Dry chamber (mk17) or not (mk25)?

[Robertp33]

The Scubapro MK17 claims to have a dry ambient pressure chamber. "The diaphragm
design prevents the entry of water into the first stage mechanism and enhances a trouble-free operation, even in the coldest conditions."

I don't dive in ice; just the cold off the New England coast. So what if any is the advantage to the dry chamber - just cold water operation and prevention of freezing?

In general, an MK25 is a bit more expensive. What is the big advantage to a piston design over a diaphram - is it just better air flow?

Thanks.

 

[Thalassamania]

Actually the diaphragm is slightly more complex, but I choose it every time.

It can be more accurately adjusted (usually you use a wrench while pistons often require changing shim thickness) and water does not enter the "control chamber."

 

[halocline]

How cold is the water you dive in? If it's 40F or lower, you'd be better off with the environmentally sealed MK17. The MK25 is often used in cold water, but does not have the stellar cold-water reputation that the MK17 has. If you're talking 50s and 60s, you'll have no freezing worries so either one would be fine.

The MK25 does have a higher flow rate, but you won't notice a difference in performance. Think of it as a car than can go 300 mph instead of 200. The piston design is very robust, fairly simple, and with proper rinsing and storage, will go a good long time between servicing. But it's probably not worth paying extra for.

 

[NorthWoodsDiver]

I own 7 mk17's for personal use, I stand by them. I sold my mk25's.

Take that for what its worth.

 

[beanojones]

I know this, rebuilding the piston Scubapros enough made me fall in love with environmentally sealed first stages. It was warm salt water and mostly rental/and instructor's gear, but eventually all open piston designs seem to crap out from corrosion.

But if you take care of your gear and rinse it properly, or dive fresh water, and don't dive it every day, then nothing I just said really applies to you.

 

[Packhorse]

I own 2 MK25s and a MK20. Never had a problem but them I dive in 11deg C water minimum.
But to be honest if I was to replace them I would look long and hard at the MK17's. Main issue for me would be hose routing.

 

[maged_mmh]

But to be honest if I was to replace them I would look long and hard at the MK17's. Main issue for me would be hose routing.

+1 on this.
if only i could find the MK19; which is basically MK17 with same swivel turret like MK25

 

[4sak3n]

Ditto.

When I bought my reg I dearly wanted to get a Mk19 for the turret. The place where I eventually bought my Mk17 from could get me a Mk19 but it would have cost R2000 ( ~$250) more.

There is just no way I could justify spending that amount of money on hose routing but it nearly broke my heart anyway. :depressed:

Ah well, a broken heart is better than a broken bank.

 

[NudeDiver]

Well, I'm confused. Every time I see a reference to the MK17 and the MK25, people, fairly uniformly, agree that the MK17 is better and seem to all but say, "why in the hell would anyone ever buy a MK25 over an MK17?" However, from what I can tell, the MK25 costs more. So what's the deal? Is it really just a case of selling less regulator for more price? There must be something more to it than that. What gives?

FWIW, I have an MK25 and it seems to do just fine in cold water, judging by the 15 or so dives I've put on mine in 5 degree C (or less) water.

 

[maged_mmh]

i'm not expert, but from design point of view piston regs has more reliability & less potential failures than diaphragm i believe