mixing and matching brands

[waterdaughter]

Apologies in advance if this a frequently asked question...or if the answer is more simple than I can discern from the reading I have done, but what are the factors one must consider when mating up primaries and secondaries from different brands/models?

I have an MK25/S600 with a G250 SS; these are DIN. I also have a Viper Metal set which is Yoke and an MK10/G250 yoke. I know it's probably shocking, but I like the Viper's versatility as a SS (since it breathes the same, regardless of the orientation, nobody ever sucks in a mouthful of water if they put the reg in upsidedown).

I would like to use the Viper octo on whatever regs I am diving with, but it has been suggested that putting this design of reg on the either of the SPs primaries,(which are apparently different, mechanically than the Viper primary) won't work.

Without discussing the merits of the G250 vs the Viper as a SS, can anyone explain why it is or is not possible to use the Viper octopus on the MK25 (or the MK10)?

OR... Can I get out my shiny new Scuba tool and go ahead with the switch ?

thanks in advance...W/D

 

[Damselfish]

I slapped a Viper octo on my SP MK 10 about 50 dives ago. I actually asked Larry at Scubatoys and he said it would be fine. And it is.

(The repair guy at my shop has a pretty low opinion of the Viper octo, but that's another matter and I still like it.)

 

[rescuediver009]

The only time that I would see this as a porblem is if you wanted to use the viper as a primary. Because the MK25 is overbalanced it increases the IP at a faster ratethan the viper is designed for. As a result you wold have to detune it very slightly to prevent it from trickling at depth. This is not the best option for a primary.

As a backup (which most people detune anyways to prevent freeflow) I don't see it being a problem.

 

[halocline]

I didn't know that the MK25 increased IP with depth any more than any other reg (IP typically is X above ambient) but I've used a viper as an alternate on my MK15 and it works fine, although it's a lousy breather compared to the G250 or my B/A metal case, which is my usual alternate. I do like the fact that's pretty compact and kind of lays flat when not in use. I usually use it as the alternate on my MK2/R190.

 

[rescuediver009]

Yes, IP is typically X (ATA) over ambient. In an overbalanced (like the MK25, apeks regs, MK16, zeagle regs, etc.) the IP is X (ATA) + Y (overbalancing) + ambient. This makes the reg breathe easier the deeper you go.

How do these regs not trickle. Simple the LP seat is not a flat disc. Simply put it has a hole in the centre allowing air to pass by and to help the apring accomodate for the higher than normal IP creep. Your vipers, R190's and even R390's cannot accommodate this as they have the flat disc seat style. The more common term for the two types is balanced vs. unbalanced.

If you remove the hose from the second stage and look into the second stage, you can see the seat with the hole in the centre.

Sooooooooooo.... at the end of the day your overbalanced first stage should "ideally" be mated to a balanced second stage. The way to get around this is to detune the second stage a little so that the increased IP doesn't cause a trickle. Not desirable with yourprimary but tolerable with your octo (as mentioned).
PS-Not too sure on the over-balancing or lack there of in the MK15

 

[waterdaughter]

many thanks for the helpful explanations!
W/D

 

[DennisW]

You don't have to worry about it, but in the UK, mixing brands is illegal, or so I've been told by several people. Yes, there is government regulation of SCUBA in some countries. I would be in trouble.

 

[Creed]

You don't have to worry about it, but in the UK, mixing brands is illegal, or so I've been told by several people. Yes, there is government regulation of SCUBA in some countries. I would be in trouble.

Really? Why? And does it stop at regs? I regularly use different brands of gauges from the regs they are attached to. This seems to be an insanely stupid law.

 

[halocline]

Yes, IP is typically X (ATA) over ambient. In an overbalanced (like the MK25, apeks regs, MK16, zeagle regs, etc.) the IP is X (ATA) + Y (overbalancing) + ambient. This makes the reg breathe easier the deeper you go.

Not to nit-pick, but are you sure the MK25 increases IP at depth more than the increase in ambient pressure? I just read a post that said that "overbalanced" in some cases refers to the design of the piston and seat which prevents the slight drop in IP that even balanced regs experience at really low tank pressures. Just curious here, because I haven't heard of true overbalancing in SP piston regs before.

 

[bobco]

You don't have to worry about it, but in the UK, mixing brands is illegal, or so I've been told by several people. Yes, there is government regulation of SCUBA in some countries. I would be in trouble.

Hi all,
I’ve been diving in the UK for a few years now and have yet to come across any law that forbids the mixing of regs/gauges etc from different manufactures. I use Apex regs with US Divers gauges, as yet the dive police have not caught me, they will never take me alive eyebrow

Regards and safe diving

Bobco