The lowest temp you have taken your MK25 to.

[ajduplessis]

40 was the max for me. No problems thou

 

[Pullmyfinger]

44 for me, in salt water. I experienced no problems.

-Mitch

 

[CPH]

I dive under ice with no problems.
My friend in Norway dives under ice alot and in the cold fjords.
The secret is not to breath BEFORE you get the regs under the water. Most of the time, the water is warmer than the air, so breathing in the air will cause them to get very cold. The temp of the water helps to stop them freezing.

 

[Pedro Burrito]

I'm had my Mk25 down to 42° F in fresh water a few times. My Scubapro tech told me to never take a Mk25 below 52° F. Then he tried to sell me a Mk17.

 

[elan]

I'm had my Mk25 down to 42° F in fresh water a few times. My Scubapro tech told me to never take a Mk25 below 52° F. Then he tried to sell me a Mk17.

Haha I guess 52 comes from roughly 10C which they consider a cold water.

I see folks diving 25th here in 40f range paired with a good cold water second like g250 or an apeks which made me getting them with no hesitation. Some dive tthem even with the older S600 with a plastic barrel but I have seen S600 freeflowing in that water on mk17

 

[elan]

I dive under ice with no problems.
My friend in Norway dives under ice alot and in the cold fjords.
The secret is not to breath BEFORE you get the regs under the water. Most of the time, the water is warmer than the air, so breathing in the air will cause them to get very cold. The temp of the water helps to stop them freezing.

CPH you are right we never breath the regs until we hit the water. Even Apekses or any enviro sealed reg.
If in the shallows we submerge the 1st stages as well as the seconds for sometime to let them heat up and then go down. Or just drop a stage before the dive and start breathing from it as it would be warm by that moment.
We then do a bubble check and might switch to the back gas.
In winter sometimes we dive at -10 c temp while the water is +2


I have seen Apekses and poseidons flowing simply because the divers were testing the reg at -10

 

[Graeme Tolton]

Nothing is foolproof. even the best regs will freeflow if not set up properly. For my cold water apeks, i have the ip turned down to 130 psi. I have only ever had 1 freeflow on them and that was a result of inflating a lift bag at 140' in 37 degree water to recover a mooring line at a wreck site. Scary part was having the secondary freeflow at the same time. I kept cool and got everything under control. That being said, i lost 1000 psi in a matter of about 10 seconds.

I did also have with me a stage of air, but managed to not need it.

Having not only the proper regs, but proper tuning is absolutely necessary.

 

[elan]

I have them set at about 130-135 (hard to say exactly with the gauge I have)

What happen to you sounds like there was a bit of moisture either in the regs or tanks.
I had the same happen to me on the Ceder once. I think the regs were not dry and a bit of moisture got into the regs. 2 out of 3 flowed

 

[Graeme Tolton]

That is entirely possible. Could have even been a slightly wet fill. Too bad compressors cant always be run in cold weather.

 

[halocline]

I'm not sure the lower IP actually does anything, especially with high performance 1sts, and balanced 2nd stages. The idea is that lower IP=less flow to the 2nd stage, and to a certain extent less adiabatic cooling at the 2nd stage, because IP is closer to ambient. But, the lower IP also results in a bigger drop at the 1st stage, which means at least theoretically more adiabatic cooling at the 1st stage, so with a MK25, that point might be your most free-flow prone. This is all speculation on my part....but I suspect the old school practice of lowering IP for increased freeze resistance is more effective with lower performance 1sts and/or unbalanced 2nds, where the 2nd stage does really slow down the flow when presented with lower IP.

Certainly full purges are likely to have a bit more flow at 145PSI than 125PSI.