Sealed VS piston regulators.

I currently have an older Zeagle branded Apeks built sealed 1st stage, 50-d comes to mind. Anyways its a nice sealed regulator and I like the way it breathes. Not that I have owned a bunch.. "only one" but I have used a few rental gear and didn't enjoy them as much. For all I know I have a basic reg or I have a really nice one not sure yet still learning about the hardware.

Anyways to my question, sealed VS piston does it really matter? I know they say sealed for colder diving but how cold would you consider cold before you look for a sealed unit? I live in Seattle and dive year round, its not freezing but 45 degree is colder then Florida. I know lots of people dive with piston around here but is there a reason to avoid the sealed unit?

My goal is to buy gear once and not over and over again, my LDS used to push Atomic M1 I believe but over the past year or so have moved to Halcyon piston style of regs. In the end I can buy what ever I want and like but should I be concerned about the style sealed VS piston?
This shop also isn't a fan of Apeks, they supposedly used to sell them but had issues with the HP seat as I understand it but again I believe this was years ago.
In the end does it really matter the brand as long as it is a decent brand?

Goals in the next year are, doubles, deeper diving, deco ETC.
So I am looking for 2 regs for the doubles and maybe for the deco bottle, not sure I want a dedicated deco reg but I guess that leads to the next Q.

Deco regulator? do I need a dedicated smaller reg or will a full size work as well?

so. long can of worms and search function is your friend.
You can technically seal piston regs, you pack the piston housing with grease, it's a pain in the ass and messy. Sherwood pistons with the bleed valve are environmentally sealed because they have a controlled leak essentially.
The regs you rented were not as nice because the second stages are usually detuned to prevent freeflow and has little to do with the first stage. All of the current balanced *this is key* first stages can only be discerned in breathability by a computer, no human can tell the difference, all of that is in the second stage. With a first stage you set the IP to somewhere around 125PsIi and that's about it.

Now, Halcyon pistons are made in Taiwan and are very simple regs, but very expensive because you are paying the blue H tax. Apeks are the preferred brand in England, shock of all shocks, and it is true that they did have a bad batch of HP seats a few years ago. Most of the modern regulators are copies of the Apeks ATX design, this is true of HOG, DiveRite, Hollis, etc. There is a very active DIR community in Seattle, with quite a few of them being very active on this board, so my suggestion is to dive with them and avoid LDS's like the plague because you'll save so much money avoiding them for anything other than fills.

As far as cold is concerned. The concern with cold has almost nothing to do with the water temperature but everything to do with the air temperature. First stages can freeze very easily when the water temp is cold and the air temp is below freezing because of the depressurization in the first stage. This is why if you open a tank valve and let it bleed off the tank valve will usually have frost on it and the tank is very cold, PV=nRT. So, if you don't use the first stage above water after it gets wet, it'll be fine if it is unsealed, but it is still preferred to have sealed diaphragm regulators for ice diving and what not. Diaphragm regs are much easier to tune after rebuild despite a slightly more complex inner workings. You can adjust the IP with an allen key instead of having to shim the piston.

Recommendations: Buy a Hog doubles set in either D3 Zeniths, or the D1 classics, your call, they're basically the same, the zeniths just look sexier. If you don't want to use the second first stage, just save it for when you need it. You can learn to service these yourself and you need to if you are planning on technical diving
You need a dedicated deco regulator, the regulator configuration is very different than that for back gas. Your current zeagle is perfectly fine for a deco reg or if you get a dedicated doubles reg set you can swap it between deco and recreational singles.
Don't pay the Blue H tax, it's not worth it. Probably close to $900 for a singles set, Atomic is probably worse.
Hog D3 Doubles Package - Dive Right in Scuba
$800 for a doubles set, with SPG, braided hoses all around, and really sexy looking to boot. Combine that with the amount of money you can save in doing service yourself and it's a no brainer which is why so many of us are proponents of these regulators. Wait until Black Friday if you can, HOG is notorious for putting out stupid sale prices on their products for the BF sales

For all intents and purposes, Scubapro and Halcyon regs are the exact same minus the Blue H Cap.
Mk 25 for Halcyon Piston, Mk 17 for Diaphragm.

tbone1004 hit the head on environmentally sealed regs and when you would need them.
If you're looking at diving in muck, silt, and generally lots of precipitate in the water, then Diaphragm (talking non-environmentally sealed) regs will win out as lower rinse maintenance. Piston regs will collect all that silt in the first stage if you just dunk rinse it rather than soak and slosh. Diaphragm, not so much because they have a much smaller portion exposed.

