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Just wanted to point out that Dive Paradise is out of Hotel Cozumel and they have big slow boats for their trips. We watched lots of very big unhealthy people getting in and out. Most boats had at least 12 to 14 in them. If it's you and your buddies and you all want to dive together I can understand why that would be fun but as a practice I must say that diving is risky and that's probably not the best way to maintain equipment when you have so many people packing into a boat.

Look, I know this is probably going to rub people the wrong way but the health of many American divers is really really poor these days. If you are in your forties and older and you are morbidly obese and the majority of Americans are such... and many are extremely morbidly obese... so much so that I watched a woman, who obviously loves to dive, is holding about a 100 pounds of extra weight on her frame and as such needed several people to get her and her husband in-and-out of the boat every day with this operation. Many of you are beautiful souls and I want to see you make more and more dives and bring that wonderful energy back to the reefs over and over. I want to dive with you folks in the future and all I could think of while people were boarding was "what do they do in an emergency at depth with that many people?". This isn't a lecture, just a suggestion with the CV pandemic, you are at grave risk with this weight and your age.

The OP has a great point about staying close to your buddy. I tell everyone on the boat I have a bright neon yellow/green octo with your name on it. I check it everytime I descend and I remember vividly at around dive 20...10 years ago when I was around 80' with a dive op in Roatan and struggled to pull air through their rental reg. I said, no more because when we got back to shore it was removed and a couple of days later was back in the mix with no change out of the apparatus (I marked the reg strategically once we got back to see if a joint was opened up to service it). It had not been done. I said never again and bought a reg as soon as I got home. I realize large ops are factory diver machines and it's about bodies, time, cash and boats. It's a biz, I know. I dove with a long time DM at DP who was now with another op. He said he had concerns about such a large outfit and their ability to take care of everyone underwater.

DP is probably 95% a perfect outfit and that's why it's such an economical choice in COZ. Many of the guests there knew all the staff and had dove for decades with them and it was great to see the hugs and conversations. No wonder people keep coming back but as an outside viewer all I see is potential for more experiences like what the OP had.
 
Your own gear won't help if debris in the tank clogged the valve.
True, except they tried that reg on other tanks with same result, so not in this case. Regardless, traveling with as much of your own gear as you can eliminate more possibility of using poorly maintained rental crap (presuming you take care of your own crap and test it before the trip).
 
True, except they tried that reg on other tanks with same result, so not in this case. Regardless, traveling with as much of your own gear as you can eliminate more possibility of using poorly maintained rental crap (presuming you take care of your own crap and test it before the trip).
Oh, and carry a second 1st stage if you can in case the first one gets “clogged” beyond repair on a boat. I know, I know, now we’re hauling too much stuff, yadda, yadda.
 
HP seats are basically a tiny chunk of nylon glued into a little brass cup. If the glue comes undone they tend to stay put from pressure BUT... If they come loose they will smush into a downstream hole leading to the LP hose
Pressure on yours is holding them shut? Both air pressure and spring pressure are attempting to open mine. The only thing that closes it is IP air pressure. What brand do you have? My HP nylon that seals the seat isn't glued in at all and if it ever came out, which it can't I would get full tank pressure to the second stage.
 
Pressure on yours is holding them shut? Both air pressure and spring pressure are attempting to open mine. The only thing that closes it is IP air pressure. What brand do you have? My HP nylon that seals the seat isn't glued in at all and if it ever came out, which it can't I would get full tank pressure to the second stage.
Pressure holds the actual seat to the seat holder in most 1st stages. Sometimes they are a loose seat and sometimes they are attached to a metal holder
If the seat comes loose in the 1st stage like due to a spring failure, then the chunk of nylon will try to force its way into the second stage. It usually doesn't actually get into the hose - it wedges into the hole exiting the first stage. Depending on how its wedged it can completely cut off flow to the main 2nd stage and your backup/octo then free flows because there's full tank pressure on the LP side. Kinda rare but not impossible and certainly has happened.
 
Pressure holds the actual seat to the seat holder in most 1st stages. Sometimes they are a loose seat and sometimes they are attached to a metal holder
If the seat comes loose in the 1st stage like due to a spring failure, then the chunk of nylon will try to force its way into the second stage. It usually doesn't actually get into the hose - it wedges into the hole exiting the first stage. Depending on how its wedged it can completely cut off flow to the main 2nd stage and your backup/octo then free flows because there's full tank pressure on the LP side. Kinda rare but not impossible and certainly has happened.
In this case there was no air at the backup second stage either. I'm having a hard time believing that the nylon got cur in two and immediately clogged both LP lines so that 1000 psi wouldn't push air through. If the spring broke and collapsed the IP would go way low. There would still be air at the second stages until the IP was zero.
 
I don't want to name a brand, but it was one of the clones based on Apex. The owner was of course interested to find out how the reg had failed closed, and as a certified tech on that brand, his determination was that the soft part of the hp seat had indeed separated from the brass cup and lodged in an air passage, I don't remember exactly where. I have always used H valves and redundant regs for sports diving, religiously after this episode.
 
I also have seen a similar problem due to debris (mostly rust) clogging the metal filter of the reg (not the dip pipe). The interesting point is that when this happens, the SPG still indicates the true pressure in the tank, as the minimal air passage remained is enough for pressurizing the SPG. But when you inhale, then the indicated pressure drops, and then comes up again slowly...

We did see that very thing happen a number of times on other dives, both to us and to other divers, but it wasn’t happening during this dive.

—wife/buddy of deepfix
 
The seat on the first stage of a piston regulator won't come out unless for some reason it has broken into two or three pieces. Then these pieces can come loose. But this would allow full tank pressure into the low pressure area, and unless all three ports are blocked will free flow the regulators.

A diaphragm regulator has a pin which goes through the regulator from under the diaphragm, and pushes the high pressure holder from inside the low pressure area of the stage. If this pin breaks, the regulator has no way of opening the seat, and no air will flow.

So looking at these two scenarios, I think it was a diaphragm regulator which suffered a catestrophic pin break which caused this situation. If this was a knockoff cheap regulator mimicking the Apeks diaphragm regulator, the manufacturer may has used a cheaper, lighter weight than needed, or materials that were not stainless steel for this pin, and it broke.

The specifics on the regulator would be very helpful in this case.

SeaRat
 
https://www.shearwater.com/products/perdix-ai/

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