So let me set the scene for you:
You're on a liveaboard getting ready for a dive. You hook up your first stage to your tank, tighten down the yoke, slowly turn on the air. All of a sudden, you hear a pop and a slight hissing. Uh-oh! You turn the air off, slowly purge the system, loosen the yoke and take the apparatus off. You are shocked to discover your o-ring broke and now you need a new one. Luckily, you had an extra o-ring in your save-a-dive kit. You replace your o-ring, retry setting everything back up. It works, and now you go off happily diving.
So this leads to my question. While I have not had to do any repairs on my own equipment since I'm still relatively new to diving, I was wondering how much of my equipment I should learn. I want to go on a liveaboard, but I'm not ready to book one until I know my equipment to the point where I can fix something myself should an issue arise. This being said, how far along my gear should I learn? Has anybody every had to take a regulator completely apart and replace internal components? Ever had to patch a dry suit? Stitch up a BCD? etc. etc.
In short, I want to know how in depth I should understand my own equipment in the one in a million chance I get stranded on a deserted island with nothing but my own gear/tools and the only way for me to survive is to fix a sabotaged piece of equipment and dive underwater to avoid being shot by pirates patrolling the island above water
lol . . . but no, just want to know how much I should learn for real-life fix scenarios
First you have to decide how much time and effort you want to spend learning how to repair stuff. Then you have to decide how much time you want to spend repairing stuff on vacation.
One thing that has not been mentioned yet:
Number 1 rule of scuba repair is DON'T FIX ANYBODY ELSES STUFF, unless you have been trained by the manufacturer to fix it and are getting paid to do it.
If you ignore rule 1, and anything bad happens to the person you made the repair for (doesn't have to be related to the repair), everyone else on the boat will be looking at you wondering what you did that almost killed someone. Then things will start going downhill for you.
Next is my level of difficulty rating scale for scuba stuff repairs.
Level 1 -You can change o rings on a tank valve, replace mask straps and fin straps, and can use Aquaseal to patch holes and unraveling seams (but you still get Aquaseal all over everything else in addition to the repair)
Level 2 -You can take hoses off, replace o rings on them and put the hoses back on with everthing hanging off the regulator in the correct direction. You still get Aquaseal all over everything every time you open the tube.
Level 3 -You can replace a mouthpiece. You can replace a BCD valve (just replace the whole thing with a spare, not take it apart). You can take your second stage valve cover off and clean out the sand, dry salt, seaweed and jellyfish tentacles. You can replace the valve cover without damaging it. You can take BCD exhaust valves apart, clean out debris and replace the valve. You can patch a hole in a dry suit. You might be able to thread straps through a back plate and get all the hardware in place facing the correct directions on the first try. Aqualseal is still a challenge.
Level 4 -This level is currently not assigned and is reserved for future use
Level 5 -You have bought books, specialized tools and have educated yourself in repairing regulators. You may have taken a course specific for 1 type of regulator repair. You are comfortable disassembling, cleaning and reassembling a regulator and are confident diving it. You know what types of o rings and lube to use for nitrox. You can take apart a BCD valve and repair it. You might be able to take apart a tank valve, or you might not care to learn tank valves. You swear you will never open another tube of Aquaseal and just buy new stuff instead.
Level 6 -You discovered you can get cheap, old regulators on EBay. You really enjoy taking things apart and putting them back together. You now have more than a dozen regulators you have rebuilt. You will never dive all of them. And you still can't stop checking to see what's currently for sale on EBay. You still don't care to learn about tank valves. You still have dried remnants of Aquaseal all over your work bench.
Level 7-9 -Reserved for future use. I just haven't decided where the following belongs in these groups:
replace dry suit wrist and neck seals, sew you old falling apart BCD back together again
Level 10 -You know how to repair any regulator ever manufactured. You currently own a Mark V diving hat and full dress that you restored and it is ready to dive.
Level 11 -You can make a tank out of a block of aluminum. You can make your own regulators out of plastic or brass.
Open water students should be at Level 1 before they get their certs. A lot of people are happy at that level and never progress any further. They just want to dive and not have to mess with their stuff much.
I think after 1 year, that most divers that dive more than once a year on a tropical vacation, should learn enough to be at Level 3. But if they don't want to do that, that's OK too as long as they get their gear regularly serviced at a good LDS.
I think I am currently somewhere just below Level 10. (except for threading the back plate thing, I still never get it right on the first try)
