The hose in the pic used to be the short hose on my single tank rig. It burst just as I was getting ready for a dive, tank already on my back. My cylinder lost about 30 bar during the 10-15 seconds it took to shut it down. The hose was maybe half a year old and showed no outward signs of wear. There was no leakage before this failure; the leak occurred from one moment to the next without warning.

A closer look at the failed hose, now conveniently laid open, revealed that the material is unusually thin. I remember noticing before that this hose was more flexible than the others, but I didn't make the mental connection… well. Anyway, this increased flexibility probably allowed the hose to kink near the 1st stage fitting, gradually weakening the already thin material on the inside without making it look suspicious on the outside, until, one day, ka-PFFFF…

So this hose turned out to have been a piece of garbage, and that's why it failed. However, we know that failures happen even with well-kept quality gear. They certainly did happen to me. The question is, would a similar failure be a problem during a dive? And the answer is no, but you have to stick to procedures.

(Mmmmh, procedures…)

On a single cylinder, being able to end a dive without undue risk (like a rapid ascent from 30 meters) absolutely requires that you stay close to your teammates and remain aware of their location so you can reach them in time. Remember, 30-ish seconds? Secondly, all team members must keep sufficient gas reserves. How much is sufficient? Here's how much: Every diver must be able to complete an ascent at the planned speed, without omitting any stops, while sharing gas with another diver, and with both divers breathing heavier than usual due to all the excitement going on. This amount of gas is called rock bottom or minimum gas, depending on who you listen to. Depending on your depth, this amount can be rather large.*

Surprisingly, major gas leaks become a much less hairy issue on more complex dives where people use multiple tanks for redundancy: You shut down the failed cylinder, switch to your backup, and abort the dive as a team, breathing your own gas. Sharing is still an option, with reserve calculations based on the principles outlined above, but it's not your first, last, and only recourse. Isn't that great?

Training and practice – responding to gas leaks and other contingencies correctly and reliably, with minimal effort and no additional complications (hesitation, trapped or tangled hoses, loss of buoyancy, wrong regulator…) takes more than just strapping on an extra tank or two. If you're interested in learning more, ask me about sidemount and technical diving courses. The skills you pick up in these courses, and the underlying mindset, will make you an even safer diver than you already are – even when you go back to ostensibly easy dives on a single tank.

Oh, and don't buy crappy hoses like I did. There, I warned you.

Safe diving, Tim

* To give you an idea: Based on an AL80/11 liter tank, an average diver uses about 1.5 bar per minute on the surface. (Some more, some less, so don't assume this applies to you!) 1.5 bar/min on the surface translates to 6 bar/min at 30 meters. Multiply that by two (two divers sharing) and then again by two (stress), and you're easily at over 20 bar per minute. You need maybe one minute at bottom depth to get sorted, and then you need to do an ascent with all required stops, ideally without running out of gas… If you want to learn more about this, feel free to ask.

Divers typically start thinking about buying their own gear around the time of their Advanced Open Water course.  That's reasonable – by that time you know that you like diving, and chances are you've learned the hard way that rental gear comes in varying grades of quality, suitability, and fit.

Typical concerns of first-time buyers include cost (a complete set of gear is upwards of USD 1000), bulk/weight (you probably want to take it traveling), and lack of knowledge what to buy: There is so much equipment out there and so many people who sell it, it's easy to get confused and give up, or to end up being sold things you don't need.

In my first blog post on this site, I would like to give some suggestions to address these concerns – cost and weight/bulk by limiting your initial purchase to three small pieces of essential gear, and lack of knowledge with advice on what to look for when buying.

[Disclaimer: At the time of this writing, I am not involved in the sale of any of the equipment mentioned below and have no financial interest in the choices that you make. While I do sell regulators, I wouldn't recommend a getting a regulator as one of your first pieces of kit (even though they're awesome and very reasonably priced!)… anyway, here we go…]

Mask – Aside from looking cool, the main feature of a suitable mask is that it makes a good seal. You can test this by trying to make it stick to your face without using the strap. You should also be able to pinch your nose through the nose pocket and equalize your ears. Any mask that meets these criteria is a candidate, regardless of brand and price. Take your time to shop around if necessary, and don't settle for something that's only almost a good fit.

