Is SP Mk2+ a cold water 1st stage

[AquaNSun]

There're indeed many choices when it comes to regulators and personal preferences differ. Just like computers and it is impossible to keep up with all the latest technologies.

The point is - it all depends on the type of diving you're doing and what are your priority. I think everybody knows that the Mk2 IS an entry level regulator and is recommended for use in recreational limit. For me, and most people, I like to know my reg just like my girlfriend/wife
inside out. If you "really" know your equipment limitations and have tested it in many different dives, that's the kind of confidence you'll develope with your equipment. In that case you'll not feel you're taking any chances. As confirmed with many reports and divers' experience on this board, the Mk2 is capable of around 130ft and cold water in the 40ish range. So, that is the capability of the Mk2 and in my opinion is a darn good one for recreational diving in addition to its simplicity and reliability. There's always pros and cons in everything. A Mk25 is great but can't
compare to the simplicity of a Mk2 and there are people who like simplicity. The Mk2 is out there
for so many years for a reason.

There is no best reg in the world. Everything is relative and most importantly if you know your reg and happy with it - that is what it counts.

Many refer the Mk2 to 'low end' reg and I think that is misleading as new divers would have the impressions that they will fail or break easily. Or the impression that latest technology is always the best.

 

[halocline]

To say that the MK2 is not appropriate for deep diving is really misleading. It has a flow rate of just under 100SCFM, which is the equivalent of emptying and AL80 in under one minute. I've used mine down to 130ft and there's absolutely no problem. The highest end 2nd stages under full purge maybe flow 50-60CFM. Tank valves are the bottleneck in flow rates in a typical scuba set up.

One reason the MK2 does not have the same reputation for ease of breathing is because it's usually paired with an unbalanced, lower performance 2nd stage. I did a comparison once with the same 2nd stage (G250) on my MK2 and my MK15, on subsequent dives. There was very little, if any, noticeable difference.

Now, if you were REALLY deep, like say 180 ft, and two divers were hyperventilating off of one MK2, AND tank pressure was 500PSI or below, then you might start to exceed the capacity of the reg. But then in that situation you'd have some other big problems, wouldn't you?

It's easy to lose perspective on regulator performance with the incessant marketing and comparisons of various high end regs. The truth is that they all work far better than we actually need for diving. Just a few decades ago, professional divers were routinely making extreme dives, far beyond current recreational standards, with regulators that most OW students would not take in a pool today. (Not that those regs were bad, in fact some were quite good)

 

[DA Aquamaster]

I had a similar discussion today re: the Mk 17 and Mk 25. The Mk 25 will flow 330 SCFM and SP most recently rated the Mk 17 at 220 SCFM. The reality is that there just aren't any valves out there that will flow 220 SCFM let alone 330 SCFM, so the difference is a moot issue.

If you open the valve wide open on an AL 80, it will take a few minutes minimum to drain. Obviously way less than 100 SCFM. Now, to be fair, when you just open the valve, the pressure is well below tank pressure in much of the valve passage. In contrast when connected to a reg, you may cause the pressure drop to occur farther along so you may get more flow rate with a reg than without one on the valve. But in any case, the valve will still be the limiting factor not the first stage, no matter how many second stages you attack.

You have to go well below 130' to "out breathe" a Mk 2.

 

[halocline]

DA, if I'm not mistaken, reg manufacturers test the flow rates of their regs with all LP ports wide open and the reg connected to a high flow, constant 3000 PSI source, correct?