Mk25/s600 and s555... right for cave?

[SteveAD]

I wouldn't hesitate to step all the way down to a mk 2 r190 for a deco reg. High performance regs are necessary at depth where each breath is the equivalent of many surface breaths or where air sharing thru a single first stage will require a greater than normal airflow, but a deco reg rarely has more than a single second stage on it, so air sharing is not an issue and with a high fo2 deco gas you'd better not be using it where one diver might overbreathe a reg. The only real concerns on a deco reg are reliablility and o2 compatiblity.

The argument could be made though to have the same reg at all positions to minimize required spare parts and maximize interchangeability.

dschonbrun mentioned the 555 might be overkill for an octo, the mk25 is certainly overkill for a deco reg, but when it concerns my ability to breathe, I REALLY LIKE overkill.

 

[Trixxie]

every time I get my mind set on double MK25/600 someone comes along and says "The MK17's are environmentally sealed" then someone else says "MK25's are the top of the line and are better for hose configuration".

I don't plan on diving extremely cold or polluted water. Caribbean, quarries, local lakes, FL springs for cavern and maybe one day full cave. seems like most who have posted on this thread have the 25/600 or 555 as their set up and not the MK17.

my cavern inst has MK16 the other folks in the shop who have done cave that are now moving on the adv nitrox all have MK17/555. they keep trying to talk me out of the MK25 to get the 17.

I know that both are great regs, sometimes I just feel like throwing up my hands and saying "forget it, I am just going to keep my 13 year old sherwood" but I know it's time to upgrade.... but to WHAT????

25/600? 17/600? help!

 

[solensdotter]

Thanks, stevead! Like you, I am a fan of overkill. After all, it's life support! On the other hand, at some point the dollar signs talk, too....

It's an AL-40, so it's life as a deco bottle will be for high fo2. However, since the tank will also be used as a pony/bail-out when I'm not diving doubles, it is unlikely - though possible - that it will be used at depth...

Got the wing, working on the tanks. I thought that I was making progress, but this is obviously just the beginning!

 

[bdorough]

Mauigal, the difference is the MK17 is a diaphragm 1st stage and the MK25 is a piston 1st stage. I have dived both and like them both. I stayed with the MK25 because I have three of them and did not want to bring the MK17 into the mix. If you are buying new and do not have either one, I would say go with what you know and/or comfortable with. Most people today buy diaphragm as they are easier to tune (MK17). Some of us old farts just like pistons.

 

[bdorough]

I know this is a little out of this thread, but I like the OMS Workhorse O2 clean for my deco reg. It's unbalanced, reliable, and inexpensive (you can find them new for 150 - 160). Even though unbalanced, it works fine at 20 and 30 feet. Also, it come O2 clean out of the box.

 

[SteveAD]

Mauigal, the difference is the MK17 is a diaphragm 1st stage and the MK25 is a piston 1st stage. I have dived both and like them both. I stayed with the MK25 because I have three of them and did not want to bring the MK17 into the mix. If you are buying new and do not have either one, I would say go with what you know and/or comfortable with. Most people today buy diaphragm as they are easier to tune (MK17). Some of us old farts just like pistons.

No longer true. The primary difference between the mk20 and the mk25 is that the mk25 has an externally adjustable intermediate pressure. In other words the mk 25 is a piston reg that is as easy to tune as any diaphragm.

 

[DeepSeaExplorer]

Thanks, stevead! Like you, I am a fan of overkill. After all, it's life support! On the other hand, at some point the dollar signs talk, too....

It's an AL-40, so it's life as a deco bottle will be for high fo2. However, since the tank will also be used as a pony/bail-out when I'm not diving doubles, it is unlikely - though possible - that it will be used at depth...

Got the wing, working on the tanks. I thought that I was making progress, but this is obviously just the beginning!

I have mixture of 5 sets of MK20s, 25s for 1st stages and 550, 500, and 390s for seconds. They all work for just about any type of diving be it deep or hard swimming.

Some will tell you that for comfort reasons you need your best reg on your deco bottle since you will be breathing it for a significant portion of the dive. However, you don't need that level of performance from a deco reg, especially an O2 reg.

As far as other uses, I use the MK25/390 for stages. It has no problem delivering gas while swimming hard against the flow at Ginnie with a lot of drag: dry suit, double 104s, deco and stage bottles.