Secondary features that I like in a mask – but not everybody agrees, and I concede that a lot comes down to taste here – are that it is low volume (easy to equalize, fits in a pocket), has a black skirt to minimize stray light coming in from the sides (may seem darker in the shop, but lets you see better when actually diving), and that it is constructed as simply as possible: One or two panes of tempered glass, a rubber or silicon skirt with nose pocket, a solidly attached strap. No fancy clutter like angled lenses or drain valves. A good quality mask can be relatively inexpensive. Don't go for the bottom shelf, but if you want spend more than eighty dollars (US) then you better have a good reason.

Surface marker buoy - SMB, inflatable signal tube, safety sausage: Call it what you will, this very affordable piece of equipment vastly improves your safety. Deploy it from underwater to mark your location before ascending so you won't get run over by a boat. After surfacing, an SMB helps to get the attention of your boat to pick you up. In an emergency (you're adrift at sea; may it never happen), it very much improves your chances of getting spotted by rescuers.

SMBs come in a range of shapes and sizes. A length of about a meter or 1.20 m should be plenty in most cases. Make sure it has a one-way (duckbill) valve at one end, as well as a pressure relief/dump valve with a small cord. Some SMBs come with an oral inflation valve. Color should be bright (usually orange, but there may be local rules on the significance of different color SMBs). Brand doesn't matter; however, the better ones have stitched (as opposed to glued) seams. To deploy your SMB from underwater, you will also need a spool and a double-ended carabiner.

Dive computer – I have much stronger opinions about the makes and models of dive computers than I have about those of masks and SMBs. I've tried quite a few, seen many more, and spent way too much on stuff I don't need. So without further ado, and before you run off and burn the family fortune on an overpriced piece of feature-rich, impractical junk like a Suunto D6i (upwards of USD 700), consider if a Mares Puck Pro (under USD 200) might suit your needs.

The Mares Puck Pro is a minimalistic computer that gives you all the features you're likely to ever need this side of technical dives with three or more gases – and nothing else. It indicates depth and bottom time on a large, easy to read display. It calculates sensible amounts of NDL and deco time with three different conservatism settings. It monitors your ascent rate and Nitrox MOD. It has a logbook and a dive planning mode. It has a USB interface to connect to your PC, and it uses a commonly available battery that you can change at home. Unlike other units in its price range that I could name, the Puck is also very solidly built and durable.

There is more: If you ever want to get into technical diving, the Puck Pro lets you do accelerated decompression with one gas switch. If you want to get even more technical, you can set it to gauge mode, turning it into a perfectly fine bottom timer for trimix dives with a maximum depth rating of 150 meters. Only downside: As the name suggests, it's not watch-sized. Then again, it's not as big as the name suggests.

There are three reasons why you might not want a Mares Puck Pro: 1) You are very certain that you need something watch-sized to wear at the dinner table, in which case I can only shrug my shoulders and suggest you get an Oceanic Geo, by all accounts a decent choice; 2) You've let somebody convince you that you need a computer that doubles as a compass, shows you how much gas you have in your cylinder, and drives everybody nuts by beeping and flashing with seven different kinds of alarms –– extra annoying if several divers in a group have a computer like that; it makes your safety stops sound like an arcade game parlor, and remember how hard it is to pinpoint the origin of sound underwater? beep! was that me or you? beep! beep! or him? beep! agnnn… –– in which case I am overwhelmed with sadness at this tragic waste of at least half a thousand dollars that would be much better spent on training with a quality instructor, or travel, or hard liquor; 3) You actually do need a top-of-the line computer with fully configurable decompression algorithms that does trimix and multiple gas switches and can be used with a rebreather, in which case I'm going to recommend you a Shearwater Perdix or Shearwater Petrel. These are among the best dive computers on the market today, and at around USD 850, they're still a far cry from the top end of the price range. (And incidentally, the kind of dive that you want this kind of computer for is also the kind of dive where your trusty old Puck Pro comes in handy as a back-up bottom timer. So there you go. Mask, SMB, Puck. All you need for now. Figure out the rest later.)

Whoa, so this post has become rather long, and there are no pictures.

Hope you enjoyed reading it anyway,
stay safe and happy diving,

Tim

0 Comments