balanced diaphragm vs. balanced piston

[mddolson]

This is a debate that's been around since I started diving in 1972 and won't likely end soon.
The ballanced piston is a good efficient design that minimises parts and cost, while delivering a high volume of air. The design however exposes both the high pressure oring, and the lower pressure oring to the water. If you dive in sandy silty water or id you're not as conciensious about rinsing the salt water out, then there is a higher risk of a malfunction. Sand, grit, dirt or salt crystals can score the shaft of the piston or orings and cause a leak. Having fewer parts the repairs are relativley simple but more frequent.

The balanced diaphram on the other hand has more parts, and seals, but these are isolated from the environment by the diaphram, so they are not subject to the same contamination as is the piston design. Anti-freeze or environmental kits are common which further isolate the balance spring and water chamber from the water with a layer of silicone oil and a rubber cover.

I own and use both, I am fond of the balanced diaphrams right now. But that's just my preference.

Mike D

 

[divrnr]

I own a Beuchat VX 10 Iceberg version and swear by it. It's a diaphram, I also have a Mares, a Dacor 960, a US Divers Conshelf Supreme, a ScubPro Air 1, a Posiedon Odin and I've tried out many other ScubaPros, and I still love the D400. Just find one that fits great and buy it. All the top manufacturers make a great product for rec diving.=-)

 

[Rockhound]

anyone who implies that piston type first stages are unsuitable for frequent use in saltwater is "full of it". There is no excuse for passing BAD INFORMATION.

I have a 25 yr. old Scubapro regulator that has made hundreds of dives in saltwater. It was regularly serviced and I never recall any problems with it beyond some carbon contamination from bad air in Mexico (cough, cough) and a later need to upgrade the spring when tanks went from the old 2750psi steel standard to 3000 psi. (it developed a harmonic, a "waaaannggg" when the pressure was above 2900 psi. This was corrected by my dealer, who also upgraded the yoke. There was no charge for this, btw.).

I moved over to an oceanic Delta for no other reason than it was "new" and I wanted some new gear. This rig also uses a piston 1st stage and I have used it for hundreds of mostly saltwater dives with no problems. It is a great, easy breathing regulator.

With the Lifetime Warrantee on parts still in effect, I have no fears about having to replace a piston, however, I expect that no replacement will ever be necessary. (I don't think Ocean offers the Lifetime part warranty anymore, do they?)

I have no preference for one type of 1st stage over the other, however, because I have such good service with my piston stages, I am likely to stay with them.

The key , as someone pointed out, is good and regular service to your entire rig. As for SPro's marketing policies, I have some legit criticisms, but I have no criticisms of their equipment.

My advice would be to buy the best breathing and most serviceable regulator you can afford. If you think the SP breathes better, fits better and is more comfortable, buy it. If the Mares doesn't breathe as well, or if you are less comfortable with it, then your decision is made. If they are equal in your mind, then as that other poster suggested, "Go with the Force". I understand Mares makes good gear, too.

I don' t know much about Mares, never having dived one, but I do know that my ScubaPro and Oceanic regulators have outbreathed or equalled every other setup I have tried. I don't think you would go wrong with either one.

 

[JamesK]

Originally posted by divrnr
I own a Beuchat VX 10 Iceberg version and swear by it.

I agree! I love my VX10. I use it for all of my OW and in caves. However, I use love my ScubaPro. Both breath excellent. I have had no problems out of either of them. I would recommend either in a heartbeat.

This is a never ending debate.

 

[DivingDoc]

Well, I made up my mind -- ScubaPro regs all around. I got an MK25 S600, my son got an MK25 G250HP (not sure which is better -- some people think that the G250 was the best reg ever made by SP. My husband got a used MK20 G500, which I tried in the water and it breaths great -- only 50 dives on it.

My son and I both tried out a Mares Abyss in the pool and found it very uncomfortable because of it's weight. Also, I thought even the used SP breathed better -- at least at pool depths.

Now for the computer....

 

[metridium]

Originally posted by DivingDoc
my son got an MK25 G250HP (not sure which is better -- some people think that the G250 was the best reg ever made by SP.

That may be true, but the G250HP is NOT the same reg. In fact, I've had one SP dealer warn me away from the HP when I was looking for a second G250.

 

[redacted]

Your stages are basically all the same on the inside. One each 1st stage and 2nd stage annual service kit will cover all 3 of you when you travel. I think you will be quite happy with your choices.

 

[DivingDoc]

Oh -- theres a difference? What's the difference?

 

[metridium]

Originally posted by DivingDoc
Oh -- theres a difference? What's the difference?

The guy wasn't overtly trying to steer me toward any other regs, but did indicate that the HP was not the equal of the G250 I already had. Wish I'd followed up on it so I could answer your question, but I didn't. Sorry.

Hopefully one of the experts here will step forward....

 

[redacted]

The 250 & 250hp do take different annual service kits so there must be some engineering difference even though they are basically the same design. The S600, G500, and G250HP all share the same service kits so their only difference may the material used to construct the barrel as well as the outer appearence. I believe the S600 uses some new composite that was not used in the G500. It can be upgraded but I doubt if it's worth the $$$. I'm guessing the G250HP is the same barrel and innards as the S600 with a different balance knob mechanism to fit the larger reg body. Just a guess as I do not have the schematics for the newer regs. In any case, any difference in their performance should be a matter of wear & tuning rathe than model.