Is the mk25 superior to the mk17???

[adm3745]

mattboay is right. Even with 2 panicked divers at 190 feet say, theres gonna be plenty of air from both regs. If you check out my link, DA aquamaster said some good points. Caving or dirty water can damage the pistons more than a diaphram. My mk25 works just the same in dirty, silty water, but I clean it extra well both pressurized an unpressurized. If you find yourself in those conditions more often go for the Mk17.

 

[gmudiver]

What's the difference between 300SCFM and 175SCFM? It's the ability to theoretically drain an AL80 in 15.4 seconds vs 26.4 seconds.

Since we all know that opening a tank valve on an AL80 will not drain the tank in anywhere near that amount of time, it's clear that the flow rate on both regs far exceeds that of the tank valve. So someone tell me how a MK25 "breathes better" due to the higher flow.

I'm a big fan of SP balanced piston regs, I have a bunch of them, but the flow rate is just not that important. What is important IMO is the great IP stability and lightning fast lock up they have over the long haul.

Sorry I'm kind if new at this, could you explain what you mean by IP stability and fast lock up?

 

[NJDiver07866]

Have both.....had one bout of icing on the Mk25 but was solved with just a shutdown for a few minutes and then just cycled the tank valve open and it cleared up. Ever since that no issues. Water temp 43+. I notice when I service the reg if I don't dash the piston with fresh water after use you can get some shmegma build up, but easily solved with a cleaning/service.

MK17 looks brand new each time I open it up. Only beef is that the plastic cover that protects the outer diaphragm can fall off if you knock it good or squeeze yourself into tight spots.. so just keep a stock of them.

 

[walke121]

mattboay is right. Even with 2 panicked divers at 190 feet say, theres gonna be plenty of air from both regs. If you check out my link, DA aquamaster said some good points. Caving or dirty water can damage the pistons more than a diaphram. My mk25 works just the same in dirty, silty water, but I clean it extra well both pressurized an unpressurized. If you find yourself in those conditions more often go for the Mk17.

I agree I was just giving the stats. Both regs are like owning a Ferrari, there is more performance than you will ever need but people pay to have the best.

 

[DA Aquamaster]

I switched from Mk 25's to Mk 17's for the reasons indicated in the linked post. The cold water tipping point for the Mk 25 seems to be about 45 degrees F - below that freeflows are too common for my liking on deep technical dives. The Mk 17 on the other hand is bullet proof in cold water and is preferrable in sandy and silty conditions due to the sealed design. I still use Balanced pistons for my stage and deco regs, and every year I clean lots of crap out of them while my Mk 17 back gas regs look new inside at every service. That gives me piece of mind a half mile back in a cave.

Asd indicated previously, the difference in flow rates is a moot issue as 175 SCFM is more than enough and 300 SCFM is massive overkill. Sort of like having enough nukes to kill every living thing on the planet - past that point, do more nukes really make a difference?

In terms of hose routing, the crossed hosed approach used with Mk 25's and doubles works, but it is by no means the ideal that it has come to be perceived as being. I much prefer the Mk 17 as the hoses route straight down off each first stage and the results are much cleaner. On a single tank, the Mk 25 is superior in terms of hose routing.

The IP resopnse of the Mk 17 is superb with a very rapid IP swing at the end of the inhalation and an IP drop of less than 10 psi. In other words, you can't tell the difference between it and a Mk 25 with an IP gauge and consequently neither can a second stage. I know when I switched I was using very finely tuned D400's (0.5" of water inhalation effort) and with a Mk 25 on one poist and a Mk 17 on the other, I could not tell which one I was breathing from as the performance on the test bench and in the water was identical.

The idea that the Mk 25 breathes better is just SP marketing hype to keep the Mk 25 positioned as their "premier" reg when in fact it isn't as the Mk 17 offers a wider range of suitable temperatures, is easier to maintain in dirty water or salt water, and offers better hose routing in doubles. The swivel port equipped Mk 19 (a Mk 19 with a swivel cap like the Mk 25) would make this statement true for singles as well if SP sold the MK 19 in th US.

