scubapro first stage differences?

[oversea]

Can anyone tell me what the difference is between the mk16 and mk25 first stages (besides piston vs diapram). I currently have a mk25/s600 and am looking to buy a first stage for my R390 as I am am setting up doubles. Does the mk 16 breathe well? How about compared to the MK25? Any opinions would be appreciated.
Thanks

 

[halocline]

You could search DA aquamaster's postings on this; I remember one that described in detail scubapro 1st stages. I do know that the mk16 is pretty highly thought of for a mid price reg, never heard anyone complain about it. Given the fact that most buyers are using their regs for recreational diving and maybe occasional tech stuff, I'm kind of surprised you don't hear more about the mk16. The LDS where I bought my mk2 only stocked the mk25, as they said with an up turned nose "our customers want the top of line reg." I'm absolutely certain that the salesmen at this store would be completely unable to tell the difference in water between the mk16 and mk25. I also imagine that this attitude is not that uncommon.

 

[oversea]

I also imagine that this attitude is not that uncommon.

Absolutely. this attitude is what is steering me away from Scubapro. If I did not already have it, I would'nt buy it.

 

[halocline]

Absolutely. this attitude is what is steering me away from Scubapro. If I did not already have it, I would'nt buy it.

I don't think the snob-esque attitude is a scubapro fault, just a function of that dive shop's bizarre approach to sales. I bought the lowly mk 2 because my instructor, with many years' experience, recommended it, and I've been very happy with it. The other salesmen at the dive shop gave me this doom and gloom scenario about the horrors of diving with an unbalanced reg.

Anyhow, this is dangerously close to hijacking the thread; sorry.

 

[DA Aquamaster]

The Mk 16 has a flow rate of about 175 SCFM while the Mk 25 has a flow rate of 300 SCFM. So the Mk 25 has almost twice the performance of the Mk 16. But I'd challenge any diver to tell the difference between a Mk 16 and Mk 25 in a blind test.

In the real world, 150 SCFM is all you need in even the most demanding diving situation. If you are deep enough for the Mk 16's 175 SCFM flow rate to be inadequate, you are deep enough that you have long since switched to helium mixes which slip through regs better anyway, making a reg capable of flowing 175 SCFM of air more than adequate for well over 175 SCFM of trimix.

One advantage of the Mk 16, is that I have never seen one freeze up even in water as cold as 33 degrees. I cannot say the same for the Mk 25 which can encounter problems freezing up in water colder than about 40 degrees.

SP has a marketing philosophy that promotes the MK 2 R190 and MK 2 R390 as it's entry level regs, the Mk 16 R390 and Mk 16 S550 as it's intermediate level regs and the Mk 25 with the S550, G250, S600 or X650 as its top end regs. Consequently SP packages first and second stage combinations in this manner and encourages sales to entry level, intermediate and advanced level divers accordingly with the goal of getting 3 sales to a diver over the course of their career. If you stick with their packaging options, you are also essentially forced to go with a more expensive first stage to get a balanced and adjustable second stage and this maximizes SP's profits.

From that perspective, some dealers may feel they are doing a diver a favor by selling a Mk 25 with whatever second stage to them initally under the "if you buy the best, you only have to buy once" philosophy. SP sales reps are not big fans of that approach either for obvious reasons.

The truth is though that SP will sell any first stage with any second stage, all the dealer has to do is order them that way. You pay slightly more by losing a package discount, but you can still get very practical and excellent performing combinations like the Mk 16 G250 or Mk 16 S600 or Mk 16 X650 for far less than you could get the same second stages packaged with a Mk 25.

So if you are diving cold water or if you prefer the Mk 16 first stage and do not want to the non adjustable S550 or the unbalanced R390 second stage, ask your dealer to get you specifically what you want. And don't take no for an answer.

 

[Life-Is-Good-Diver]

What about enviromentley sealed first stage's on the SP line for cave and wreck diving?

 

[cnctina]

I have a mk15-bal adj. and a mk2-380 and I can't really tell the difference. I actually think my air 2 breathes the best. I put a 550 cover on my 380 so it looks like I spent the big bucks. The mk2-380 is much easier to service, simple and dependable.

 

[oversea]

One advantage of the Mk 16, is that I have never seen one freeze up even in water as cold as 33 degrees. I cannot say the same for the Mk 25 which can encounter problems freezing up in water colder than about 40 degrees.

You hit it there. The reason I was asking is because I currently have a mk25/s600 primary reg and a standard r390 octo (not the yellow one). I am looking to begin using doubles and need a first stage. I have heard the mk25 (because of the piston design) has the possibility of freezing. The mk16 is the diaphram design and have heard elsewhere it is much more resilient to freezing. So, my thought was to use the mk25/s600 as my primary and the mk16/r390 as my backup. I felt this gives me a great breathing reg as my primary (which I already own) and a good breathing backup that is a bit more tolerant to the cold should I need it. I mostly dive up in the northeast. My first dive this year at depth was about 35 degrees. My reg made me a bit nervous although I had no problems.

 

[DA Aquamaster]

There are several factors that contribute to MK 25 freezeups including intermediate pressure (lower IP around 120-125 is preferred), tank service pressure (lower is better), SAC rate, and cold water technique (not inhaling and inflating dry suit at the same time, not testing reg on the surface, etc.).

Just one of those factors can make a difference. I and an equally cold water savvy and low SAC rated buddy did 5 dives with Mk 25's in 35 degree water on the same weekend. He froze up on 4 of the 5 dives while I had no problems. The only difference was that he was using 3000 psi tanks and I had 2400 psi steel tanks. He switched to a MK 16 first stage and has not had a problem since.

Both the Mk 16 and Mk 2 do exceptionally well in cold water and divers around here frequently use them ice diving. Scubpro has developed a fully sealed diaphragm first stage, the Mk 17, probably in response to divers who think a fully sealed first stage is important. I am waiting until I see one and dive one to decide if it is an improvement over the Mk 16. On the one hand the Mk 16 has a proven record of cold water performance and is a sure thing. On the other hand, the Mk 17 looks very good on paper and the fully sealed environmental chamber is a theoretical advantage, but the ultimate question will be how prone that seal is to failure over the course of a few hundred dives.

A Mk 16/R390 makes sense as a backup. The R390 is a downstream second stage design and is very simple and reliable, making it a good choice for that application.

 

[Wayward Son]

I'm curious if you know the specs on the older Mk5 regulators? I still dive one -routinely, it's my only reg- that I bought new in 1978. It is the higher PSI rated yoke, not the older 2400 yoke.

One of these days I'll prolly upgrade to a new reg, but I've always been happy with the way this one breathes.