Info Helium is expensive and deep air is not my thing. -Let's talk about "Big" dives.

[Wibble]

The accounting viewpoint of CCR diving... Too expensive, will never get a ROI.

As usual those who count beans and only think of beans will just result in much farting

Diving CCR is different and a whole lot nicer than open circuit--OK, once you're used to it. It gives flexibility that just doesn't apply to open circuit. The quality of your diving is much better, longer, quieter, no gas anxiety. You dive it with your heart; your head follows with the chequebook.



Just one example. Diving OC trimix, my dive boat had a set of 3 dives I really wanted to do in the 50m/165ft to 60m/200ft range. Unusually, the boat would leave Eastbourne for a dive and return to Brighton for two nights, returning to Eastbourne. I dived OC, so brought two twinsets, three ali80s and two 7 litre 232 bar stages. This was for TWO dives ONLY. Loved the dives, but logistics were a pig requiring taxis and the wife's help to recover the car. I needed two marina trolleys to get all the cylinders back to the car and needed to ask a passer-by to help push it up the slope to the land (quirk of Brighton marina).

Never again I said and always think about that when thinking of the rebreather.

Last week I did 7 days of 60m/200ft to 70m/230ft. Really simple logistics as I only need to fill the 3 litre oxygen and diluent cylinders (+ drysuit air). Those last 2 days minimum, 3 days at a stretch. The Revo needs 1.3kg of lime for one scrubber per day (=5 changes). Bailouts don't get used. Weight is the ~50kg for the rebreather plus two ali80s. Oh, and plus the Blacktip scooter. That was for 7 dives of 2h to 2h45. The gas bill was less than $100, lime was about $50.

On OC the gas bill would have been $1000++ (if I could get the bulk helium) and the dives shorter, noiser, colder (breathing cold gas), more stressful (gas changes) and have critical turnpoints.

 

[Germie]

If you only want to go to 40-45m, then you don't need trimix in most cases. And for sure not a ccr. It is nice to get a trimix cert that you can dive trimix if you really want, but there in a real world you won't do trimix diving on such 'shallow' depths.
A ccr is a nice tool. I also have 2 of these babies in my house. I like them. I am also ccr instructor. But, there is a big big but, a lot of divers use a ccr a couple of years and then sell them again as it is way more work than oc diving.
I never use my ccr on shallow dives I can also do easy on oc. This means that if I am not teaching, 90% of my dives here is oc. Ok, I have over 1000 hours on ccr, so can switch easely, but I alsow ill explain why I choose for oc then.

Disadvantages to think about:
-When diving with friends, they dive oc. Most times are recreational divers. So my divetime is limited to a single tank they use. So there is no need to take my ccr. The lakes here are also soooo shallow that even nitrox is not needed (12m max most times).
-To dive a ccr, I need 20-30 minutes at home to prepare my unit (fill the sofnolime, check everything, etc etc). And I still need to grab the other things like a light, regulator for bo, bo cylinder, drysuit. So the preparation is way much longer.
-After a dive, others drive home, hang their suits to dry (fresh water, so no rinsing needed), and are ready. I have to clean my unit, desinfect, etc. This takes me another 20 minutes.
-If we are on a holiday and others dive oc, they are already having a beer while I am still cleaning my unit.
-If I go diving in Zeeland, salt water, I have to walk 1 time with a bailout and then 1 time with my ccr on my back for dives I also can do on a 7-10 liter single tank. Diving a single tank for these dives is better for you back as you have to climb stairs up and down to reach the water. Also if you bring your bo first to the water, it is laying there without any vision on it. So someone who want to grab it, can grab it.
-Getting fills. I can get air fills at 15km from my house. I have to drive 86km and make an appointment to fill oxygent. This means diving air is way much easier and cheaper. For trimix fills I have to drive further.
-Sofnolime is not free and not cheap anymore. After 3 hours you need to replace it officially. I can dive 24 hours out of a 20kg can, and I pay 130-140 buck for a can of 20kg. So calculate the time per hour by just using sofnolime. 1 air fill is here 4-5 euro.
-oxygen is not cheap anymore here. You pay now around 12-15 euro for a 3 liter fill. This will last several hours of diving, but you also use oxygen on that 8-10m dive, 30-40 bars per hour. Also calculate this
-Cells, around 280-300 euro for 3, you need to replace them every year. So not using your ccr means that you still have costs
-training. You need to do more courses and the courses are most times more expensive. And you need to practise. What I do by not using the ccr in the shallow lakes is not recommended if you are a beginner in ccr diving. CCR diving must be your main diving in the first years.
-It asks more attention. Are you a diver that can do that?
-Travelling with a ccr is harder than travelling and diving oc.
-YOu still need cylinders for bo.
-The promised shorter decotimes are not giving you that big difference. Do some plans oc and ccr. Oc with the right gases of course (so deco on ean, or ean32 at 30m).

