Why Piston vs. Diaphragm???

[adamweldonjohnson]

Hey guys!

I'm going to be buying my first regulator, but I would like to buy right the first time (quality kinda guy). I've done some research into the different types of regulators, and I understand that diaphrams are fundamentally environmentally sealed, so here's my question: Why is it that the tech guys all prefer the piston regs over the diaphrams? (I.E. the Scubapro Mk25 over the Mk17).

Thanks guys,
Adam

 

[mtbrider]

Piston regs are very robust and tend not to have catastrophic failures. They do tend to require more maintenance.

In the unlikely scenario in which you need to swap regs underwater a piston reg will hold up better to water being blown through it.

 

[rjack321]

1) The hose routing on the mk25 is superb - for doubles
2) The mk25 breaths great
3) Unless you are in rediculously cold water or (highly contaminated) sealing doesn't do much for you.

Take what you need, sealing isn't needed (99% of the time). Sealing does not = better. If anything its just more complicated. Simple and robust are great attributes in tech regs.

Hey guys!

I'm going to be buying my first regulator, but I would like to buy right the first time (quality kinda guy). I've done some research into the different types of regulators, and I understand that diaphrams are fundamentally environmentally sealed, so here's my question: Why is it that the tech guys all prefer the piston regs over the diaphrams? (I.E. the Scubapro Mk25 over the Mk17).

Thanks guys,
Adam

 

[daniel f aleman]

Actually, there are dive prifiles where the MK17 is prefered, especially in cold and/or contaminated water. The piston is thought to be a simpler design allowing it to be repaired easier underwater, which is a feature necessity for many in the warm water tech community.

 

[DA Aquamaster]

To be honest, I like the hose routing offerred by the Mk 17 nearly as well and I prefer the lighter, smaller, excellent performing and basically cold water bullet proof Mk 17 to the Mk 25.

 

[Thalassamania]

Pistons have moving parts in contact with sea water, diaphrams do not. A "sealed" piston is every bit as good as a diaphram, though I tend to like diaphrams more.

 

[Hoyden]

Actually, there are dive prifiles where the MK17 is prefered, especially in cold and/or contaminated water. The piston is thought to be a simpler design allowing it to be repaired easier underwater, which is a feature necessity for many in the warm water tech community.

Exactly what repairs are being performed on first stages underwater? It is my understanding that those who prefer piston regs do so because they stand up to wet swaps (not a repair) better than diaphrams and tend to be less finickiy in general. As far as field repairs, pistons are more simple in design and nothing is easier to rebuild on a boat than a MK2, but a balanced piston like a MK25 is no easier to rebuild than a Apex/DR/Zeagle sealed first stage.


Jackie

 

[Thalassamania]

If I have an emergency that requires a wet swap I really don't care what the design of my regulator is, I'll swap it and clean it out later. IMHO that's a rather foolish critereon for regulator selection.

 

[The Chairman]

Reg reality 101

For 99.9% of all divers, trying to repair or change a reg underwater is probably a BAD idea. End the dive and switch to another reg ON THE SURFACE or wait to have your reg serviced by a competent technician. Consequently, I am not sure that underwater repairability is a feature you should be considering.

Both diaphragm and piston regs have proven themselves to be robust and reliable in 99.9% of normally encountered diving conditions. If you are planning to do some "extreme" diving, then other considerations should be considered. If you are following the manufacturers' recommendations for maintenance, the chance of catastrophic failure in either style of regulator is negligible.

A diaphragm will deteriorate over time and their adjustable nature reflects this tendency. The IP can be easily set on MOST of them with a hex or screw driver.

A piston reg requires more precision in manufacturing, especially in the chamber area. Corrosion or verdigris in the chamber area is also a concern, but sealing them will ameliorate the possibility of this happening. Most adjust their IP with the use of shims, but once set they usually hold their IP until the next service interval.

All regulators are subject to corrosion internally. It doesn't take much moisture at an elevated pressure to start the process. Any trash or corrosion on the high pressure seat will result in an IP creep and ultimately freeflows.

An often neglected issue for choosing a reg is hose routing. I prefer my hoses to exit the regulator at or near a right angle to the inlet. Some regulators have their hoses spaced radially around the regulator and this simply frustrates me.

But more important than ALL of that is how the reg feels to YOU. Dive it and see how you like the breathing charecteristics. Cracking effort, delivery volume and the tendency to over or under breathe all contribute to your comfort in the water. See if you can rent a set, or try your buddy's to see how you like it. BTW, most people will sing the praises of their regulators rather than point out it's shortcomings. It's human nature that wants everyone else to know that WE know how to pick the very best and therefore all other decisions must be flawed. Remember, your buddy won't be breathing your reg (unless he has crappy gas management skills): YOU WILL! Buy the reg for YOU and not for someone else.

 

[cerich]

Actually, there are dive prifiles where the MK17 is prefered, especially in cold and/or contaminated water. The piston is thought to be a simpler design allowing it to be repaired easier underwater, which is a feature necessity for many in the warm water tech community.

what are you smoking dude?!!!

Nobody does a first stage repair underwater.