View Full Version : Diaphragm Vs. Piston Regs?

09-22-2007, 18:48
What's the difference between a diaphragm regulator and a piston regulator and which one would you prefer?

09-22-2007, 23:07
I prefer a diaphragm because I dive a lot of cold waters. The concept it that the piston doesn't tolerate the contraction of parts due to cold. Also the formation of "ice" inside the first stage due to the water temps as well as the movement of the air. Not sure how to explain the air movement causing "ice" formation. At any rate the piston freezes in position or at least gets harder t o move.
If I am thinking right it is suggested anything below 50ish degree water, dive a diaphragm.
Add to or correct anything that I typed, I'm not an expert on this one.

A sealed reg also isn't a bad idea even if you are diving in the tropics.

09-22-2007, 23:17
I'm assuming the diaphragm is sort of like a flap and the piston has actual mechanical parts? Please correct me if I'm wrong. I'm totally ignorant in the regulator field...

09-22-2007, 23:38
I think it is safe to say...you have the general idea. Might check around and see if you can find a cut away view of a reg, it makes more sense then.

09-23-2007, 09:16
Google is your friend.

A search on "Scuba regulators how it works" gets this as 1st hit.


As well as other interesting looking hits.

09-23-2007, 09:58
Thanks awap. I was too busy with other things to Google.

09-23-2007, 12:40
Yeah, thanks Awap, that helps a bunch, especially that little flash video.

10-01-2007, 15:06
When in doubt, Wikipedia (http://en.wikipedia.org/wiki/Diving_regulator) is your friend. :smiley20:

Wikipedia actually gets me in trouble. I'll go read one article, then I have to read the 20 links to other articles, so forth and so on. :smiley36:

10-01-2007, 15:21
I was just in Lubbock for Family Weekend (daughter goes to Tech).

Saw a SCUBA shop on Indiana. Where do you guys dive out there?

10-02-2007, 21:21
I have both a piston and Diaphragm reg. Both work great and honestly, I can't tell any difference. I dive mostly in topical waters so freezing has not been a concern for me.

10-03-2007, 01:00
Well let's start that the piston style regulators work on ambient pressure from the water on the outside. If you look at a piston style regulator for example a Scubapro MK 2 or MK 25 you can see the open holes around the body of the first stage. If I recall correctly these types of first stages need a enviromental kit put on for cold water diving. I've heard mixed results for CWD with these types of regs. Some I'm told really have freeflowing problems while others have good luck.

Now the Diaphram style regulators uses a rubber or silicone diaphram that closes the first stage completely from the outside enviroment. And again the ambient pressure is working on the diaphram and not directly on the inside parts. All components are safe from cold water, and other contaminents from the outside. Now, their are diaphram regulators that require the CWD kit for performance in cold water. Example is like the Mares Proton Metal or Metal Extreme (which already has one). You can see the difference when you click on one and then other in Scuba Toys store.

I personally use a diaphram style regulator and love the system.

Hopefully this helps.