One BCD gear setup is NOT universal (opinion only)

[DogDiver]

If that tank's main valve O-ring ever blows out, you may change your beliefs regarding pony bottles. Ditto if it ever somehow gets trash in it that blocks the dip tube.

Personally, there is no shallow reef dive that I would ever do where I would prefer something other than the same rig I would use for the most advanced single tank diving that I would do.

My only reason for wanting to have 2 single tank rigs is to have one with more lift, for diving dry in cold water, and one that is more streamlined, for warm water. And that is just the BCD. I'll use the same reg set and just put on or remove the dry suit inflator hose as needed.

I realize that you are a lot more experienced than I am, so maybe my concerns about a single tank with an H or Y valve seem like nervous newbie nattering. Maybe I'm paranoid because of lack of experience to give me more confidence. But, if I am ever diving where I feel a need for the redundancy of an H valve, I will just use actual doubles. Side mount or back mount, depending on specifics. I dive back mount doubles most of the time, anyway, even for shallow reef dives.

I’ve seen my fair share of blowen neck O rings where the valve was only tightened hand tight per manufacturer instructions. That’s why in cave country where overpressuring to 3800+ psi is the norm. We tighten the valves after annual service with a 20 inch wrench. No blowen O rings that way.

 

[PfcAJ]

As your aware sea water is heavier than fresh water, so your exiting in fresh water.

But it touched it! It’s ruined and apt to fail at any second!!!

 

[MaxBottomtime]

Personally, there is no shallow reef dive that I would ever do where I would prefer something other than the same rig I would use for the most advanced single tank diving that I would do.

My only reason for wanting to have 2 single tank rigs is to have one with more lift, for diving dry in cold water, and one that is more streamlined, for warm water. And that is just the BCD. I'll use the same reg set and just put on or remove the dry suit inflator hose as needed.

This, except that I use the same Freedom plate and wing for diving a reef in the Philippines wearing a dive skin as well as diving a drysuit in Canada. I used the same backplate and wing for two decades of diving deep with doubles and deco bottles. The single tank rig is the same one I've used for ten years. It works everywhere.

 

[jlcnuke]

I’ve seen my fair share of blowen neck O rings where the valve was only tightened hand tight per manufacturer instructions. That’s why in cave country where overpressuring to 3800+ psi is the norm. We tighten the valves after annual service with a 20 inch wrench. No blowen O rings that way.

Ouch... overtightening an o-ring is actually a good way to ruin the seal it's supposed to make, not make it better. That's simply how they work. Glad it hasn't screwed you over yet though.