Apeks VS ScubaPro

[Tamas]

Theoretically, the larger port would allow more air to flow through the port with less impedance. The effectiveness of this port supposedly increases at depth as the air increases in density. The couter argument to this is that at extreme depth most people use helium in the mix. Helium is much lighter than oxygen and nitrogen and breathes much easier.

It seems that the atx50 is sold paired with the DST, but you can usually just ask for the DS4 instead. If you are seriously looking, I repeat "call divetank..." they have DS4's and atx50's for great prices. They will quote each part seperately even the hose and might give you a bigger discount for a package.

So I guess you would also need special hoses for that as well if you were to use that methodology. Thanks.

I might, but first I will give my LDS a chance to bid on it first. Still not sure which one to get though.

I also like the smaller and lighter second stages of the ATX100 and 200's compared to the 50's, but I guess that is interchangeable as well.

 

[RTodd]

So I guess you would also need special hoses for that as well if you were to use that methodology. Thanks.

I might, but first I will give my LDS a chance to bid on it first. Still not sure which one to get though.

I also like the smaller and lighter second stages of the ATX100 and 200's compared to the 50's, but I guess that is interchangeable as well.

I have been thinking about the 200s but they haven't passed the bullet proof reliability test. Plus, the useless 1/2" port is nock against it. Finally, there is a push for smaller second stages on regs these days. While this depends on the diver, smaller seconds tend to have a "more annoying" exhaust (for me at least) that tends to put more bubbles under a hood.

 

[Tavi]

I really like my Atx200's, If the 1/2 inch port is an issue with your routing just carry a spare hose, My hoses route very nicely, and I like the smaller second stages compared to my Tx50regs.
I've had these regs in 39f water, and to 204'. Always breath great.
I was on a dive last year, 8 of us on the boat. water temp was 49f. The only freeflow was the 1 diver with ScubaPro regs (I don't know which model).

 

[Hoosier]

I had one free flow in 40 degree water. My reg tech added an o-ring to the first stage (serving as a spacer so the piston could not bottom out in the chamber) and I have never had a free flow since. This suggestion came from a tech at SP. I have been using my SP reg the last two months in water as cold as 35 degrees F. I have the reg set just shy of cracking pressure as well. ~~~~~~~ Since the adjustment I mentioned above, I have not experienced a free flow problem even in 35 degree water. I have friends that regularly ice dive with their SP MK25/S600 (exact same reg as the G250 HP just smaller/with smaller face plate and 2nd stage diaphram).
--Matt

Wait~~. It is a new interesting findings. I think it is the time to ask some comments about this method to our SP expert, DA Aquamaster here. How do you think, DA Aquamaster? Thanks in advance,

 

[akscubainst]

Of the two brands in question, I have only used Scuba Pro. I use the MK25/G250 HP as my first primary on my tech rig. I am at the 'intro to tech' phase so I have been no deeper than 160'. I was completely impressed with the ease of breathing at this depth. I bought my reg brand new last year so it had the AF components. I had one free flow in 40 degree water. My reg tech added an o-ring to the first stage (serving as a spacer so the piston could not bottom out in the chamber) and I have never had a free flow since. This suggestion came from a tech at SP. I have been using my SP reg the last two months in water as cold as 35 degrees F. I have the reg set just shy of cracking pressure as well.

--Matt

We called Scubapro Tech Services today and inquired about this fix. They were adamant that this is NOT a Scubapro recommended modification.

The O-ring that is supposed to be added to older MK25's is under the cap that covers the HP seat not under the piston. Even then this is reall only necessary for the Aluminum bodies to prevent corrosion but for simplicity they added it to all MK25's. If your reg is only a year old then it should have already had the o-ring I mention.

For safety sake you might want to confirm with your tech what he really did. I'd hate for that oring to get blown down your reg hose while you're diving.

Dave

 

[matt_unique]

We called Scubapro Tech Services today and inquired about this fix. They were adamant that this is NOT a Scubapro recommended modification.

The O-ring that is supposed to be added to older MK25's is under the cap that covers the HP seat not under the piston. Even then this is reall only necessary for the Aluminum bodies to prevent corrosion but for simplicity they added it to all MK25's. If your reg is only a year old then it should have already had the o-ring I mention.