All the high end regs with each manufacture will breath the same, as far as human perception goes.

Difference between Diapraghm and Piston comes down to maintenance. Balanced Pistons are comparable to Diaphragms now days in terms of air flow.
Deco bottles, you may want to go with a low end unbalanced piston reg since you'll be utilizing them shallow and if need be you can flood and swap regs without too much of a headache in maintenance afterwards. There are preferences that say otherwise though. It will come down to your preference after you get the training.

And also if you're going tech, get 300bar DIN regs or regs that can later be converted to DIN.
300bar DIN regs can be used in all types of tanks valves.
You'll be using DIN exclusively in the tech world. And if you go on a dive trip, you can plug in a yoke converter to your reg to use Yoke Tanks.

keep your reg if you like at and service for it is available.
the science has not changed and neither has the internal design, so no need to replace a working piece of equipment.
piston regs can deliver more air per design than diaphragm regs can but both designs will provide you with more air than you can breathe.

tbone1004:

Diaphragm regs are much easier to tune after rebuild despite a slightly more complex inner workings. You can adjust the IP with an allen key instead of having to shim the piston.

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I just serviced my Cressi AC2. Tuning the IP is as simple as turning an adjustment ring (and can be done without the spanner referenced in the service manual). The internal is simple and the service manual is online. I can break it down, clean it, reassemble and set the IP in less than a half hour. Doesn't get much easier than that.

As far as an unbalanced piston accumulating silt etc. - I call bushwah. I volunteer dive many times a year removing mats for milfoil remediation. It doesn't get any muckier/siltier than that. Touch the mat and vis is zero and stays that way. I rinse my regs well when I get home and have never had accumulation of silt or muck. I service my own regs so I know what they look like inside.

All the Atomic line except maybe the Z series is available sealed for $40 more.

Some of the pistons now are done with adjustment rings, you are correct, but not all.

Re. silt, they aren't as likely if the water is silty, it's more dragging them through silt or if they are resting in silt like a lot of stages and deco bottles do or in river diving. I think the AC2 is quite different than many of the other piston regs out there that get the rap of holding silt. There have been many modern advances since the old sherwood designs.

tbone1004:

Some of the pistons now are done with adjustment rings, you are correct, but not all.

Re. silt, they aren't as likely if the water is silty, it's more dragging them through silt or if they are resting in silt like a lot of stages and deco bottles do or in river diving. I think the AC2 is quite different than many of the other piston regs out there that get the rap of holding silt. There have been many modern advances since the old sherwood designs.

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I don't know - My AC2 is at least 4-5 years old so I'm not sure what you mean by "now" and "modern advances". Also, the AC2 is probably the least expensive reg set you can buy. Wouldn't expect it to have the most advanced features. Could be wrong though - I often am.

Never though of dragging through or laying my 1st stage into the muck. Sounds odd. Also, are you doing deco dives in rivers. Didn't know there were any that deep.

pony bottle in rivers can get quite a bit of muck in there when you are digging up the muck and the river is flowing that right into the first stage. I.e. fossil diving. Other common one is laying a tank down in a cave and while you try to keep them out of the muck when possible, sometimes it is unavoidable.

re. ac2, I think it's just the size of the holds for the balance chamber in the AC2, at least by the pictures make them look a lot smaller than the relatively large ones. Having the adjustment ring is a huge advancement over the old designs though that had to be shimmed to change the IP, a few o the SP pistons are like that as well.

tbone1004:

pony bottle in rivers can get quite a bit of muck in there when you are digging up the muck and the river is flowing that right into the first stage. I.e. fossil diving. Other common one is laying a tank down in a cave and while you try to keep them out of the muck when possible, sometimes it is unavoidable.

re. ac2, I think it's just the size of the holds for the balance chamber in the AC2, at least by the pictures make them look a lot smaller than the relatively large ones. Having the adjustment ring is a huge advancement over the old designs though that had to be shimmed to change the IP, a few o the SP pistons are like that as well.

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Oh, fossil diving. Probably the same for treasure (metal detector) hunters.

If I had to use shims to adjust I'd scream. I've done that on bearings in a Troy Built rototiller rebuild. What a PITA. Doing it once a year or more would be way too much. Thank goodness I got lucky in my choice of reg.