But, there are also a lot of advantages:
-silent
-If you cannot fill somewhere, you can dive long times with just some 3 liter tanks. For a week cavediving with no fillinglogistics, a ccr is a must. Oc is impossible
-you go easier deep or longer. Trimix is still expensive, but there is a big diffence between a 3 liter fill and a 24 liter fill.
-bailouts can last for years if you are lucky. I have bailouts here that are there for already 10 years. So the cylinders are out of test now, but the fills are still there. When you are unlucky, you have to use them of course. I have done 1 real bailout due to a co2 hit in the 11 years of ccr diving, so this means the unit itself is trustable.
-less weight then a twinset
-For photography, you can get closer to some animals. I have made a picture of mating tench with my sidemount ccr in only 2m deep water which would never be happen when diving bubbles.

So I use my ccr a couple of times a month while minediving. But I don't use it on the shallow dives in the lakes here.
If I was only diving 40m depth, I would never switched to ccr. But I also do dives over 100m sometimes and long cavedives, and then there is a benefit of using a ccr.

The price of 8000 is not necessairy, you can find used units which are good for 3500.

Before I bought a ccr I did 4 100+m dives a year and I calculated a breakeven point of 8 years if I calculated my investment of the ccr (second hand 4000 euro) if it would never broke and the heliumprices stayed the same and 4 100+m dives a year. My ccr had some problems with buttons, so I had repaircosts, and I did not calculate the prices of extra courses (MOD1 and MOD3, I could skip MOD2 as I already was an oc trimix diver). If I took these costs into the calculation, there would never be a break-even point. But since I dive a ccr, my diving has been changed. It is easier to go deep now. I always have cylinders with 6/72 at home, so I always have trimix available for dives between 50 and 150m if I want to go. I also have bailouts, so don't need to fill before going to a divesite.

Yes I am an ccr instructor and yes I like a ccr. But I am also the person that not only want to tell the haleluja about ccr's, but also the disadvantages. But don't buy it because of the 'cheaper diving'. There is no cheap technical diving. Buy a ccr as a usefull tool.

 

[Wibble]

If you only want to go to 40-45m, then you don't need trimix in most cases. And for sure not a ccr. It is nice to get a trimix cert that you can dive trimix if you really want, but there in a real world you won't do trimix diving on such 'shallow' depths.

Of course, with a rebreather, every dive is a helium narcosis-free dive.

Open Circuit logistics is a pig having to get the cylinders refilled with the right gases. On CCR you just use the old OC twinsets as gas banks (Helium, Oxygen, Air) and you're good to go for months of diving. OK, the gas bill will be a bit frightening, £200/$260 for the last bank topup!

 

[Dave Whitlow]

If you only want to go to 40-45m, then you don't need trimix in most cases. And for sure not a ccr. It is nice to get a trimix cert that you can dive trimix if you really want, but there in a real world you won't do trimix diving on such 'shallow' depths.
A ccr is a nice tool. I also have 2 of these babies in my house. I like them. I am also ccr instructor. But, there is a big big but, a lot of divers use a ccr a couple of years and then sell them again as it is way more work than oc diving.
I never use my ccr on shallow dives I can also do easy on oc. This means that if I am not teaching, 90% of my dives here is oc. Ok, I have over 1000 hours on ccr, so can switch easely, but I alsow ill explain why I choose for oc then.

