Just got my new JJ in this morning!!!

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Here are my tips that no one has mentioned yet.

Take care of your HUD!!!! The new divecan Shearwater HUD might be the weakest link on the JJ and all other units that are using this HUD. When your carrying your head around make sure you tuck the HUD into the fabric hose protector so its not flopping around. I have seen two of them crack from people letting them flop around and hitting stuff while being carried, also have seen two of them flood. Only plus side is if this happens just give Shearwater a call and they will replace it for free, just a hassle if your located in a remote area.

Next tip is if you do a battery change take special care not to pinch inhalation hose corrugation on the battery cover. If you do this the battery cover will not seal correctly and you will flood it resulting is the head needing to be sent back to Denmark for all new electronics replacement. I have not done this but someone I know did.

Always check your MAV buttons during your predive check. If you are diving saltwater and since the MAV's just use regular BC inflation connections they ted to let in a little more water in than QC6/QC4 connections so if your doing lots of off board plug ins/dill switches I find the JJ MAV always need a little extra TLC so they don't get sticky about every 25 hours I re-grease the o-rings on mine or just when you can see the button is not popping out like it normally does (plus always change them out annual when I do the full annual service) and have never had an issue since.

Small minor thing you can do if diving saltwater a lot is put a little piece of rubber inner tube between the backplate and can I find it helps keep the stainless steel aluminum galvanic corrosion down. On a different unit I found that the aluminum would start to get pitted around where the backplate and backplate bolt connected to the can.

Lastly make sure you rinse your first stages well, remember the JJ comes with US4 regs and the O2 side reg diaphragm cap is pointing up so saltwater will kind of "pool" in it so give it a good extra flush after every dive. Oh yeah and you can use some small budge to tie up your fist stages so when you disconnect them there not dragging/resting on the ground, just a pet peeve on mine I hated that the first stages were always kid of resting on the ground when they were not hooked up to tanks.
 
Thanks for your reply and reporting my comments so they're deleted. I welcome your opinions without prejudice, something most contributors fail to do. My top CCRs are Megaladon, JJ and AP. I've heard from JJ users that when diving head down in a mine shaft that the WOB is noticeable. Perhaps you can add credence?

In a head down position WOB is slightly increased but nothing that is unbearable, but its not like you would be in this position for very long. Also the way the JJ's ADV is setup if you tip forward especially on the ADV side all the gas in the counter lungs goes away to the the opposite side causing a slight vacuum on the ADV meaning it fires.
 
That is argued. I don't have a definitive answer. Since I try to get in 2hrs of diving in a day, I might use it again the next day. But I got burned doing that when I missed an unexpected second deep dive because I'd used up the second two hours on the second morning and couldn't get it repacked before the boat left Sunday afternoon.
And then there are divers who will use it past the listed 4hr life.
But a week apart? Are you definitely only going to use it for two hours the next week? Do you have sorb to repack if you need to dive again? Was it tightly sealed in between?
Lots of questions. Me, I don't go past one weekend to the next. That is $10 more expensive. Others do.

My opinion is that there is no problem storing and using your partially spent canisters of sorb for another day. I've done it for years with no issues and I've been diving CCR since 2007. I do a lot of local shore diving that might only be 1 dive for the day, so there is a lot of opportunity to have only minimally used sorb. I dive a couple times a week these days, so it usually does not sit around for long.

But there are a few best practices.
  • Keep a log of your sorb use. I have a printout next to my gear station to track fill dates and dive times. I will do 3 dives or 4 hours maximum on my KISS Spirit which has a pair of 3 pound canisters.
  • Ensure your canister is stored sealed in an environment where it's not too hot or cold. I just keep my unit intact and sealed rather than bagging the canister on a shelf. You don't want the sorb to dry out or get desiccated.
  • I'll keep the sorb sealed for a few weeks to reuse it. I don't think I've used any left idle more than 3 weeks.
  • On dive trips I make a point of dumping, cleaning, and refilling at the end of the day regardless of run time. You don't want to get in a position where you have to rush to refill in the middle of the dive day.

There was a very methodical and scientific study of this practice published a few years ago that show the viability of this approach, and it showed close to zero degradation of partially used sorb.
 
Lastly make sure you rinse your first stages well, remember the JJ comes with US4 regs and the O2 side reg diaphragm cap is pointing up so saltwater will kind of "pool" in it so give it a good extra flush after every dive.

