New to DIY Poseidon reg maintenance

[AFdivedoc]

I’ve been doing my own regulator maintenance for years now. I started with older Scubapro and Sherwoods, then moved on to US Divers Conshelf and various other USD/Aqualung regs. Soon after came DiveRite, Apex, and then some USD double hose regs. Being a tinkerer by nature, it has really enhanced my love of the sport of diving. I take real pride in having my regs in tip-top shape, and I like the reaction I get when I take those old brass and chrome Scubapros , Conshelfs, or my Phoenix Aquamaster on a dive trip. Of course, as with any hobbyist, I can’t say I’ve saved any money overall—quite the opposite!

I recently came across some used Poseidon Jetstreams for a good price. They were a little worse for wear and had seen a fair amount of salt water, but I decided to take them on as a project. I had never used Poseidons, but I certainly knew friends who swore by the brand. I downloaded the repair manual from VDH, and read the applicable parts of Vance Harlow’s book, “Scuba Regulator Maintenance and Repair.”

Here are some observations and lessons learned from this project:

The manual: Available in pdf format. It covers several models of Jetstream, Diveair, and Cyklon models. The model designations are confusing. If you print the manual, there are no page numbers, and there is not a functioning index. Thank goodness for the text search function in Adobe! The manual is not the easiest to understand, and there are some typos. The illustrations are not very clear in some areas. The Xstream manual is a separate download, and looks to be a bit easier to use.

Parts availability and cost: DGX has repair kits and pretty much every individual part you will need. I had to replace a DIN connector and insert, and the “piston” of a model 3950 first stage, which I think is more of a movable hard seat. That part is only $15, and a replacement plastic soft seat is only $5. Other parts are quite expensive. For instance, the Jetstream second stage cover is held on with four small screws. On a couple of the second stages, one of the screws broke off flush with the housing insert due to corrosion. As far as I can tell, the only way to resolve the issue is to buy a new second stage housing for $105! I would recommend periodic inspection and lubrication of the screws. Also on the Jetstream second stage, the valve tube is screwed in or out to adjust the breathing resistance and prevent freeflow. Once it is adjusted, it is held in place with a small set screw. The threads of the valve tube are protected from the set screw by a “rubber plate,” which measures about 2.75 mm X 1 mm or so (rough dimensions). The cost of that little piece of rubber is $19 if bought individually (it is included in the maintenance kit, however). I had to replace one servo valve for $45. The O-rings are mostly metric, and available at McMaster if you wish to go that route. Scubaboard member tbone1004 has compiled the correct sizes and many of the McMaster part numbers: Poseidon O-Ring Types and Size info

Non-standard hose connections: At least one of the second stage hoses was not serviceable. Poseidon uses a proprietary connection to the second stage, which used to require only using Poseidon hoses (there was a pressure relief valve in the older model hoses, but now this included in the first stage). Now, you can get a second stage Poseidon adapter for Jetstreams and Xstreams from DGX ($14) which allows the use of standard hoses.

Ease of maintenance: I was pleasantly surprised at how easy the regs were to take apart and get back together. I did have to puzzle a bit over some of the diagrams. There are some tools you can get from Scuba Clinic Tools that make the job easier. The prices are reasonable, although they may take a while to get to you if you are in the US, since they are shipped from Asia. The Jetstream second stage is unlike anything I’ve ever worked on, but really not very complicated. The final adjustment on the valve tube can be made using a hemostat through the mouthpiece opening.

Final result: These are very nice breathing regs—they live up to their reputation! I’ve checked them out in the pool, and I’ll be taking one of the reg sets to Bonaire soon.

 

[Gareth J]

With regard to the hoses, remember that the Jetstream is an Upstream valve, not a down stream.

The hose on a Jetstream is the pressure relief valve. If a first stage fails, or the Interstage Pressure creeps up, on a conventional down stream, the pressure can force the second stage to open (it works against the spring). With an Upstream, the increased interstage pressure forces the second stage closed, i.e it doesn't automatically vent by opening. The hose has a sprung interface which opens when the I/P increases above the specified release pressure.