 

[gmudiver]

mattboay is right. Even with 2 panicked divers at 190 feet say, theres gonna be plenty of air from both regs. If you check out my link, DA aquamaster said some good points. Caving or dirty water can damage the pistons more than a diaphram. My mk25 works just the same in dirty, silty water, but I clean it extra well both pressurized an unpressurized. If you find yourself in those conditions more often go for the Mk17.

I checked out that link to the other thread, thanks for posting it!

Aquamaster thanks for the great info, and thank you to everyone else as well!
Evryone has made great points for both regs, I think I am leaning towards the mk17 at the moment, if the flow it has is above normal as it is, and it being sealed seem to make it a great all around reg. Not by any means to put down the mk25 it sounds awesome as well. I just like the fact the mk17 is sealed. I still got some time to decide however so the more info I can get the better!

Also if someone could explain what the "IP" of a reg is, I'm still not clear on that. Thanks!!

 

[Belce]

IP is short for intermediate pressure, the 1st stage should deliver air at a certain pressure, 140 psi is normal, it can vary some, the second stage steps that down to current psi for your depth.

I am very much interested in hearing how a 4 port non swivel 1st stage routes hoses better than 5 port swivel 1st stage does, even willing to view diagrams... really

 

[tregrrr]

IP is short for intermediate pressure, the 1st stage should deliver air at a certain pressure, 140 psi is normal, it can vary some, the second stage steps that down to current psi for your depth.

I am very much interested in hearing how a 4 port non swivel 1st stage routes hoses better than 5 port swivel 1st stage does, even willing to view diagrams... really

just a note to the new to terminology diver who asked for this clarification...

with both of the SP regs we are discussing, they are both balance regulators which means they take local ambient pressure into account and as such the 140psi noted above would be 140psi ABOVE your current depth's associated pressure.

A reg like the Mk 2 is unbalanced meaning that the 140psi Intermediary Pressure is just that, 140 psi, regardless of how deep you are.

when you get to 120', which is 4atmospheres more pressure than at the surface, that means your local pressure is 60psi (using 15psi/atm for sake of mental math) and thus at this depth with say a Mk2 you would only have the equivalent of 80psi IM... enough to still breathe it fine, but still a noticeable drop, compared to the balanced ones which would deliver 140psi + 60psi so that it still breathes the same as on the surface...

kinda off topic but if the asker is asking after those details then maybe they are like me and want more details too...

 

[Packhorse]

............
A reg like the Mk 2 is unbalanced meaning that the 140psi Intermediary Pressure is just that, 140 psi, regardless of how deep you are.

when you get to 120', which is 4atmospheres more pressure than at the surface, that means your local pressure is 60psi (using 15psi/atm for sake of mental math) and thus at this depth with say a Mk2 you would only have the equivalent of 80psi IM... enough to still breathe it fine, but still a noticeable drop, compared to the balanced ones which would deliver 140psi + 60psi so that it still breathes the same as on the surface...

Simply not correct at all.

Yes the Mk2 is unbalanced BUT it is still depth compensating. Its IP wil be 140psi +- above ambient regardless of depth.

The difference between a balanced and unbalanced 1st stage is that a balanced 1st stage will give a constant IP regardless of tank pressure while with a unbalanced 1st stage (piston) the Ip will drop as the tank pressure drops.

As for MK25's vs MK17's.... I own 2 MK25's and 2 MK20's (+a MK2 and MK5). I only service them when they need it. They have not required it yet with 300 or so dives on the Mk25's. Mk20's have less and I serviced them when I 1st got them second hand.
I cant say anything bad about them.
If given the choice Id get the MK17's.... or would I ??? Is the grass really greener on the other side?

 

[keyshunter]

Simply not correct at all.

Yes the Mk2 is unbalanced BUT it is still depth compensating. Its IP wil be 140psi +- above ambient regardless of depth.

The difference between a balanced and unbalanced 1st stage is that a balanced 1st stage will give a constant IP regardless of tank pressure while with a unbalanced 1st stage (piston) the Ip will drop as the tank pressure drops.

Thank you, Packhorse. You saved me some typing. Some people do not seem to understand this concept.