Side exhaust reg rcomendation
- Thread starter Candiru
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Hollis 500se, hands down.
I service both Poseidon and Hollis, and both are ready to tune, but Poseidon is more finicky, and parts are more expensive.
And if you care, the Hollis is a DOWNstream servo valve, while the Poseidon is upstream. All that means is that if you have IP creep from your first stage, you'll get an earlier warning with tiny freeflow from the servo valve, rather than sudden release of overpressure from the OPV.
Finally, the 500se is drier than its predecessor.
The first stage is rated to 100% O2.
I service both Poseidon and Hollis, and both are ready to tune, but Poseidon is more finicky, and parts are more expensive.
And if you care, the Hollis is a DOWNstream servo valve, while the Poseidon is upstream. All that means is that if you have IP creep from your first stage, you'll get an earlier warning with tiny freeflow from the servo valve, rather than sudden release of overpressure from the OPV.
Finally, the 500se is drier than its predecessor.
The first stage is rated to 100% O2.
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Only two cautions.
The main valve diaphragm seal only goes in one way, and the edge is delicate. Work it into the body of the valve VERY carefully, so as not to catch on the threads that hold the rest of the valve assembly. A large diameter wooden dowel is helpful here, along with a little Tribolube.
The case is susceptible to damage if you wrench on your hoses too vigorously. I make a habit of unscrewing the valve from the case, sliding it out, and THEN attaching the hose. That way, there's no tendency for the valve to rotate inside the housing when you tighten the hose nut.
The servo valve is sturdy, and rarely needs replacement.
Tuning can be a pain because the diaphragm gets depressed as you try to adjust the very convenient plastic screw in the center. It's very helpful to use an On-Off slider to switch off IP gas pressure from the first stage as you screw in or out an eighth of a turn. Otherwise it's blowing air all over the place.
Hope this helps!
The main valve diaphragm seal only goes in one way, and the edge is delicate. Work it into the body of the valve VERY carefully, so as not to catch on the threads that hold the rest of the valve assembly. A large diameter wooden dowel is helpful here, along with a little Tribolube.
The case is susceptible to damage if you wrench on your hoses too vigorously. I make a habit of unscrewing the valve from the case, sliding it out, and THEN attaching the hose. That way, there's no tendency for the valve to rotate inside the housing when you tighten the hose nut.
The servo valve is sturdy, and rarely needs replacement.
Tuning can be a pain because the diaphragm gets depressed as you try to adjust the very convenient plastic screw in the center. It's very helpful to use an On-Off slider to switch off IP gas pressure from the first stage as you screw in or out an eighth of a turn. Otherwise it's blowing air all over the place.
Hope this helps!
Deciding what your true cracking effort is can be a challenge. The 500SE servo valve opens before the main diaphragm, so which do you pick? The slight flow of air when the servo cracks, or the true inhalation flow when the main valve opens?
If you choose the main valve at 1", then the servo is going to be around 0.7".
If you tune lightly given the advantages of the close set diaphragm and exhaust valve, then 0.7" main will give you 0.4" servo, which can be a little twitchy.
I dive mine that way, but I wouldn't give it to a customer that lightly tuned.
If you choose the main valve at 1", then the servo is going to be around 0.7".
If you tune lightly given the advantages of the close set diaphragm and exhaust valve, then 0.7" main will give you 0.4" servo, which can be a little twitchy.
I dive mine that way, but I wouldn't give it to a customer that lightly tuned.
chrisch
Contributor
Hi @rsingler I have been looking at the Hollis to replace an old Dacor reg. Can you tell me if the flex hose is a standard fitment size and can be replaced with a HOG length one? I am weighing up the cost of a service on the old reg (now a Mares) and a new Hollis. (I can reuse the existing hose of course). There is a square plate in the Dacor that allows a little movement and leak from the 2nd stage poppet. It appears to be a design issue and a good reason to upgrade.
Hose discussion taken off line 
runsongas
Contributor
my vote is for a used poseidon jetstream. rugged, proven design and very high likelihood you can still get parts for it in 25 years. wouldn't say the same about the oceanic/hollis.
A very valid point.
And for deep diving? Unsurpassed air delivery.
Since the OP is going to do own service, that issue is out of the way. Lots of Jetstreams available.
Still, having dived Poseidon for decades, I have to admit that Hollis fixed all the quirks that the old Omega had. It's a nice, compact design, and "sips" more like a traditional valve design than the Jetstream.
A tough call.
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