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The Natural
October 31st, 2005, 01:05 PM
So I've narrowed it down to either the Scubapro MK25/s600, the Zeagle Flathead or an Apeks ATX50. So what do you all think, what are your preferences?

October 31st, 2005, 01:20 PM
This is religious ground you're treading on... From what I can see, all are excellent. Clearly for cold water, the piston will be the most problematic. The Zeagle flathead is an adapted Apeks design. And I don't know much about the ATX50.

This one should get brisk responses! :)

October 31st, 2005, 01:22 PM
So I've narrowed it down to either the Scubapro MK25/s600, the Zeagle Flathead or an Apeks ATX50. So what do you all think, what are your preferences?

For singles or doubles?

For singles, it’s hard to beat the MK25 for neat hose routing. For very cold water use I would go with Apeks.

OTOH, both the MK25 and the Apeks DST first stages (that is usually sold with the ATX50 second stage) have swivel turret—some people would say that they are potential failure points that one does not need.

For doubles, especially for cold water, I would go with the ATX50 (with DS4 first stage)—an even better Apeks choice would be the old TX100/FST (Flathead) combo. The MK25/S600 (bad reputation in very cold water—deserved or not, I don’t know...) does route beautifully though; I would be tempted to get the cheaper (but just as good) MK25/G250HP.

Have never tried the Zeagle.

The Natural
October 31st, 2005, 01:39 PM
This would be for doubles, maybe eventually doing some ice diving, definately not this year though, if anything just some colder ocean diving up here in the north east.

October 31st, 2005, 01:41 PM
If the ATX50 has the DS4 first stage, that would be my top choice.

October 31st, 2005, 01:54 PM
I use a TX50 (basically the old ATX50 - has a larger exhaust) and find it a great reg. Some people like the swivel turret first stage, others hate it. I dont know of any proven failiures due to the extra ring. Ive found hose routing very nice.

As a second stage the TX50 breathes well at all depths and has cracking pressure along with venturi adjustment to control breath. If i had to buy a new set of regs now, id buy the same one again.

October 31st, 2005, 02:17 PM
One thing to consider is Apeks is supported by the Aqualung network so parts will be readily available...while the arguement will rage on, the chances of a swivel going bad are remote at best .....Life is a failure point.......but most teks use the DS4 which is non......I have the TX100 and it has been a great reg.....I have a bias toward diaphram over piston.....good luck on whichever one you choose.

October 31st, 2005, 10:54 PM
Mk 25-

I have been diving the MK 25 in Washington state and Northern Canada for a few years now and have not had a problem, I am a regulator technician and have not heard of one complaint pertaining to freeze up of a MK 25. Scubapro has gone to great lengths to ensure that the Mk25 will work in cold water.

When using doubles the Mk 25 is also an excellent choice. On the swivel section the low pressure port coming out of the bottom of the housing provides 20% more air flow than the rest of the low pressure ports. By adjusting the orientation of the first stage to approximately 45 degrees pointing towards each other you can use the low pressure ports to provide your second stages with air.

As far as the swivel low pressure housing being a point of failure; I haven’t heard of a valid complaint or concern about that being a likely point of failure.


October 31st, 2005, 11:01 PM
This is a good resource for unbiased information:

Now for some biased information: Zeagle makes an awesome regulator-MADE IN THE U.S.A.- GUARANTEED FOR LIFE


DA Aquamaster
October 31st, 2005, 11:08 PM
I used to use Mk 20's and Mk 25's but prefer the Mk 17. It is bullet proof in cold water and I honestly prefer the ability to route all the hoses straight down on doubles with the Mk 17 compared with the turret on the Mk 25.

The Natural
November 1st, 2005, 01:46 AM
I think I am going to go with the MK25, the shop near me will give me a good deal and they are the same regs my dad is diving with, so for swapping around it'll be easier. Now I just need to finish paying off my bass guitar so I can buy these bad boys. :D

November 1st, 2005, 03:57 AM
If the ATX50 has the DS4 first stage, that would be my top choice.


No offense, but this leaves me a bit confused. In your previous post you said you did not know much about the ATX50 but now it would be your top choice?

November 1st, 2005, 08:04 AM
I did not realize at the beginning that the Apeks ATX50 had the Apeks DS4 as the first stage. Once that became clear, that would be my top choice. The DS4 is the first stage I would like to have. It's also inexpensive.

November 1st, 2005, 08:11 AM
The ATX50 is usually sold with the DST first stage. The DS4 is sold by itself and you can pair it with a TX or ATX second stage when you order.