Disadvantages to think about:
-When diving with friends, they dive oc. Most times are recreational divers. So my divetime is limited to a single tank they use. So there is no need to take my ccr. The lakes here are also soooo shallow that even nitrox is not needed (12m max most times).
-To dive a ccr, I need 20-30 minutes at home to prepare my unit (fill the sofnolime, check everything, etc etc). And I still need to grab the other things like a light, regulator for bo, bo cylinder, drysuit. So the preparation is way much longer.
-After a dive, others drive home, hang their suits to dry (fresh water, so no rinsing needed), and are ready. I have to clean my unit, desinfect, etc. This takes me another 20 minutes.
-If we are on a holiday and others dive oc, they are already having a beer while I am still cleaning my unit.
-If I go diving in Zeeland, salt water, I have to walk 1 time with a bailout and then 1 time with my ccr on my back for dives I also can do on a 7-10 liter single tank. Diving a single tank for these dives is better for you back as you have to climb stairs up and down to reach the water. Also if you bring your bo first to the water, it is laying there without any vision on it. So someone who want to grab it, can grab it.
-Getting fills. I can get air fills at 15km from my house. I have to drive 86km and make an appointment to fill oxygent. This means diving air is way much easier and cheaper. For trimix fills I have to drive further.
-Sofnolime is not free and not cheap anymore. After 3 hours you need to replace it officially. I can dive 24 hours out of a 20kg can, and I pay 130-140 buck for a can of 20kg. So calculate the time per hour by just using sofnolime. 1 air fill is here 4-5 euro.
-oxygen is not cheap anymore here. You pay now around 12-15 euro for a 3 liter fill. This will last several hours of diving, but you also use oxygen on that 8-10m dive, 30-40 bars per hour. Also calculate this
-Cells, around 280-300 euro for 3, you need to replace them every year. So not using your ccr means that you still have costs
-training. You need to do more courses and the courses are most times more expensive. And you need to practise. What I do by not using the ccr in the shallow lakes is not recommended if you are a beginner in ccr diving. CCR diving must be your main diving in the first years.
-It asks more attention. Are you a diver that can do that?
-Travelling with a ccr is harder than travelling and diving oc.
-YOu still need cylinders for bo.
-The promised shorter decotimes are not giving you that big difference. Do some plans oc and ccr. Oc with the right gases of course (so deco on ean, or ean32 at 30m).

But, there are also a lot of advantages:
-silent
-If you cannot fill somewhere, you can dive long times with just some 3 liter tanks. For a week cavediving with no fillinglogistics, a ccr is a must. Oc is impossible
-you go easier deep or longer. Trimix is still expensive, but there is a big diffence between a 3 liter fill and a 24 liter fill.
-bailouts can last for years if you are lucky. I have bailouts here that are there for already 10 years. So the cylinders are out of test now, but the fills are still there. When you are unlucky, you have to use them of course. I have done 1 real bailout due to a co2 hit in the 11 years of ccr diving, so this means the unit itself is trustable.
-less weight then a twinset
-For photography, you can get closer to some animals. I have made a picture of mating tench with my sidemount ccr in only 2m deep water which would never be happen when diving bubbles.

So I use my ccr a couple of times a month while minediving. But I don't use it on the shallow dives in the lakes here.
If I was only diving 40m depth, I would never switched to ccr. But I also do dives over 100m sometimes and long cavedives, and then there is a benefit of using a ccr.

The price of 8000 is not necessairy, you can find used units which are good for 3500.

Before I bought a ccr I did 4 100+m dives a year and I calculated a breakeven point of 8 years if I calculated my investment of the ccr (second hand 4000 euro) if it would never broke and the heliumprices stayed the same and 4 100+m dives a year. My ccr had some problems with buttons, so I had repaircosts, and I did not calculate the prices of extra courses (MOD1 and MOD3, I could skip MOD2 as I already was an oc trimix diver). If I took these costs into the calculation, there would never be a break-even point. But since I dive a ccr, my diving has been changed. It is easier to go deep now. I always have cylinders with 6/72 at home, so I always have trimix available for dives between 50 and 150m if I want to go. I also have bailouts, so don't need to fill before going to a divesite.

Yes I am an ccr instructor and yes I like a ccr. But I am also the person that not only want to tell the haleluja about ccr's, but also the disadvantages. But don't buy it because of the 'cheaper diving'. There is no cheap technical diving. Buy a ccr as a usefull tool.

Curious post and so much I disagree with but if your choices work for you then that is fine. and I wish you well.

