Scubapro

[DA Aquamaster]

I went ice diving this past weekend. I opted to switch to my Apeks ATX50. I friend of mine used his MK25AF/S600 with environmental kit and it freeflowed on him after about 10 seconds at depth.

The Mk 25 flows a BUNCH of air (300scfm) and this is it's achilles heal in cold water. The adibatic cooling that can result will overload the TIS system even on the AF model.

You will get much better results with low pressure tanks as the adibatic cooling load is reduced in proportion to tank pressure. 3000 psi tanks really should be avoided in extemely cold water with a MK 25. But the Mk 25 still needs to be carefully handled wth excellent cold water technique to avoid a freeflow in water colder than about 40 degrees.

I am also not a fan of the S600 in cold water and I think it is about half the problem with cold water freeze ups with the Mk 25. With a D400 and low pressure tanks I have never had a freeze up with a Mk 25 in water as cold as 34 degrees. I did 120 dives last year and the average bottom temp ranged from mid 30's to mid 40's and I never experienced a freeze up.

 

[ElectricZombie]

Why won't any SP dealer come off the price even alittle? Trying to buy four MK25/S600 Din setups and our local LDS WILL NOT BUDGE. Crazy
Eddie

The LDS has a pricing agreement with SP. SP dictates the price their products will be sold for and if the LDS does not comply, SP takes the dealership away. There are ways to get around this, but most LDS's don't bother trying. The LDS is most likely not going to come down on the price. Why don't you just buy the reg online and save a ton of money?

 

[hex92]

If you are in good enough with your LDS you can get them for cheaper. Last time I bought a SP regulator I bought it for less than the 30% discount they allow. But the LDS owner filled in a higher price on my warranty registration card that was sent back to scubapro. Of course it was also a ca$h transaction.

Its a case of "what they don't know can't come back to bite you in the ***"

 

[DA Aquamaster]

Most dealers are not going to falsify the documentation they send to SP as they can still get caught because, as you so aptly demonstrate, customers who get a great deal talk when they should not.

Short of doing something blatantly dishonest or illegal, an SP dealer can still give you what amounts to a deep discount by providing you a generous trade in allowance on a used reg or BC.

Alternatively if you are buying more than just a reg, the dealer can give you a drastic discount on an non scubapro item and sell it at or below cost using the mandatory mark up on the SP reg to offset the loss on the other item. It gives you a great deal when both items are conisdered together and it still allows the dealer a fair profit.

 

[Scotty]

I have the MK16/S550 combo. I have not used it yet but everyone I talked to said it should be great. I bought it used (1year old for 150). I hope it works as good as was reported.

 

[pufferfish]

The Mk 25 flows a BUNCH of air (300scfm) and this is it's achilles heal in cold water. The adibatic cooling that can result will overload the TIS system even on the AF model.

You will get much better results with low pressure tanks as the adibatic cooling load is reduced in proportion to tank pressure. 3000 psi tanks really should be avoided in extemely cold water with a MK 25. But the Mk 25 still needs to be carefully handled wth excellent cold water technique to avoid a freeflow in water colder than about 40 degrees.

I am also not a fan of the S600 in cold water and I think it is about half the problem with cold water freeze ups with the Mk 25. With a D400 and low pressure tanks I have never had a freeze up with a Mk 25 in water as cold as 34 degrees. I did 120 dives last year and the average bottom temp ranged from mid 30's to mid 40's and I never experienced a freeze up.

What is the difference between the D400 and S600 assuming the same tank pressure and MK25AF first with regard to freeze up risk?

 

[DA Aquamaster]

In my opinion the S600 is much more prone to slight freeflows than the D400 when tuned for maximum ease of breathing.

Due to the case geometry and the relative locations of the diaphragm and exhaust valve, the D400 is not prone to freeflows in different orientations. With an S600 if the reg is tuned for minimum cracking effort by the diver in a vertical position, it will freeflow slightly when the diver moves to a face down position as the top of the exhaust valve will then be substantially higher than the center of the diaphragm. Consequetly the adjustment knob will need to be cranked in a turn or two to prevent the pressure differential (which can be as high as 1.2 inches of water) from opening the poppet. But the air lost in the process adds to the cooling load on the regulator.

With the D400 you can maintain a cracking effort as low as .6 inches of water and move into virtually any position and not encounter a freeflow as the exhaust valve is located in the center of the diaphragm and the pressure differnetial is never more than about .5 inches of water.

The SP recommendation for the S600 and it's other currently produced second stages in cold water is to detune the second stage with a cracking effort in the upper end of the range. In the case of the S600, 1.5 to 1.8 inches of water is recommended to prevent any inadvertant airflow. But with a cracking effort like that why spend money on an S600? Just save some big bucks and buy an R190 because it will breathe every bit as well as your cold water detuned S600.

 

[pufferfish]

Thanks DA. Yes those 'slight' freeflows are what make me a tad jumpy in cold water. Never had a fullblown freeflow with the MK25AF/S600 but it always seems like it is just on the edge and that is with optimizing all the other factors to reduce the the risk of free flow (lower IP, dry air, minimize flow rates, etc.). Maybe it is time to just accept this is not the best reg combo for cold water diving and to have a look at Atomic, Aqualung, or Apeks.

 

[hogluvr]

I'm seeing the references to MK25AF, on this board, but not on SP's web site. I read that it's a delaer installed kit. What's it entail? What's it supposed to do? Does it work?

I'm contemplating the MK25/S600 arrangement, doing most diving here in NJ. I'll be diving mostly May through Sept. Will this reg cause me problems?

Larry

 

[DA Aquamaster]

I'm seeing the references to MK25AF, on this board, but not on SP's web site. I read that it's a delaer installed kit. What's it entail? What's it supposed to do? Does it work?

I'm contemplating the MK25/S600 arrangement, doing most diving here in NJ. I'll be diving mostly May through Sept. Will this reg cause me problems?

Larry

All Mk25's currently sold will be equipped with the anti-freeze kit, so there really is not a MK 25AF in the same sense of the word as there is a Mk 25T or Mk 25 SA as every Mk 25, whether it be a Mk 25, a Mk 25T or a Mk 25 SA will have the AF kit.

The AF treatment includes the composite piston that provides better insulation than the older all metal pistons. It also includes a piston bushing that is slightly redesigned to reduce ice formation and a rubber sleave on the piston stem that both insulates the stem and flexs to break loose any ice attempting to form on the stem. And it includes the finned cap on the reg that gives the Mk 25 "AF" a Borg kind of look.

You will have no problems with a MK 25 S600 in water down to 50 degrees, and you should be fine in water in as cold as the mid-40's if low pressure tanks are used. I have been fine in water in the upper thirties but I use low pressure tanks and was very careful to use good cold water technique with the reg.