Piston vs. Diaphragm?

I did some searching and didn't really find much…

Which is a better regulator design, piston or diaphragm? From what I'm seeing, piston looks to be the choice of most of the more top rated brands of regulators. What's the pros and con of each design? Does one or the other have an advantage in certain types of diving (IE, cold, deep, etc). I never really found a definitve answer...

I've tried out many regulators and did research and finally bought an Atomic B2 which has a balanced piston design. Great reg and the easiest breather I've used.

It's only a matter of personal preference/bias.

Piston regulators (at least the high end ones) are supposed to have better flow rates/performance, but the diaphragm ones are now pretty much the same. Not that you can tell the difference anyway, as any mid ranged 1st stage can outperform the best performing 2nd stage you attach to it, so it's more about marketing then air delivery. The 2nd stage is the bottleneck, not the 1st stage, IMO.

The term bottleneck should also be taken with a grain of salt, as I have no problems with air delivery from my 2nd's.

If you want something that makes a difference, then look for simplicity in design, fewer moving parts, reliability and etc.

I agree with the above mentioned, except the verbage must include the word "balanced/ over balanced" diaphragm.

A true diaphragm has the least amount of parts and cannot be beat for reliability. A balanced / over balanced diaphragm increases pressure as you go deeper (same as a piston) a unbalanced diaphragm like the SP Mark 2 does not.

serrada:

A true diaphragm has the least amount of parts and cannot be beat for reliability. A balanced / over balanced diaphragm increases pressure as you go deeper (same as a piston) a unbalanced diaphragm like the SP Mark 2 does not.

Click to expand...

Unbalanced piston like SP MK2(+)....

serrada:

I agree with the above mentioned, except the verbage must include the word "balanced/ over balanced" diaphragm.

A true diaphragm has the least amount of parts and cannot be beat for reliability. A balanced / over balanced diaphragm increases pressure as you go deeper (same as a piston) a unbalanced diaphragm like the SP Mark 2 does not.

Click to expand...

I believe the SP MK2 only has 2 moving parts; tough to find a lower parts count than that. And, all 1st stages increase pressure with depth; they would not work otherwise. IP is always supplied as X over ambient; as ambient pressure increases with depth, so does total IP. I understand some "overbalanced" designs then further increase IP a little as depth increases, but it can never be too much, because the 2nd stage would then be subject to an increasing IP and possible freeflow at depth.

The "balanced vs. unbalanced" argument has very little to do with changes in depth; it's changes in supply pressure (tank) that affect unbalanced pistons differently, so IP drops when tank pressure gets low; it has nothing to do with depth. It's important to understand that a properly adjusted unbalanced piston like the MK2 will only show a significant IP drop, and consequently an increase in breathing effort, when the tank is REALLY low in pressure, like under 500PSI. On my MK2 I don't notice a thing until 300PSI. If you're at any depth with that amount of air, it's probably because you're not paying attention to your SPG and if the reg breathing a little harder reminds you that you're low on air, that's probably a good thing. BTW, as far as I know, there are no unbalanced diaphragm 1st stages currently on the market. I'm sure you meant "an unbalanced piston like the MK2".

I use a Dispahragm for my back gas and piston for deco. I use Diaphragm for my back gas because its good for Colder conditions and if you breath really hard. Your RMV Decreases when doing deco so I use a piston. Either are good but i would go for a Diaphragm. Plus they are easier to repair in the field.

I'm a flow thru piston fan, however Diaphrams have come a LONG way in the last few years and generally are better all around regs.

Diaphram.

I use an Apeks, which is an over balanced diaphram, and it can go deep and cold and would be considered a "top" regulator. I find it a very easy breather.

2006GTDiver:

I did some searching and didn't really find much…

Which is a better regulator design, piston or diaphragm? From what I'm seeing, piston looks to be the choice of most of the more top rated brands of regulators. What's the pros and con of each design? Does one or the other have an advantage in certain types of diving (IE, cold, deep, etc). I never really found a definitve answer...

I've tried out many regulators and did research and finally bought an Atomic B2 which has a balanced piston design. Great reg and the easiest breather I've used.

Click to expand...

I think that a environmentaly sealed Diaphram has a far less chance of freezing up during a cold/ice dive or exesively silty conditions. None of the moving parts are exposed to moisture or silt so less chance of regulator freezing up. I have the Oceanic CDX-5 1st stage along with the GT3 2nd stage that goes along with it and it is a terrific reg! I also have the Atomic B2 which is a terrific regulator too, I use both for my doubles set up.

In general, piston regs have fewer moving parts, but the diaphragm regs - by its inherent design - protect more of the internals from exposure to the water. Of course, with the inclusion of environmental protection packages, this advantage is pretty much negated. The precision of the parts of the piston is more important though, so for the DIY-er who plans to clean their own regs, this makes the diaphragm somewhat easier to clean.