Do I need a diaphragm reg?

[jiveturkey]

I have a scubapro mk25/s600 and love it. I recently moved back to Canada, bought a drysuit and have started diving in much colder water. I'm hoping to keep it going into the winter if I can. I'm just worried about my reg and freeflow. Haven't had any problems yet but I haven't had my reg in temps below 8 degrees either.

Should I buy a new diaphragm reg or just vary my technique for cold water diving?

I know nothing is a sure thing when it comes to freeflows. So, I'm not sure if it's really worth spending all that money on a new reg if the difference in reliability isn't that much.

Any opinions on this?

 

[Tamas]

While the diaphragm regulators are better for cold water diving, I understand the MK25 has a teflon coated interior that is designed to limit or stop freeflows. I would say try it, if it does freeze then look into a MK17 first stage maybe....if not then you are good.

A friend of mine dives with the same set-up as yours and to this day has had no problems with it freezing in cold water, but I guess everybody is different.

 

[DA Aquamaster]

Mileage seems to vary with some people having good luck with the Mk 25 in cold water and other people reall yhaving problems.

Good cold water technique is important. If you have problems you can always pick up just a Mk 17 first stage and then e-bay or maybe even trade in the Mk 25 first stage if the dealer is cooperative.

I recently bought two Mk 17 first stages and the price was right at $190 US for each of them.

 

[dbg40]

I have always had good technique, and never had a freeflow before I got my MK25.
then I had 3 in a row! ?? (38oF) Had to go to an Apeks DS4. bummer, im a die hard SP fan, but it seems that me and the 25 don't get along.

 

[jiveturkey]

Will I lose anything in the way of performance with the Mk17?

 

[DA Aquamaster]

In terms of raw flow rate, the MK 25 is tough to beat with a flow rate of 300 SCFM. In comparison the Mk 17 "only" has a flow rate of 177 SCFM.

But in reality anything more than about 110-125 SCFM is gravy and the Mk 17 has more than enough flow rate for any recreational, deep air or mixed gas technical application. It also has a very stable IP and no lag that I can detect in comparison to my Mk 20's and Mk 25.

My impression was that my second stage breathed better after the switch to a Mk 17, but to be honest that probably had a lot more to do with a fresh service and tune up of the second stages. At worst though, the Mk 17 breathes as good as the Mk 25 and I never have to worry about a freeze up even in 30 something degree F water.

I've used Sp regs since the early 80's including Mk 3's Mk 5's, Mk 10's, Mk 15's Mk 20's and Mk 25's and it is my opinion that the Mk 17 is overall the most capable and flexible regulator that Scubapro has ever produced when you look at a balance of performance, freeze protection and ease of maintanence.

 

[Greg Barlow]

In terms of raw flow rate, the MK 25 is tough to beat with a flow rate of 300 SCFM. In comparison the Mk 17 "only" has a flow rate of 177 SCFM.

But in reality anything more than about 110-125 SCFM is gravy and the Mk 17 has more than enough flow rate for any recreational, deep air or mixed gas technical application. It also has a very stable IP and no lag that I can detect in comparison to my Mk 20's and Mk 25.

As you and I have mentioned a number of times in the past, flow rates beyond around 150 scfm are really more of a moot point. Even the highest flowing second stages on the market cannot utilize approximately half the flow that a high quality balanced piston first stage can provide.

Me? I'll just keep on using my Mares and Apeks balanced diaphragm first stages. They more than meet my cave, wreck, and deep dive needs. 30 years of active cold water diving without one free flow has convinced me of the reliabilty of diaphragm first stages. None of my Mares first stages use environmental sealing, and I've never had a problem whether the water is 32 degrees or 82.

Greg Barlow