I moved from single to twinset to dive longer, and then deeper happened, and then I saw narcosis and found helium, and 14 years ago, whilst at 65m near Malin Head (U2511) on my twin 16s I watched my buddy finning away creating a video, and contemplated my 'what if' options. Assuming my buddy would not notice anything I considered the outcome of a low pressure failure and wondered how much gas loss might occur, and whether I would retain enough gas to reach my next gas switch (about 10 minutes finning and 25 metres shallower), and concluded I wasn't sure. I didn't like that answer so when I got home I sent an email to an instructor and 6 weeks later I commenced my CCR course (with recreational trimix) and retain the unit I trained on (with upgrades). I now mostly dive CCR, with a variety of bailouts, but still dive single tank for local shore dives and shallow stuff where a single tank makes sense.

After discussions with other CCR divers I did experiments with air at depth and found my experience of narcosis began at around 25m and was progressive. Being incompetent at depth seemed a poor life choice so I concluded my future diving should respect those observations and I only dive deeper than 25m with some helium in the mix.

At no point did I consider, or care, about the costs of CCR vs. OC as being a cash rich casualty seemed to lack appeal.

There are no savings in choosing CCR and it does require a lot of extra equipment (multiple bailouts, numerous 3l cylinders, 50l bottles of helium and trimix, bottles of oxygen, booster pump, trimix analyser, and more) but overall the experience is better.

I have only one life so better is more important than cheaper.

 

[johndiver999]

CRC Cash Rich Casualty.-- liked that one

 

[rx7diver]

... on my twin 16s I watched my buddy finning away creating a video, and contemplated my 'what if' options. Assuming my buddy would not notice anything I considered the outcome of a low pressure failure and wondered how much gas loss might occur, and whether I would retain enough gas to reach my next gas switch (about 10 minutes finning and 25 metres shallower), and concluded I wasn't sure. ...

@Dave Whitlow, determining the minimum amount of gas, for your choice of OC gear configuration (isolation-manifolded BM doubles, independent doubles, etc.), to relatively safely make a planned 65m dive is straightforward. I'm not sure why you concluded that moving to CCR was indicated. Can you elaborate?

Did I misunderstand your post?

rx7diver

 

[SelfDiver]

It is nice that all of you are talking about the CCR option.
I looked at the top of the page and this just happens to be the "Technical Diving" forum.

Rebreather Diving

Find out everything you ever wanted to know about rebreathers.

scubaboard.com

That is the correct forum for CCR stuff.
The point was to encourage newer tech diver to practice for the BIG dives in shallow depth so that they are comfortable when they eventually pony up the cash to 80m and 100m. It is mostly to stay current on logistics.
I like OC or CCR. I like twinset and sidemount and support divers and DPVs.
All of this is fun to me.
How do you get all that gear to the surface of the water? That is not a tech diving certification question. No amount of S-drills and valve drills will prepare you for a successful dive if you can't get to the water.
The most experienced cave diver will have to think a bit when diving from a boat. It is outside their regular experience.
Shore diving brings other considerations.
Even when the water portion is easy, Logistics around the dive can be difficult.

One thing I learned from this thread is that Learner Diver got banned. His questions were so bad, that I was hoping to see more. Like an accident on the highway or those "Fail" videos. I fell for his trolling and responded in earnest. I feel duped,

It inspires me to open a new thread on "Good diver vs. Good-natured diver" as a buddy.

 

[Dave Whitlow]

@Dave Whitlow, determining the minimum amount of gas, for your choice of OC gear configuration (isolation-manifolded BM doubles, independent doubles, etc.), to relatively safely make a planned 65m dive is straightforward. I'm not sure why you concluded that moving to CCR was indicated. Can you elaborate?

Did I misunderstand your post?

rx7diver

I was diving isolation-manifolded double 16l cylinders and planned the dive to arrive at the switch point with a lot of gas and was getting complaints on the boat that I wasn't using enough gas. (even in 2010 helium wasn't cheap). However, in that moment of doubt, I wondered what volume of gas would remains after a LP hose fail and my best shutdown efforts at that point in the dive.

Whilst it didn't happen I decided I preferred the idea or a primary dive system and a known quantity of bailout gas as a reserve. When I got the £500 gas bill at the end of the week (this was 2010) my decision was reinforced. I have never regretted that decision.