For safety sake you might want to confirm with your tech what he really did. I'd hate for that oring to get blown down your reg hose while you're diving.

Dave

I double checked with my reg tech (aka my tech instructor). The O-ring is behind the piston (under it) and keeps it slightly off the metal. This keeps freezing metal from coming into contact with the piston base.

Based on your call it appears not everyone at Scuba Pro is suggesting the same thing. For cold water purposes (40 degrees F and colder) the SP tech suggested a check of the IP (it was fine), detune the 2nd stage a bit, and to add this o-ring under the piston as described above. I immediately changed the 2nd stage back to *just about* cracking pressure because I did not like the initial adjustment. I have made 40 dives on this reg since the o-ring addition as deep as 160' and as cold as 35 degrees F without any problems. I mention the latter only to convey the fact that it has been put through some paces (since the addition) and breathed like a champ. I am curious as to why one SP tech made this suggestion while another apparently did not?

--Matt

 

[Wijbrandus]

I bought my G250/Mk25 last month. I've only had the chance to use it in the Carribbean, but I could tell absolutely no difference between that and the S600 (that I'd rented every dive beforehand). I like the G250 for the larger size. The S600 was just a little too small to feel comfortable to me. I won't have a chance to test it in cold water until the spring though. I am curious to see how it will perform, and if I'll have any free-flows.

I had checked into getting an Apeks DS4/TX50 set. There was only one place that I found that was willing to service it - the place I would have had to buy it if I wanted to buy locally. I won't go to that LDS anymore (for other reasons), and so Scubapro was the natural choice. Everyone services scubapro regs just about.

 

[DA Aquamaster]

WhenI first saw the description of the extra o-ring, I was a little confused so the varying responses SP reponses that this is is and is not an approved approach are understandable.

I have heard of placing an extra piston o-ring in the compression chamber above the piston to prevent it from contacting the top of the compression chamber. This would potentially prevent a stainless steel piston from wearing metal off the top of the compression chamber in an aluminum swivel cap in an UL reg but it would also limit the working range of the piston and potentially the flow rate, so it is not a great idea in general.

But I don't think an extra o-ring above the piston is what was meant.

The newest Mk 25 piston is a composite design with a stainless stem and a plastic head. This piston also comes with a plastic bushing that covers the piston. This bushing provides additional insulation and also provides a groove for a second piston head o-ring. This would be the o-ring in question. Although it does not prevent the piston from contacting any cold metal, it does help keep water away from the piston head itself by acting as sort of a squeegee. Given that the working range of the piston is also relatively short, the second o-ring keeps the area where the piston head and its primary o-ring travels dry.

There is also a rubber "soft sleeve" on the piston stem that keeps water off the piston stem and also flexes as the piston cycles to crack off any ice that may form on the sleeve itself. This sleeve does keep ice form forming on the base of the piston stem which can get quite cold with the air flowing through it.

In my experience the G250 has less potential to freeze than the S600. The S600 seems to have problems with a slight freeflow in cold water and this slow but constant flow aggravates the cooling situation for the Mk 25 first stage. Essentially, the S600 is giving the Mk 25 a bad name in cold water.

SP's approach to try to address this is basically to reduce adibatic cooling by reducing flow rate by lowering the IP to 120-125 psi. Detuning the second stage is an effort to reduce the unintentional flow of air to again reduce the potential to initiate a freeflw that may freeze the first stage.

It is a good idea on the S600 but is not in my opinion all that critical on a G250. I have had similar luck with D400's on Mk 20's and 25's and have never managed to have one freeze up even with water temps as low as 35 degrees.

 

[Hoosier]

OK, I take your opinion, seriously. If then, do you think how often the regulator should be serviced to save our AXX? I know that Atomic requires every other year unlike any other major brand. Let us have your opinion in detail?

Thanks in advance,

Disclaimer: Not annually servicing your gear will get you killed.

Scubapro's generally must have annual service. I service my apex at most once every 5 years and they get the most use.

 

[StSomewhere]

I think a lot of tech divers don't use diaphram regs on deco cylinders because if they flood they don't purge the water very well. A piston reg should be able to be removed, replaced and purged underwater and still function (although in need of a service).

OK I'm a little lost here. You're saying that diaphram first stages are bad for stage bottles "because if they flood they don't purge the water very well". Then why wouldn't the same apply to the backup second stage?