Piston vs. Diaphragm

[shrwdtech]

ew1usnr once bubbled...
I don't understand the Sherwood Tech's comment "And with the exception of a very few 1st stages on the market, they BOTH allow water inside them in order to balance for the increased pressure on the unit at depth."

On a diaphragm reg, water will get "inside" as far as the outer surface of the diaphram. To me, that's still the outside. What's on inside of the diaphragm is the inside of the regulator. The diaphragm seals the outside away from the inside. On a piston regulator, water comes in contact with the metal (usually brass) cylinder walls that the piston slides up and down against, as well as the top of the piston.

You are correct, and I apologize for not being a bit more clear in my answer. Water enters both regs in as far as either the surface of the piston, or the surface of the diaphragm.
Where the water hits is very close to the same in both systems, with the exception of a very small surface inside the body or cap of the piston designed reg. Either way water, be it dirty, cold, yucky or chlorinated never hits any of your air supply. I know nobody claimed that... just tossing that in as I overheard a local sales person say that recently.

Over all, in servicing of regs, I've never found one to be any cleaner than another when I take them apart for service. On an average, each needs to be cleaned and is in about the same shape by the time the consumer gets them serviced. It's all in how well we take care of our toys, for the most part.

 

[Raven C]

Which do you prefer and why?

This is not for just polling. I am educating myself. I may not have looked at your point of view. R

 

[Charlie99]

Apeks diaphram regs, "because George says so".

It used to be ScubaPro piston regs "because George said so".

 

[MechDiver]

If you do a search in forums, I imagine you'll get a few hundred hits on this subject.

 

[Diver0001]

RavenC once bubbled...
Which do you prefer and why?

This is not for just polling. I am educating myself. I may not have looked at your point of view. R

DEpends on how cold the water is. As a general rule I would recommend a diaphragm in cold water becuase most pistons let water into the 1st stage to balance it and that water could theorectially freeze. There are exceptions to that too, like the sherwood regs.

R..

 

[ElectricZombie]

All my first stages are ScubaPro pistons. I don't dive in cold water so, a piston reg works great for me. I am planning to pick up a few diaphram regs (probably ScubaPro Mk16s) to use as primaries or on deco/stage bottles. Either a piston or diaphram reg is fine if you are doing warm water stuff.

 

[richhagelin]

I'm getting back into diving after 20+ years and I am researching regulators. What is the difference between balanced and unbalanced? What are the pros and cons?

I've heard about a piston, what else is there? Is it first stage? What are advantages/disadvantages?

Thanks,

Rich

 

[redacted]

http://diver.net/capture/musac.cs.man.ac.uk/regs/regs.htm

Unfortunately, the diagramed 1st is a diaphram rather than a piston. But it & it's additional links talk about balanced & unbalanced. One thing I didn't see mentioned is that a balanced 1st is usually capable of delivering a higher volume of gas since the orifice at the HP seat can be larger. Balanced designs are often associated with higher performance.

 

[paulwlee]

Balanced regulators (here it usually refers to whether the first stage is balanced or not) maintain the same IP (intermediate pressure) regardless of the tank pressure until the tank pressure becomes close to the IP. With unbalanced regulators, the IP changes slightly with the tank pressure. For downstream designs it decreases as air is used up, for upstream designs it increases.

Generally, they say balanced regulators work better. However, it is also said that modern unbalanced regulators have become really good and work almost as well as balanced regulators for any recreational diving applications.

Unbalanced regulators are cheaper and slightly more simpler.

There are both balanced and unbalanced pistons, the unbalanced pistons being the low end model for many manufacturers.

The other type of regulator is the diaphragm regulator. All diaphragm regulators are balanced.

With diaphragm regulators, there is no water contact at all with the internals of the regulator, so is good for contaminated environments or ice (or very cold water) diving.
Piston regulators are simpler, and are thus easier to work on.
Performancewise, there isn't really an advantage to either.
Some claim that diaphragms are more responsive and pistons provide more airflow, but it's not clear whether it's true or makes any difference.

Most regulators from major manufacturers work well, be it high-end or low. Take a look at the regulator reviews at scubadiving.com if you haven't already.

 

[ScubaRon]

Many people believe that piston 1st stages are more prone to freeze-ups in very cold (<50F) water.

I don't know if this is true, but after some research on this and other forums and the Web I found plenty of indications that this might be true. So I figured better safe than sorry and ordered a diaphram regulator.

Something to consider if you plan on doing cold water diving.
ScubaRon