November 1st, 2005, 09:17 AM
I've got a couple of flatheads (Zeagle variety) that I use on my backgas. They're fairly similar to the Apeks design and I think are a bit cheaper as well.

November 1st, 2005, 10:01 AM
The ATX50 is usually sold with the DST first stage. The DS4 is sold by itself and you can pair it with a TX or ATX second stage when you order.

Oh ok, thanks for clearing that up. I was confused.

DA Aquamaster
November 1st, 2005, 10:26 AM
At the risk of being over bearing, let me repeat that having used both, in my opinion buying a Mk 25 is a mistake now that the Mk 17 is available. The Mk 17 absolutely will not freeze flow on you in cold water while the Mk 25 has a bad habit of doing just that in water colder than about 45 degrees.

The 300 SCFM air flow of the Mk 25 is much greater thant the 177 SCFM delivered by the Mk 17, but it is also overkill and a 177 SCFM is more than enough for any technical trimix or deep air situation. The response rate of the Mk 17 is also excellent and it breathes as well as or better than my previous Mk 20's and Mk 25's with the same second stages. The Mk 17 is also fully sealed and this makes after dive maintenence a little easier as there is no ambient chamber to flush.

Based on my recent shopping experience and the various prices quoted to me, a MK 17cost me $50 to $70 less than a Mk 25 with the same second stages.

A not often advertised fact is that your LDS can also order any Scubapro second stage you want with the Mk 17. You lose the slight advantage of package pricing but a Mk 17 G250 HP can still be had for a retail full warranty price of $543 and from a "most bang for the buck" standpoint is the way to go.

In comparison a MK 17 S600 retailed for $598, although the cool thing was that for the same $598 as the MK 17 S600 I could get the pre-packaged Mk 17 X650. I own one and have tested it at depth and in 33 degree water with no issues with freeze ups. If I did not still own several very nice D400's it would be my second stage of choice. And all of the above prices were cheaper as the LDS offerred a 10% discount.

So basically I figured I could save money by going with the Mk 17 and get a better deal on what I regarded as a much better regulator for technical diving, cold water or contaminated water diving in the process.

There's nothing wrong with buying a Mk 25 as it is a well provena nd bullet proof design that offers excellent performance in most diving situations (the only exception being cold water diving). But be sure of your reasons for buying it and understand that you will be paying more money for a regulator that will not deliver any more useable performance than a Mk 17 and that it will be less reliable in cold water.

The Natural
November 1st, 2005, 11:19 AM
Hmmm interesting points to consider. I don't really want to buy a reg that I will have issues with later on down the road when I want to do more advanced diving such as ice diving. I'll take a look into the MK17 with the X650 2nd stage. I'm not too concerned about the price since the guys at the LDS will match any internet prices. I'm definately leaning towards Scubapro now for certain.

November 5th, 2005, 10:09 PM
Personaly I use a Mk25 w/out AF and a G250HP. I've had it down to about 42 with no problems but my partner who had the same Mk25 as I did had a free flow. In my opinion most free flows are caused by setup problems. If the water is that cold you shouldn't be prebreathing the regulator. Also I know many people who dive the MK25's with the internal pressure set a little lower and they never free flow. If I could buy some new regulators I would go with the Mk17. It is spose to be amazing. For second stages my dive shop only carrys two in stock, the X650 and the R190. If you want something else it has to be ordered. You won't go wrong with an X650. So go for the Mk17 X650 or G250HP and it will be a great combination. Also I have nothing against Apeks and if your that worried about cold water Apeks regulators never freeze.


The Natural
November 7th, 2005, 12:06 PM
I think I've decided on the MK17 and the X650.

January 11th, 2006, 12:01 PM
well Ive had my MK25 (DIN) down to under 35 degrees without any freezing problems. I keep hearing people badmouth the MK25 for freezing.

The problem most people have is that they take that first pre-breath/purge in their reg on the beach/boat 5 minutes before they are in the water. The 1st stage's large thermal veins extract heat from the water and allow it reamain warmer longer , but cannot do the same on the beach because most of the time in cold water diving the air is colder then the water and ofcourse much less dense (as we know from basic thermodynamics that there is no such phenomenon as cold--only heat and its loss of energy). Because there is no way to extract heat effectively from air the 1st stage's heat loses its energy and drops in temperature--leading to free flow.

also, wait until you are in the water to change the 2nd stage setting from predive to dive; and to play with flow control.

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