piston vs. diaphragm for backgas in puget sound

[Paulicarp]

Hog now has their new balanced piston 1st stage on the market, and it raises a new question for me that I have a feeling many of you have hashed over before in the old debates between ScubaPro/Atomic/Apeks etc. But rather than debating brand vs. brand, I'm trying to decide between using the HOG balanced, sealed diaphragm vs. the new HOG balanced piston non-sealed first stages for backgas. (understanding there may be different issues at play with deco/stage applications)

From what I think I have learned so far:

1) flow rate is a non issue, as both flow more than enough gas.

2) the primary advantage of the piston design over diaphragm design is simplicity.

3) the primary drawback of the piston reg is that it is not sealed. (I'm not sure if it can aftermarket sealed or not)


So...for backgas regs in cold salt water, which would you choose and why?

[trevorrowe]

So...for backgas regs in cold salt water, which would you choose and why?

Man, I had the exact same question this morning, and inquiring minds want to know!

[Nwbrewer]

Hog now has their new balanced piston 1st stage on the market, and it raises a new question for me that I have a feeling many of you have hashed over before in the old debates between ScubaPro/Atomic/Apeks etc. But rather than debating brand vs. brand, I'm trying to decide between using the HOG balanced, sealed diaphragm vs. the new HOG balanced piston non-sealed first stages for backgas. (understanding there may be different issues at play with deco/stage applications)

From what I think I have learned so far:

1) flow rate is a non issue, as both flow more than enough gas.

2) the primary advantage of the piston design over diaphragm design is simplicity.

3) the primary drawback of the piston reg is that it is not sealed. (I'm not sure if it can aftermarket sealed or not)


So...for backgas regs in cold salt water, which would you choose and why?

I'm probably talking out of my ass, but I was under the impression that piston regs (unsealed) were more likely to freeze up in the cold, and required more attention to the maintenance in salt water.

[ljjames]

i've been diving piston (Scubapro) almost exclusively since 1993-ish. I have taken them deep, shallow, in high current, under waterfalls, diving in freezing weather, and diving on the east side of the mountains under ice. I have not had any issues with freezing up. I have also not had any that had to be removed from service due to corrosion.

some of them have quite literally been in use since the early 90's with thousand or so dives as primary before being relegated to stage bottles for their next thousand.

i have one diaphragm, on my argon bottle. it seems just fine too

oh wait... i have a couple diaphragm apeks regs on the meg... i have not seen any freezing issue with them either (though not a fair contest as application is a bit different)

these days i'm not terribly picky, except for the "same breed in the stable" thing, if only for some interchangeability with regards to regulator guts

[Grateful Diver]

Depends on what you mean by cold.

Puget Sound rarely gets below mid-40's. At that temp, piston regs are unlikely to freeze. I've been using MK-25's for my backgas regs (both singles and doubles) for about three years now without a single freeflow ... that's about 700+ Puget Sound dives without a problem.

I see a lot of both pistons and diaphragms in common useage among tech divers here. So I don't really think our local conditions are cold enough for it to be a concern.

Now ... if you're planning to take up ice diving, perhaps a diaphragm reg might be a good idea ...

... Bob (Grateful DIver)

[Sockmonkey]

Airspeed press' regulator book makes a funny mention about diaphragm 1st stages being better for folks who don't take care of their gear. When I read it I thought... oh no... I didn't rinse my mk25's the last time I dove! Ack corrosion!

Having never serviced a piston 1st stage I can't say how true that is... but either way it was a delightfully honest bonus feature of a sealed reg. It makes for good marketing too "Are you a lazy diver? Buy a sealed diagraghm 1st stage!"

I'd vote for the HOG regs just because of the price and the rebuild kits are available for you to service it yourself. I wish scubapro did the same.... stupid scubapro.

-Eric

[CaptnJack]

Focus on the hose routing, and servicability - not sealed diaphram vs unsealed etc.

You aren't going to freeze up a reg in Puget Sound (or Lake WA for that matter), "cold" as far as icing goes starts at about 39F for freshwater and 36F for salt. Getting a dry fill is actually more important.

[ArcticDiver]

For what it is worth I've used diaphram regs down to +30 and piston to +45 or so in sea water. No problems with either. But, just based on design and superstion I only have diaphram regs now. But, compared to you folks who practicaly live in the ocean I'm a rank desert rat.

[kagey747]

I dive scubapro MK 17's (sealed) on my doubles rigs because I like the routing. All my stages/backups are diaphram too, because I like the simplicity. My single rig is a piston (MK 25). I have seen no difference between them as far as performance during actual dives- I cannot overbreath any of them, and I'm an air-hog. Go with the one that "fits" best with your configuration (and pocket).

[Paulicarp]

Is it generally true that when a piston reg floods it does not stop delivering gas, but a diaphragm reg might?

It seems to me that this would be a compelling reason to choose piston. Swapping regs underwater isn't something I plan to do, but doesn't it make sense to have the greatest likelihood of being able to do so successfully if the need arises?

[CaptnJack]

Is it generally true that when a piston reg floods it does not stop delivering gas, but a diaphragm reg might?

It seems to me that this would be a compelling reason to choose piston. Swapping regs underwater isn't something I plan to do, but doesn't it make sense to have the greatest likelihood of being able to do so successfully if the need arises?

Its really not an issue. Focus on the important things like service, servicing, O2 cleaning, parts, hose routing, ports, etc.

[Paulicarp]

Its really not an issue. Focus on the important things like service, servicing, O2 cleaning, parts, hose routing, ports, etc.

I'd vote for the HOG regs just because of the price and the rebuild kits are available for you to service it yourself. I wish scubapro did the same.... stupid scubapro.

-Eric

Remember, this question is between two HOG regs with identical hose routing, port count, availability of rebuild kits, etc. The difference is that one is unsealed piston for a few bucks more, the other is sealed diaphragm for a few bucks less. That said, I guess I'm running out of reasons to pay the extra few bucks for the piston version.

...but it does look cool...

[Nwbrewer]

Its really not an issue. Focus on the important things like service, servicing, O2 cleaning, parts, hose routing, ports, etc.

I'd vote for the HOG regs just because of the price and the rebuild kits are available for you to service it yourself. I wish scubapro did the same.... stupid scubapro.

-Eric

Remember, this question is between two HOG regs with identical hose routing, port count, availability of rebuild kits, etc. The difference is that one is unsealed piston for a few bucks more, the other is sealed diaphragm for a few bucks less. That said, I guess I'm running out of reasons to pay the extra few bucks for the piston version.

...but it does look cool...

Add the few $$ to your scooter fund.