Question re: diaphragm vs. piston first stage

[berk]

I tend to prefer diaphram regs due to the ability to adjust the IP without dissambling the reg.

Never thought of that; that's a good one.

 

[theduckguru]

I use a piston 1st stage. I find that I am more dedicated to post dive soaking of the reg than I would be with a diaphram 1st stage because I know I have salt and other contanimants inside the reg. If you are willing to give the reg this added care, I don't see where its a big difference.

ScubaPro makes the following claim with their piston 1st stage,


"Air balanced flow-through piston - First stages with air balanced pistons deliver significantly more air to the second stage than any other first stage, while their performance is totally unaffected by the changing tank pressure. A balanced piston allows the use of lighter and more sensitive components, resulting in ultra fast breathing response, instant delivery of air on demand, and extra high air flow, especially in low tank pressure ranges. The tired diver benefits from a smoother breathing regulator during the ascent or deco stop. Balanced piston first stages are the first choice of demanding sport divers and professionals. A balanced piston performs equally in warm and cold water environments".

 

[Thalassamania]

You got paid for diving. Woe is me...

No ... I got paid for administering.

 

[Belce]

I live where I live and use a MK25/A700

Sorry to disappoint, but no trouble

There are alot of folk that will say it can't work or won't work or this doesn't push you to brands I'm paid to

But the Mk25 Scubapro 1st stage will work in any situation you put it in for diving

 

[Thalassamania]

No one is saying that a Mk25 can't work or won't work, just that for a new item purchase there are better choices, for a number of reasons.

 

[taucherguy]

My first reg was the Atomic B2 (in 1999) and for my buddy Oceanic Delta 3. We did share air to try out eachothers regs and neither I or my buddy could tell any difference. Fast forward to now. I use Hog and am happy with it.
But would I take a MK25/700 setup for offering my opinion for free? You betcha

No one is saying that a Mk25 can't work or won't work, just that for a new item purchase there are better choices, for a number of reasons.

 

[herman]

......
ScubaPro makes the following claim with their piston 1st stage,


"Air balanced flow-through piston - First stages with air balanced pistons deliver significantly more air to the second stage than any other first stage, while their performance is totally unaffected by the changing tank pressure. A balanced piston allows the use of lighter and more sensitive components, resulting in ultra fast breathing response, instant delivery of air on demand, and extra high air flow, especially in low tank pressure ranges. The tired diver benefits from a smoother breathing regulator during the ascent or deco stop. Balanced piston first stages are the first choice of demanding sport divers and professionals. A balanced piston performs equally in warm and cold water environments".

This mostly sales hype with some half truths.
"First stages with air balanced pistons deliver significantly more air to the second stage than any other first stage" Sure their top of the line first stages flow more gas than a diaphram or flow by piston regs....trouble is second stage is the limiting factor in the system so as long as the first stage can keep up with 2 second stages and a couple of heavy breathing divers it really does not matter how much gas it can flow and all modern first stages (and most vintage) are capable of the needed flow.

Ultra fast breathing responce??? Please, the gas in the hoses and reg chambers act as surge suppressors smoothing out the gas flow so even if it has an "ultra fast breathing response, instant delivery of air", the air spaces in the rest of the reg components mask it. IF you have it attached directly to a machine you can see the difference but a diver breathing off the second stage can't.

SP makes fine regs but you have to learn to seperate the sales hype and half truths from the real world facts.

 

[halocline]

One nice thing about the SP balanced pistons (well, most of them, anyway) is that they are super stable with regards to IP. My MK5s go for years without a hint of creep, in fact, I don't think I've ever seen one creep once I rebuilt it initially. I bought my MK15 at least 5 years ago, and it's on the same seat that went in it when I bought it. I don't use it very much, but I use the MK5s weekly. I've seen MK25s with the composite piston go hundreds of dives with no sign of any IP creep or drift. It is an extremely successful and durable design, considering the number of times that valve opens and closes and how precisely it responds.

Where SP went wrong IMO with the MK25 was by not continuing the totally proven SPEC cold water system, where you pack the ambient chamber with grease. In fact, with the development of the PTFE greases like Christolube, packing the ambient chamber makes even more sense. The only "problem" is that its more work and a little more expense to rebuild. But, with a packed ambient chamber, these regs could go even longer without service.

I don't live around cold water, but if I did, I'd be perfectly happy using my packed MK10s with balanced/adjustables. I'm certain that's as freeze-resistant as any current reg.

 

[cool_hardware52]

I tend to prefer diaphram regs due to the ability to adjust the IP without dissambling the reg.

This is not unique to diaphram regs. One can adjust the IP on a MK25 via an externally accessible preload screw.

Tobin

 

[Couv]

....snip... I always find pistons to be a little more crisp when they open and close, almost like a snap to it.

Whilst breathing off the second stage, I have yet to be able to tell the difference in performance between a piston vs. a diaphragm first stage. Could you explain this statement please?

couv