 

[AFdivedoc]

Yes, the second stage Jetstream is an upstream valve. The current manufacture Poseidons have the pressure relief built into the first stage though (since 2008). The only thing special about the hoses now is the second stage regulator end fitting. Using the Jetstream second with the older first stages does require the special hose or you have to add an OPV to a LP port on the first stage.

 

[Gareth J]

Thanks for that AFdivedoc, I didn't know about the change to an OPV.

I generally use Cyclon's.

One word of warning when using a Jetstream. They deliver gas very positively (aggressively?). The second stage has a large internal volume, so there is a lot of water in one if you remove it in the water. If you clear a Jetstream by hitting purge, it clears quickly, and is known for picking water up and throwing it into the back of your throat. A trick is to tip your head so the diaphragm is lower than the hose end, this helps to ensure you force all the water out when hitting purge, don't breath in at this point, wait until you have released the purge. Using this technique reduces the risk of leaving water inside the second stage, which when you breath in hits the back of your throat.
As you are already aware, it is quite hard to actually press the purge (compared to a 'standard' second stage).

I hope that makes sense.

 

[AFdivedoc]

I did notice the purge is a bit on the aggressive side, and that it takes a bit of force to activate it.

I look forward to diving these soon. Thanks for the tip, Gareth J!

 

[Gareth J]

They are a lovely breath once you get used to them. They are not good on an empty cylinder, you need gas to inflate the 'condom' in the second stage. They are also better deep than shallow.

I look forward to your feedback once you have played with them a little.

 

[tbone1004]

if you tune them properly they breathe just fine at 5ft. Most of the time they are not tuned properly which causes them to flutter when shallower than 15ft.

They do start to freeflow once the tank pressure goes below the IP. I.e. 125psi at the surface, 150 at 30ft, 180 at 100ft, etc. Be mindful of that. Now on a normal reg they just start breathing really hard so it's not like that is usable gas anyway.

you definitely have to commit to hitting the purge button though which is good

 

[Bigbella]

if you tune them properly they breathe just fine at 5ft. Most of the time they are not tuned properly which causes them to flutter when shallower than 15ft.

They do start to freeflow once the tank pressure goes below the IP. I.e. 125psi at the surface, 150 at 30ft, 180 at 100ft, etc. Be mindful of that. Now on a normal reg they just start breathing really hard so it's not like that is usable gas anyway.

you definitely have to commit to hitting the purge button though which is good

One word of warning when using a Jetstream. They deliver gas very positively (aggressively?). The second stage has a large internal volume, so there is a lot of water in one if you remove it in the water. If you clear a Jetstream by hitting purge, it clears quickly, and is known for picking water up and throwing it into the back of your throat.

I definitely have to agree, that the complaints voiced above, have to do far more with poor servicing and / or tuning, than the nature of the regulators themselves. Mine don't free-flow, regardless of the tank pressure, though I am not in the habit of completely draining one; and I've never had a wet breathing experience, regardless of my position in the water column.

Last year, I took a decades-long Scubapro stalwart out for a dive in Carmel; and he experienced a unforeseen free-flow problem with his second stage, upon pressurizing it; so I loaned him some redundant gear I had on hand. He dove with Jetstreams for the first time; was taken aback at how nicely they breathed; and bought a set within ten days of that dive . . .

 

[AFdivedoc]

They are a lovely breath once you get used to them. They are not good on an empty cylinder, you need gas to inflate the 'condom' in the second stage. They are also better deep than shallow.

I look forward to your feedback once you have played with them a little.

Update: I used these regs on my recent Bonaire trip. I'm now a fan. They're right up there in rotation with the other regs I grab for trips like my beloved Mk5/109s and Conshelfs.

 

[Gareth J]

Update: I used these regs on my recent Bonaire trip. I'm now a fan. They're right up there in rotation with the other regs I grab for trips like my beloved Mk5/109s and Conshelfs.

As I previously said, I use Cyclons, rather than Jetstreams

As a user, how you got on with purging the Jetstreams in the water?