Mix & match 1st & 2nd stage?

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scv

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Hey guys,

I have an old (2000) Aqualung Titan 1st stage that I just had serviced. I’d like to get a nice second stage reg, but I’m curious if there are limitations on compatibility.

I really want the Poseidon XStream, but will it function properly with the Titan 1st stage?

Other second stages I am considering are the ScubaPro S560, Atomic Z3.

If I hold onto the Titan, would I be better off staying with Aqualung and get a Legend mbs second stage?

lastly…what are everyone’s thoughts on the Hollis 500SE with DC7 1st stage?
 

LiteWeight

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I do not know what the Aqualung Titan intermediate pressure is (and won't look), but if you REALLY want to do that I would verify that the Poseidon 1st stage IP is the same.

Aqualung Legend 2nd stages have a great reputation, I've had several. Although they were LX and I'm not familiar with MBS. If I were you I would get a Legend 2nd stage and octo.

Mixing/matching 1st/2nd stages can be done if you match the IP's, but it really makes it a pain in the a$$ on your reg tech when it comes time to service.

My advice, which is worth exactly what you paid for it, is get Legend 2nd stage and octo.
 

lowwall

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Certain Poseidon second stages require a higher than standard intermediate pressure (IP) to work correctly. The Jetstream is not one of them, but you will have to use their proprietary hose or adapter to allow for overpressure relief. IMO, if you want a Poseidon second, you are best off just getting their whole system.

The next point is that you are going to need two second stages and they'll have to work in the same IP range. For example, you wouldn't want to mix Mares and ScubaPro seconds. Do you already have a second stage you will be using for an octo or are you going to be getting two seconds?
 

rhwestfall

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Modern Poseidon firsts have an OPV in the body.....
 

lowwall

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The IP spec on the AquaLung Titan is 135 (+-5) psi. This will work with nearly all the standard or "barrel" type regs from ScubaPro, AquaLung, Apeks, Atomics, Hollis, HOG, Deep 6, etc.
 

runsongas

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you can retune the titan lower to the recommended IP for the jetstream/xstream, but you will need to add an opv to the first stage or use a downstream 2nd as an opv (instead of 2 upstream ones like the jetstream/xstream). a used poseidon first stage isn't too expensive to swap out the titan altogether, but finding a good poseidon tech is the bigger issue.
 

lowwall

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Modern Poseidon firsts have an OPV in the body.....
But he was asking about using a Poseidon second with a non-Poseidon first that does not have an overpressure valve.

BTW, from the Poseidon Regulators FAQ , the spec incoming IP for Jetstream seconds is 123 psi. It's likely your first stage would need to be tuned for everything to work properly throughout the full range of tank pressures.

Edit: comment moved to next post.
 

lowwall

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you can retune the titan lower to the recommended IP for the jetstream/xstream, but you will need to add an opv to the first stage or use a downstream 2nd as an opv (instead of 2 upstream ones like the jetstream/xstream). a used poseidon first stage isn't too expensive to swap out the titan altogether, but finding a good poseidon tech is the bigger issue.
To expand on this...

If you want to use a Poseidon second with a non-recent Poseidon first, you'll need to figure out an overpressure valve. Most second stages work as OPVs because they freeflow if the IP gets too high. Poseidon upstream seconds won't, so early Poseidons had the OPV built into a fitting on the end of the hose. Now they've moved it to the first stage, but you will need to include your own either by using a Poseidon hose with OPV fitting, adding an OPV to a spare LP port on your first stage, or mixing your second stages by using one Poseidon and one standard second.

If you have a spare LP port, the second option is the easiest. An OPV is $5 from dgx

Over-Pressure Relief Valve (User Adjustable)
 
OP
S

scv

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you can retune the titan lower to the recommended IP for the jetstream/xstream, but you will need to add an opv to the first stage or use a downstream 2nd as an opv (instead of 2 upstream ones like the jetstream/xstream). a used poseidon first stage isn't too expensive to swap out the titan altogether, but finding a good poseidon tech is the bigger issue.

What are some used Poseidon models that would work for the Xstream second? I found a Poseidon Regulator 3750 with New 300 Bar Din for $125 on eBay
 
https://www.shearwater.com/products/swift/

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