When Marci and I switched to CCR (also Sidekicks) a few years ago we each had:
- two sets of back mount doubles
- a set of LP 85 side mount doubles
- a set of steel 72 side mount doubles
- a set of LP 45 side mount doubles
- two AL72 stages
- three AL 80 stages
- an AL30, and
- anAL 6 and an AL 13 as dry suit inflation bottle.
(plus three more AL 80s out on loan)
After our CCR conversion we each have:
- a pair of LP 85s for our dil/out bottle (with a spare), and on occasion, side mount doubles
- a pair of steel 72s for side mount doubles
- a set of LP 45 for open water CCR dil/out and for really small passage side mount doubles
- two AL72 stages for CCR bailout (I prefer them over the AL80s)
- an AL 80 stage for CCR bailout
- two O2 clean AL 80s with O2 (for cascade filling our small O2 bottles on trips)
- an AL30 for O2 bailout
- three AL13s for O2 CCR bottles.
(and three more AL 80s still out on loan)
We initially kept the back mount doubles for offshore wreck dives, but we eventually sold them all. We don't do deep offshore dives much and if we do we'll use the side mount rebreather in one of two ways.
When we went to CCR, we bought a pair of Faber 15s to start with for O2 bottles, but I found I preferred the AL13s, so we bought four more (a total of three AL13s each).
The net change in tanks then came down to getting rid of the LP 95s and buying some AL 13s. I could probably sell off the steel 72s, but I really like steel 72s and I still use them for dil/out on OW CCR dives.
Our CCR versus OC patterns are similar to Gareth's. We'll dive OC on pretty fish dives, and I'll dive OC if I am working with a new OC diver. Other wise, I just prefer OC, and the added cost is minimal over the long term.
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On large passage dives, I'll carry an AL 72 stage for redundant diluent and additional bailout. However, all our bailout stages are also configured with a QD fitting on the second stage so they can be used as redundant diluent. We also have QDs on the second stages on our LP 85 dil/out bottles with a 5' hose so that we can also use that to share diluent if needed.
On small, tight passage portions of dives where taking an AL 72 or AL 80 stage isn't a viable option, I'll carry a smaller redundant diluent bottle - as small as an AL6 in shallow systems with little or no depth change and no need to descend to exit. Some folks absolutely lose their **** at the idea of using an AL 6, but it's just redundant dil not redundant everything, and within the above parameters it's more than enough for an exit. An AL19, and AL 30 or and AL 40 all work well when progressively more redundant diluent may be needed, and if you're diving a deep system, you're going to have one or more stages with you anyway for additional bailout, so the redundant dil is covered.
For offshore dives with no deco obligation, a LP 45, LP 46 or LP 50 works really well as it smaller and lighter than an LP 85, AL 80 or AL 72, and makes it easier to navigate exit gates and boat ladders while it still provides more than enough bailout gas. For deep offshore dives, I kept my old Nomad and with a set of stabilizing plates and bands it works well to carry a pair of back mounted tanks for bailout. With a pair of back mounted AL 80s, you have 154 cf of bailout gas with room for bailout O2 staged on the left side, with the Sidekick on the right. You end up being no worse off coming aboard a boat than an OC diver doing a 4 bottle dive.
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In practice we'll drop a stage about every 800' in 100' deep cave and about every 1100' in 60' deep cave. The good news is that you never use them, and you can take them in a system and then leave them in place, or on some cases reposition them slightly but still leave them in the system until you are done diving there. Consequently, you need fewer stages than OC, even when doing larger dives. Where more stages come in handy is when you are doing trimix dives where you will be using different mixes. Since you never actually use them unless you have an emergency your fill costs are pretty much a one time deal.
With a pair of LP 85s we can keep one ready to go with trimix diluent, and then only have to top it off with 600 psi or so after 2-3 dives.
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I don't know that we carry all that much less weight or bulk on a CCR trip compared to an OC trip, once you consider sorb, spares and associated CCR support stuff. We also don't like paying minimum fill rates to top off an AL 13 with 6 or 7 cu ft of O2, so we will bring a pair of O2 filled AL80s and a transfill whip. We could save weight and bulk, but we're cheap, and it's nice to be self sufficient. Before we had a booster we'd also fill the AL 80s before heading home to provide O2 at home since the local shop didn't have a booster either. One shop in N FL didn't like filling our AL 80s (time needed to boost, etc) but we just used another shop for that.
We do carry sorb in kitty liter jugs. The large size will cover three fills and 15-18 hours of diving, and a pair of those is more convenient on a 3 day trip for the two of us than a 44 pound keg of sorb.
*, and for sidemount cave diving when I can get a sphere, the 3l will become dil. Sidemount on the other side.
