Gauges-Why Bother?

[ba_hiker]

I did three dives this summer in a lake where the bottom is mostly about 30 ft. To get to 40 ft, in the deepest part of the lake would take a shovel. Nobody was wearing depth gauges. Only a few used SPGs. No one did safety stops either.

Of course at 30 ft the NDL is something like 150 minutes, and I can't reach that in two dives with 80s.

 

[Puffer Fish]

This is not a troll, but I am playing the Devil's Advocate.

I have a decent, not exceptional SCR of 15 LPM or .5 CFM. With a standard 80 cf tank air is always the limiting factor when diving depths of less than 70 feet.

In my area dive shops commonly offer DM lead double shore dives. All divers wear computers but the DM's NEVER look at them or ask people for their individual deco load. Surface intervals are always one hour. Most dives are 18m (60ft) or less.

I have completed dives to 150ft and often use nitrox on dives between 25 and 35 meters so I am certainly not saying that gauges have no place. My question is for shallow dives (<70 ft) that are all many divers do, why bother with anything but an SPG?

You raise a couple of points, but the primary one is: Why carry gauges when they are not needed.

1. First is the issue of learning to use them, and be comfortable with them. That means you use them, even when they are not needed. I would assume that the "lead" dives are mostly with new divers, and it is new divers that need the practice the most.

2. Your comment "Most dives are 18m (60ft) or less" implies that there are deeper dives possible. And it is possible to get a deco obligation at 70 ft (just had this happen two weeks ago, on the first dive).

3. How did anyone know what the depth was, without a gauge?

4. Sometimes, things don't go as planned. Just had a dive on wreck that was sitting at 65 ft, so why worry about gauges? Well the front of the ship had been changed by a storm, and now the bottom, in that area was 85 ft. Dive planning and the experience of others was wrong.

As far as the bottom of a 30 ft deep lake goes...obviously not needed, but I wear a kit of gear for every dive and that includes gauges (I would not spend a lot of time looking at them, but I would have them)

Oh, and when running a shop in the 70's, we would not fill a tank with the J valve put on backwards for safety reasons. People died doing that.

 

[jpcpat]

True, you don't really need a computer or depth guage for shallow reef diving while following a DM. If you lose track of the DM, things change, so I prefer to have it . I also think it's just a bad habit to get reliant an someone else for my safety.

As for diving without anyone having a depth guage/comp. I think it's better to have them on every dive and be used to checking them...often

 

[Charlie99]

I have a decent, not exceptional SCR of 15 LPM or .5 CFM. With a standard 80 cf tank air is always the limiting factor when diving depths of less than 70 feet.

My question is for shallow dives (<70 ft) that are all many divers do, why bother with anything but an SPG?

I agree with your basic concept, but there are a couple glitches. First of all, you need to know the divesite well enough that you really are sure that you are going to be at the depths you assume.

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The second point is for a square profile (flat bottomed divesite) 70' is plenty deep enough that you have to pay attention to time. At the just over 3ata of 70', you will exceed 40 minutes and still have >500psi left. Obviously, if you were really mellow and calm some day and SAC was lower than 0.5, then dive time can be even longer. So you should really have a timer even for a single dive to 70' flat bottoom.

Then you need to take into account your repetitive dive. At 0.5cfm, using the first 2500psi of a AL80 of air tank, and a 1 hour SI, and a tank ofyou are still beyond NDL on the second dive on two 60' dives.

Two 50' square bottom dives on air with an hour SI between them will be just a bit inside NDL for 0.5CFM NDL, and outside NDL for 2 dives at 0.4cfm.

Only for a square profile dive to 40' (AL80, 0.5CFM) can you be reasonable certain that ignoring time is OK for two dives with 1 hour SI.

Charlie Allen

 

[FishDiver]

Thanks for the replies so far. I am not actually recommending that people dive without timers, depth gauges or computers. I posed the question to learn more about their actual utility. What is actually useful, and what is more related to marketing or litigation.

I notice in my diving that I rarely use my computer to plan my dives. I monitor my depth and dive time frequently during dives, but mostly out of curiosity rather than any real need to know. Depth is useful for navigation and for monitoring ascent rates.

I own a computer because I bought new regs last year and needed new gauges. The computer cost little more than buying a separate timer and depth gauge.

Businesses make money convincing people that the gear they currently own is obsolete, and the safety mavens insist that last year's cutting-edge safety options are now mandatory.

 

[jeffrey-c]

When I started diving, we had no .......

Why, when I started driving, we tied boards to our feet since fins weren't invented yet. And we didn't have regulators or tanks, so we took empty bleach jugs and tied weights onto them so they'd sink, and we'd suck some air out of one every once in awhile just before passing out under water. And wetsuits hadn't been invented, so we'd slather lard all over our bodies for some insulation. And we didn't have any ..............

 

[TSandM]

I apologize -- a, for posting as my husband (thought I'd put a disclaimer on the original post when I recognized that, but I guess I didn't) and b) for misquoting him. It was PRESSURE GAUGES they didn't have, not depth gauges.