Piston or Diaphragm regulator?

[Akimbo]

Diaphragm first stages have gotten a little too good at low tank pressures. A distracted diver can breath a bottle down to 100 PSI before noticing abnormal resistance. A lot of pistons will produce perceptible resistance at 300 PSI, yet not be a hazard in less than narcosis ranges.

 

[captain]

Diaphragm first stages have gotten a little too good at low tank pressures. A distracted diver can breath a bottle down to 100 PSI before noticing abnormal resistance. A lot of pistons will produce perceptible resistance at 300 PSI, yet not be a hazard in less than narcosis ranges.

Many years ago there was a device that increased breathing resistance when tank pressure got to 300 psi and gave you a warning. It was called a J valve and it still works today in the age of SPG's. Most of today's divers aren't knowledgeable enough to realize it.
They don't monitor their SPG and run out when the J valve would have given them a warning. For all you redundancy freaks it would seem like a no brainer to use one.

 

[Stoy D Dabbs]

I use diaphragm 1st stages, Which is Scubapro MK16 and Apekx Regs.
I dive year round in lakes, In about February the water get most coldest as low as 36 deg. F.
At that temp. Piston Regs. will free flow.

 

[Akimbo]

... At that temp. Piston Regs. will free flow.

Not necessarily correct. The Aqualung Calypso, with an in-line piston first stage, meets the European Standards for cold water performance. I have used older versions in <30° water on air and HeO2 without incident. There are quite a number of diaphram first stages that manufacturers don't approve for cold water, let alone meet any standardized tests. It is not that simple.

 

[elan]

I use diaphragm 1st stages, Which is Scubapro MK16 and Apekx Regs.
I dive year round in lakes, In about February the water get most coldest as low as 36 deg. F.
At that temp. Piston Regs. will free flow.

Simply not true, My buddy has Sherwood Brut and we dove with him in 37F water. He never had any free flowing in that water. Sherwood Blizzard is another piston used for cold water. Temps below 32F on the surface as those in February require special handling on the surface.

 

[sladerer]

Piston - Atomic B2, waiting for my ST1. Wife will soon be diving the B2.

 

[Puffer Fish]

I feel strongly both ways...

Theorically the differences are:

1. Diaphragm

a. Is more reliable

b. Should be able to handle colder temperatures.

c. Over time, the diaphragm will stretch, resulting in poorer performance at low pressures.

2. Piston

a. More likely to fail (has a moving part, and wear surfaces.

b. Can open larger.

c. Does not have any issue with stretched out material.

Reality is that either can be made extremely well, and my two favorite regulators.. one is piston and one is a diaphragm...

 

[Stoy D Dabbs]

To Akimo and elan, Thank you for your correction and info.

I have dive with a Scubapro MK 25 Piston 1st Stage in 38 Deg. fresh water, there were times that explode with free flow. And since then I went to MK 16 I had not had free flow issue.
I got the MK 16 will befor MK 17 came out on the market, otherwise I would have gotten the
MK 17. However the 2nd stage that came with MK16 is another issue with it.

 

[Packhorse]

2 MK25's
2 MK20'
1 MK2
and a Apeks DS4 ( only cause I can convert it to being depth un compensated).

So I am a piston man!