This ^
 
My opinion is that there is no problem storing and using your partially spent canisters of sorb for another day. I've done it for years with no issues and I've been diving CCR since 2007. I do a lot of local shore diving that might only be 1 dive for the day, so there is a lot of opportunity to have only minimally used sorb. I dive a couple times a week these days, so it usually does not sit around for long.

But there are a few best practices.
  • Keep a log of your sorb use. I have a printout next to my gear station to track fill dates and dive times. I will do 3 dives or 4 hours maximum on my KISS Spirit which has a pair of 3 pound canisters.
  • Ensure your canister is stored sealed in an environment where it's not too hot or cold. I just keep my unit intact and sealed rather than bagging the canister on a shelf. You don't want the sorb to dry out or get desiccated.
  • I'll keep the sorb sealed for a few weeks to reuse it. I don't think I've used any left idle more than 3 weeks.
  • On dive trips I make a point of dumping, cleaning, and refilling at the end of the day regardless of run time. You don't want to get in a position where you have to rush to refill in the middle of the dive day.

There was a very methodical and scientific study of this practice published a few years ago that show the viability of this approach, and it showed close to zero degradation of partially used sorb.


100% agree this is basically what I do as well but cant say I have ever kept any for more than a 4-5 days. I'm kind of picky/very particular diver so for me personally I don't like thinking about using several week long stored scrubber. Im sure its fine but sealing up scrubber for more than a week that has your moist exhalation all over it seem like a bacterial breading ground in my mind.

Tip: when I tear down my unit and have a partially used scrubber first thing I do when it comes out of the can is write down the remaining time and date on some masking tape and stick it to my scrubber canister that way there is no confusion when I go to use it latter especially if I have a second scrubbers canisters I am using.
 
100% agree this is basically what I do as well but cant say I have ever kept any for more than a 4-5 days. I'm kind of picky/very particular diver so for me personally I don't like thinking about using several week long stored scrubber. Im sure its fine but sealing up scrubber for more than a week that has your moist exhalation all over it seem like a bacterial breading ground in my mind.

Tip: when I tear down my unit and have a partially used scrubber first thing I do when it comes out of the can is write down the remaining time and date on some masking tape and stick it to my scrubber canister that way there is no confusion when I go to use it latter especially if I have a second scrubbers canisters I am using.

No reason to worry about bacteria growing in your canister. Sorb highly caustic so the PH of 13.5 is too high for anything to grow. Most common bacteria is destroyed at these pH levels.

I clean my hoses, bov, and lungs with steramine but nothing that is downstream of the sorb (like the lungs in my unit) is going to be a growth medium.
 
Don't forget to drain the lung butter from your exhale lung after your dive. It's not necessary but I have a small bottle of Steramine i use to flush my drysuit pee valve when doffing and I pour the remaining 3-4oz/100cc into the loop and down to the counterlung. Doubt it helps much but It makes me feel like less funk can build between proper disinfections.
 
Lot of great info. Thank you for all the tips!

Pool dive Saturday went well and OW dive Sunday went well. Little bottom heavy, so I will definitely need some trim weight to get into the correct position. Overall great dives. Again, I really appreciate the advice.
 
Hey guys, just like the title says. Wooo!!!

So I did my mod 1 course in Feb 2020 and just got settled into being land based again here in Florida.
I am going through the manual and my class material. Going to get in the pool to test everything out before hitting the OW.
Anyone have any suggestions for stuff I may have forgotten in the past year?
I'd appreciate any tips or anything to be mindful of. Just want to cover my bases.
Thanks for the feedback. Cheers!

Congratulations on your new friend! I have been diving my JJ for 5 years and I love it more with every dive. Maybe that's because I'm not certified on any other units, but I am always amazed at how simple, robust and well designed it is. It dives great, always feels very comfortable.

Much good advice has been given, so no need to repeat everything. I have never had an ADV free flow, even head down, so I don't have the shutoff valve, but I know that some have had this problem. Make your own tube weights, I used lead rods with shrink wrap and a pull string epoxyed into the end. I don't usually save sorb, but it seems safe to do that if you keep it wrapped.

And use a written, physical checklist before splashing.
 
Congratulations! It is a good rebreather - get to know it intimately.
 

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