Cold water reg dilemma

[NudeDiver]

So, I have a 10 year old Sherwood Magnum Blizzard that I recently bought used with 4 or 5 dives on it. Supposed to be great in cold water.

I also have a ScubaPro MK-25/S600 (with the af fins, I believe, but not sure) that I bought new in 2005, and I've got 80+ dives on it. Never had any problem with it in cold water - but I hear on here that it leaves a lot to be desired.

So - here is my question. Once I have the Sherwood overhauled, which one of these would you use for the primary reg, and which one would you use for the pony bottle reg. Feel free to detail the rationale for your answer

 

[DA Aquamaster]

The Mk 25 does fine in cold water until the water temp drops to around 40 - 45 degree F. Below that is is increasingly prone to freeze flows unless you use perfect cold water technique.

The fins on the swivel cap really don't make much difference - compared to common sense things like not having rubber hose protectors covering the hose fittings where they connect to the first stage or covering the second stage inlet fitting. All of those add more area for heat transfer than the fins.

Most freeze flows with the Mk 25 are "small" as freeze flows go and I have even seen one stop freeflowing when the diver ascended into warmer water. So it is a marginal cold water reg that works well in water 50 degrees or warmer, but is not well designed for serious cold water in the sub 40 degree range.

My thoughts are to use the Mk 25 as the primary and the Sherwood on the pony.

1. The Mk 25 S600 will breath better and will not be problematic on any dive in water temps over 45-50 degrees. Why limit yourself to the lower performing reg on 95% of your dives?

2. On dives where it may freeze, you want the bullet proof reliable reg as back up, not vice versa. If the water is cold enough to freeze your Sherwood, your much less cold water capable Mk 25 will follow in freeze flow mode before you even get to the surface so using it as a cold water backup is frankly a realy bad idea. It would provide no real margin of safety as it is less tolerant of cold water than the reg it is backing up.

3. Conversely in the event your Mk 25 primary freezes, you switch to the Sherwood pony reg, turn off the valve feeding the MK 25 and then after a few minutes it will thaw and you can turn it back on to access the rest of your back gas. If it refreezes, you can always switch back to the pony and turn the valve feeding the Mk 25 off again (you can of course reach the valve on your primary reg - right?). That approach makes a lot more sense in a cold water setting.

 

[Hallmac]

I have a 10 year old Sherwood Magnum Blizzard

Quick question as my Sherwood experiences are limited. Does this unit use the dry bleed system or is it a sealed dry chamber?

 

[NudeDiver]

Quick question as my Sherwood experiences are limited. Does this unit use the dry bleed system or is it a sealed dry chamber?

I have no idea. I have the mechanical ability of a house plant. It's all I can do to remember "lefty loosy" when turning a screw.

 

[NudeDiver]

The Mk 25 does fine in cold water until the water temp drops to around 40 - 45 degree F. Below that is is increasingly prone to freeze flows unless you use perfect cold water technique.

That's what I keep hearing...and I highly doubt my cold water technique is anything even remotely close to perfect, it has not given me any problems. Maybe I got a "good one"

compared to common sense things like not having rubber hose protectors covering the hose fittings where they connect to the first stage or covering the second stage inlet fitting.

Doesn't seem like common sense to me Please explain this one to me.

So it is a marginal cold water reg that works well in water 50 degrees or warmer, but is not well designed for serious cold water in the sub 40 degree range.

...and yet, my LDS sold it to me as a perfect cold water reg. Damn!!

My thoughts are to use the Mk 25 as the primary and the Sherwood on the pony....

Your rational seems very reasonable to me. Thanks for that level of detail. Based on your response, I have to assume that this Sherwood is in fact a good cold water reg?

you can of course reach the valve on your primary reg - right?

I really doubt it. Once I get in my drysuit, I can't reach much of anything. However, I'll be in the pool tonight - I'll give it a try and see what happens.

Thanks for your comments

 

[Xaryo]

Quick question as my Sherwood experiences are limited. Does this unit use the dry bleed system or is it a sealed dry chamber?

The cold water reg of Sherwood (Brut, Blizzard and Maximus) use the dry bleed system. So there is always tiny bubbles coming out of the first stage. It is ment to be that way. No bubbles=troubles.

The newest reg of sherwood (SR1) doesn't use the dry bleed system. Instead, the first stage is sealed with a rubber diaphragme.

As for the other Sherwood reg, I don't think they should be used in cold water.

 

[Dockmaster]

The Sherwood Blizzard is a very popular here in Maine. My first dive instructor, a former captain of the Maine State Police Dive Team, swears by them. Now that he's retired from the SP, he does recovery jobs when cars, trucks, and snowmobiles go trough the ice, as well as ice diving classes. His regulator of choice; Sherwood Blizzard.

I have a 10 year old Blizzard as well, and though I have not been ice diving, I have used it for cold water/air temp dives without any issues whatsoever. I have also had very few freeflow issues on the surface. The thing is rock solid.

 

[DA Aquamaster]

The Blizzard has a dry bleed system which keeps the ambient chamber free of water (unless you descend really fast) and consequently keeps ice from forming inside the ambient chamber.

Keeping hose protecters off the metal fittings allows more water flow over them and enables them to help transfer heat from the warmer surrounding water to the first stage - which is being cooled by the expanding air passing through it.

SP has marketed the Mk 25 as a great cold water reg. it really isn't. The fully sealed and decent surface area'd Mk 17 is fantastic in cold water and before it the Mk 16 and Mk 2 were very good - better than the Mk 25. Which means, contrary to dealer claims, the Mk 25 is the only SP second stage sold in at least a decade that is not a good choice for cold water diving.