good opportunity to see if it stays inflated. Dump-valves can leak because of debris underneath the diaphragm. Most BC dump-valve assemblies simply unscrew, so as long as they’re not too tight or require special tools / procedures, it’s easy to remove them to clean out the rubbish. If the bladder itself leaks, you can pinpoint the leak by submerging the inflated BC. A small hole can sometimes be repaired with Aquasure or something similar, but this might not be possible if the hole is close to, or at, the seam. If your BC is quite old and appears to have a few pin-holes, the material is probably porous, and it’s time to consider a new one.
Checking for leaks with soapy water
4. Check the BC straps. This applies to both the stitching at the anchor-points as well as the webbing where it is pulled through buckles. This is particularly important on BCs that spend a lot of their life in swimming pools, because pool chemicals have a very detrimental long-term effect on BC fabrics.
5. Check the condition of the cylinder cam buckle. These can get damaged along with the scuba tank but remain undetected if you don’t unthread the webbing.
6. If your BC has an emergency inflation cylinder fitted, this must be tested on the same basis as your main diving cylinder: every 2.5 years. The trouble is that because it’s only you that has to fill it and not a compressor operator, you might not have noticed that it has become out of date. This is a pity and potentially very hazardous because these cylinders don’t have an easy life. They tend to get filled and emptied rapidly, and might also be flooded with seawater from the BC. The reliability of direct-feed units is so good these days that in my opinion it’s difficult to make a case for even having an emergency cylinder. Most manufacturers no longer fit them to BCs.
Perished corrugated hose crop
7. Every few dives, make up a weak sterilising solution (with the same stuff used to clean babies’ feeding bottles) and wash the inside of the BC. Thankfully, breathing the air out of a BC has not been a required skill for years, but there have been cases in the past of divers contracting unpleasant diseases such as aspergillosis or Legionnaires from BCs. Oral inflation of BCs is a required skill, so it still makes sense to ensure that your gear is hygienic.
Periodically disinfect mouthpiece and BC
8. Check the condition of both the corrugated hose and direct-feed hose. In particular look out for cracks caused by perishing and stress. Submerge the direct-feed unit with it connected to an air supply and check for leaks. If you find a trail of bubbles coming from the end of the hose, the hose-end O-ring will need changing.
9. Book your BC in for an annual service to get the inflator and dump-valves serviced.
Also on Divernet: Acquiring Perfect Buoyancy, The Elephant In The Pool