Rebreather Purchase question

[shamre]

I am seriously looking at purchasing a rebreather and the accompanied training. I was just wondering which rebreather is best. I would be looking at a CCR system. Any info on various models and benefits would be helpful. 8)

[Inspirationdiver]

Have you already weighed the benefits of SCR vs CCR? SCR units still have a lot of the advantages of a CCR but are less complicated. That being said, I personally chose to go with the Inspiration. There are only a couple readily available CCR units on the market and the Inspiration is by far the most common. I don't really know what your background knowledge is on rebreathers so I don't really know where to start. Do you have any specific questions about differences between models?

[ghosch]

I agree with ID. Having owned both a SCR and (currently) a CCR the SCR was a great tool for recreational dives. Easy to set up and understand, less expensive, simple operation, great to travel with. If I could afford it, I'd own both!

You really need to think about things like:
1. Why do I want a rebreather?
2. What type of diving to I do?
3. Do I want to travel with it?
4. How much do I want to spend?
5. What features are most important to me?

If you asnwer those questions, one of the multitude of options will probably become a clear choice.

Next time GUDC has a rebreather symposium, you should check it out, there will be a lot of people there who can talk about the different units.

Also, I'm sure you'll see us around the Lakes this summer (Wazee, Crosby, Superior, etc.) feel free to ask questions, most of us are more than willing to drone on for hours about how wonderful our rebreathers are

[igotoofar]

After talking with the folks over at GUDC, I decided the CCR was nice but the SCR seemed to be a better fit for me.

[shamre]

The way i understand it, scr are only good for shallow water diving. But if you are going below 150' you would need to dive ccr. Is that correct? ???

[Inspirationdiver]

CCR's are much more efficient with gas consumption, so you can make much longer dives on less gas. They also can easily be used with trimix. Some people have modified their SCR's to use trimix with them but they don't work quite as well. Another advantage of CCR's over SCR's is constant PO2. This gives you the optimum breathing gas at every depth, which can significantly shorten your decompression time.

[ghosch]

I don't think it necessarily safe to say that SCR's have a specific depth limit, it varies by unit. The Dolphin for example (which is the only SCR that I have used) technically has a depth limit of 132' (it's based on the mod of the source gas). Other units probably have different limits.

[Freedive WI]

Some people have modified their SCR's to use trimix with them but they don't work quite as well.

How do you do that? Is it just a matter of filling up the dirve bottle with mix and using the 32% sonic orifice, or do you get a custom made orifice as well?

Just wondering, ???


Jon

[Chuck_Northrup]

Jon,

It is generally agreed upon in the rebreather community that the "perfect rebreather" has not been invented yet. You need to look at each unit as a specific tool for a specific dive. Unfortunately what one person sees as a benefit another will likely see as a disadvantage so there never will be a "perfect rebreather" for everyone.

Rather than wait along for this enigmatic technology to develop some ambitious RB divers have taken it upon themselves to create their own rebreathers (modifications and homebuilt systems). It is not something as an instructor that I would encourage or endorse, but a lot of people have done it. Just check out and go into the modified (special) or homebuild sections.

The main reason it happens so frequently is that the process is not overly complicated and some people have an inherent need to mess with things : I believe you are certified for the Dolphin and should have a basic understanding so I will use it as an example.

#1. Block the sonic flow orifice so that you will have diluent introduced to the system through the automatic diluent valve only (ADV)

#2. Add a bottle of O2 with appropriate 1st stage and a metering device to deliver O2 just below your metabolic rate. You will need a manual override for O2 to maintain quasi-constant PO2 (it would work on a decaying PO2)

#3. Add a 3 sensor PO2 monitoring device because you are now diving CCR and 1 sensor is no longer acceptable.

This is basically an extrapolation of Gordon Smith's KISS rebreather concept. You can find out more information at
There are as many different ways to modify a rebreather as there are people willing to chop them out. If some of the information above is a little vague I apologize but I want to stay non-specific so that people do not think I am in favor of these practices Hope this info helps.

Chuck

[Freedive WI]

Thanks Chuck, that answers the question.

I have poked around on those sites and seen some of the modifications that people have done to their units. I was thinking that there was a short cut through the whole system-like just using some kind of premix in the drive bottle and using a stage bottle of 50% to get to safe PP02 depth and back again. Not that I would ever try any of this stuff, but I still find it interesting what people come up with. It sounds like they do something more involved by adding extra bottles and regulators to their existing systems.

Maybe you could answer a question I posted under a different thread. The RB80, as I understand it, is designed to be a constant F02, instead of a constant P02, rebreather. Didn't the "Gator" or the "Frog" have a similar design? Did they ever make it to market?

Thanks,

Jon