XTX FST, MK17 or DS4 for twins

[goodeatsfan]

I need some advice. I've been using XTX200/XTXFSR yokes for my singles rig and am thinking of doing my RecTriOX in twins. As such, have been looking around at the various options available.

I'm kinda stuck on these two choices at the moment. The Apeks DS4 OR Scubapro MK17. Pairing the second stage for the DS4 is simple... but pairing the MK17's confuse me. We haven't got G250V's here, only G250HP, S600, & S555's. But I'm guessing they're all gonna pair up fine...

My question is this, given a choice, where cost is not in question, which first stage would you recommend? Or should I just go for the XTX FST because of hose routing?

 

[laughingsquid]

Not sure of the dive conditions you'll be diving in, the MK17 would great for ice and/or/ contaminated water. The MK 17 puts out 250 cu ft. The MK 25 puts out 301 cu ft which would be my choice, since I can route any way I need to. The G250 HP would be the best 2nd stage for either the MK 17/25. I'd look at the S600 and the S555 as a backup.

 

[rjack321]

Yeah for warm water you can't beat the hose routing and simplicity of the Mk25. The S600 is a great primary. Just avoid the R380 as a backup, they breath lousy.

I have seen the Mk17 but not quite sure how the hose routing works yet.

 

[Bismark]

I had FST's on my back gas and didn't care at all for the hose routing. Went through a few hoses. The Mk 25's are excellent for routing and then you can't beat the s 600. I now have Atomic's and they route exactly the same as the Mk 25s. Go figure, they were designed by two former scubapro engineers

 

[goodeatsfan]

Not sure of the dive conditions you'll be diving in, the MK17 would great for ice and/or/ contaminated water. The MK 17 puts out 250 cu ft. The MK 25 puts out 301 cu ft which would be my choice, since I can route any way I need to. The G250 HP would be the best 2nd stage for either the MK 17/25. I'd look at the S600 and the S555 as a backup.

I've actually seen this in a few threads and was wondering, any reason why the G250's have a tendensy to be recommended over the S600's? Is it reliability or because of performance?

Atomics are out of the question as we don't get support for them in this part of the World. Although, I have to agree that MK25's seem to offer the BEST routing options, I'm hoping to stick to diaphragm as opposed to piston, but it's not a must.

 

[rjack321]

I've actually seen this in a few threads and was wondering, any reason why the G250's have a tendensy to be recommended over the S600's? Is it reliability or because of performance?

Atomics are out of the question as we don't get support for them in this part of the World. Although, I have to agree that MK25's seem to offer the BEST routing options, I'm hoping to stick to diaphragm as opposed to piston, but it's not a must.

Personally I like the S600 over the G250. But in our stable we only have a ~4-5 yr old G250 (and equally old S600s) and I think they have actually gone back to some previous better performing style lately. I'm not the expert on the G250 2nds by any means.

Why diaphram? With your warmer waters a piston is fine unless they are very silty or somehow contaminated. Small bits of saltwater generally have less impact on piston regs (they tolerate crud better with a more stable IP when old, worn and/or dirty).

I have too much stuff to service so I bring my mk20/25s in to the shop. I get the parts back and the piston/orings look like they could go another 150-300 dives (a year+ at my rate) before they actually need service. Never had one creep up IP-wise either.

Having used some DS4/ATX40s/50s that friends own I can definately say the SPs breathe much nicer. That said, the mk20/25s suck for ice diving. I haven't used them in less than 46F water myself (where I've never had an issue BTW), and I don't plan too. The SP antifreeze system just isn't up to snuff compared to sealed diaphrams (so I hear, I have no intention of proving it for myself).

 

[Adobo]

I've actually seen this in a few threads and was wondering, any reason why the G250's have a tendensy to be recommended over the S600's? Is it reliability or because of performance?

Atomics are out of the question as we don't get support for them in this part of the World. Although, I have to agree that MK25's seem to offer the BEST routing options, I'm hoping to stick to diaphragm as opposed to piston, but it's not a must.

Do a search on some of DA Aquamaster's posts regarding SP G250s. He's got a lot of useful insight.

With regards to first stages, the mk10s/15s/20s/25s are definitely superior for doubles hose routing. In addition to owning a set of mk10s, I own a set of mk17s. You can decent hose routing but you still wind up with some pretty sharp bends.

 

[DA Aquamaster]

I switched from Mk 25's to Mk 17s mostly because I dove extremely cold water and the Mk 25 is vulnerable to freezing up in seawater below 45 degrees.

I am in the minoirty in preferring the Mk 17 over the Mk 25, but I like the MK 17's excellent fully sealed diaphragm design and anything performance it loses to the Mk 25 is performance that is not needed as the 300 SCFM flow rate of the Mk 25 is just extreme overkill. I have otherwise been a life long balanced piston fan and the MK 17 is in fact still the only diapgragm reg I would consider using for technical diving.

I also like the hose routing on the Mk 17 as it routes straight down and is very clean compared to the somewhat messy and disorganized look of the Mk 25. The bends can be a little sharp compared to the standard Mk 20/25 hose routing depending on the tanks and how they are mounted relative to the plate. But if you leave the hose protectors off the bends are not severe and unless you leave your tanks set up for weeks on end, it is not going to be an issue.

The S600 is often touted as being a great reg by people who look down on the G250HP. This is not a very enlightend opinon. It's not the divers fault really, it is just a product of SP's marketing strategy and the industry wide BS that smaller is better, leads to less jaw fatigue, etc.

Internally the S600 and G250HP are identical. Where they differ is that the valve mechanism is powered by a larger diaphragm in the larger G250HP so the G250HP has a mechanical advantage that translated to potentially better performance. The word potentially comes into play as SP detunes them both to the same inhalation effort levels to met really stupid EU freeflow resistance standards - that have no relevance anyway to a flow vane equipped and inhalation adjustable reg in the first place.

The "larger regs cause jaw fatigue" thing is a myth as the G250HP is larger and heavier, but it also displaces more water because it is larger so the bouyancy is a wash. The critical factors in jaw fatigue are in hose lenght and mouthpiece design.

The G250V is SP's admission that they screwed up discontinuing the original G250 which uses a metal air barrel and offers excellent performance with better heat transfer and moisture retention traits that make it both more reliable in cold water and less likely to cause drymouth on a long dive.

The S600's smaller size makes it worth considerng for a necklace mounted backup, and I'd probably choose it over the G250HP in that role but if the G250V were available it would be my hands down choice for both primary and backup.

 

[goodeatsfan]

wow, that was insightful. Thanks DA Aquamaster...

 

[rjack321]

Thanks for the G250 summary DA.

Our 5yo G250 definately has a higher cracking effort than the similar vintage S600. I'm not sure if that's a consequence of tuning or what. But my wife actually uses it as a backup cause she prefers the S600 in her mouth. I would consdier the G250V nowadays although the S600 seems to be more common around here in shops.