 

[rx7diver]

I was diving isolation-manifolded double 16l cylinders ...

Thanks, @Dave Whitlow. Hmmm. It seems that those on the boat didn't believe that your RMV rate would allow the ~7,400 (= 2 * 16 * 232) liters, or ~260 cu ft, of gas you were carrying in your isoation-manifolded doubles to be of sufficient quantity (including emergency reserves) for you for this planned 65 meter, or ~210 fsw, dive.

Or maybe they were thinking that the emergency gas you were carrying wasn't enough to support your dive buddy in the case of an emergency situation. If everyone else is diving 19 liter cylinders (say), but you are diving 16 liter cylinders, then gas matching must be carefully done.

In general, a LP hose failure shouldn't pose a too-challenging situation. This is where valve shut-down training applies. At any rate, you have allowed for such a failure when you planned your dive, and, so, your remaining gas "is" enough to get you (or you and your buddy) back to your first deco gas. Is this how you were planning dives back in 2010? If there had been any doubt about being able to shut down the isolator, then an independent doubles configuration (rather than a manifolded doubles configuration) would have been a "better" choice (perhaps).

But I do understand about the comfort of having an "unlimited" amount of gas when using a CCR, and I do understand about the concerns about the crazy costs of helium mixes when diving OC.

rx7diver

P.S.: I don't use metric. So, please correct my calculations if you see any error(s).

 

[Germie]

I never heard that oc divers don't buy enough gas. In Germany it started: they said they don't earn enough from ccr divers, so that made a minimum price for a fill of oxygen or trimix. They said they have to screw in the same hose for filling, so it is a difference if that action will earn for them 7 bucks or 15 bucks or only 3 bucks. Now you see it sadly everywhere. I have invited to screw the hose in so it was not work for them.

But I have heard that people said I cannot do that dive oc with just a twin12. I have done 110m with 17 minutes bottomtime with 'just' a twin12 as backgas. But the backgas is not the problem. It are the travelgases and decogases when you make the calculation right. This is why you have to consider safety divers for it. But this does not change on ccr, they are also limited in the travelgases and decogases in case of a real bo. This also means that the big boy talk about 50-60m on 100m with a ccr is ********. The deco will be endless and you cannot carry your own bo anymore.

But I am low on consumption. Very low. For the cenotes in Mexico we have a small group of divers and if someone wants to join, we first do a dive to see if the gas consumption is very low (under 12 liter per minute). If not, then they cannot join.

On guided dives I always ask them what about big consumers as I am a low consumer. I don't want to pay for half dives. Last year on a private guided very expensive (102 euro) black water dive there was said max 60 minutes. After 45 minutes the guide only had 50 bars left and wanted to get out. I signed no, you still have gas, and I have paid for a 60 minute dive, so he had to stay. He got a little bit nervous, but he did not had his tank drained completely (then he was allowed to get up). We finished the dive with in his tank only 10 bars and I had still 80 left. But I had paid for a dive and a guide for 60 minutes, then you have to make sure you can 60 minutes as a guide. Of course I would have let him out if he was really to zero and would have shared gas, but no, with 50 bars he could stay as I paid for it. This is also an advice if you act as a guide and you promise customers 60 minute dives. Make sure you can do them also. There will be a moment that you have a customer that is a low consumer and then that customer doesn't want to go out (of course not, he also pay for his dives).
In Egypt on single tank shore dives without a guide they looked strange when we wrote 120 minutes as divetime on a single tank. But we did. The first times they checked if we had some gas left in the tanks (I am not baby, why don't you trust certified divers? This never happens when you rent a car. And remember, also low consumers cannot stay under water without gas, so if they come up relaxed, tanks are not empty). But then they just accepted after 2 days that our divetimes were not average.

A cave diver on a boat is not that strange. There are places in the world where cave dives are boatdives like Sardinia or Khao Sok Thailand. So it is not true to state that cave divers don't have experience in boat diving. I am a cave diver, but also do wreckdives. I have done all kind of dives from a boat, but the most difficult are the ones in sidemount most times. A twinset or ccr is easier. A twinset or ccr doesn't differ from each other, in both cases you have some stages with you. What is on your back is not different for gearing up. Only the pre dive checks with ccr are different.