Some commonly asked questions regarding RB diving…
Wednesday, March 7th, 2007I occasionally get asked why I moved to an Rebreather, how I get on with it and how it compares to diving on Open Circuit, so I though I’ll start a Q&A page that may or may not be added to in the future as/when I get asked further questions that I think mightbe of interest to otehrs. The answers below reflect my own personal experiences and perspectives moving from a DIR configured Open Circuit set up to a KISS CCR. Your own experiences are likely to differ and I am not trying to include or exclude any other views, but my own.
Question: Why have you moved over to a Rebreather
1. Gas logistics and economics:
I live in the North of England, but do most of my diving at the south cost in the English Channel. I travel by car to get to the ports. The main ports I visit are (east to west, in no order of importance or frequency of visits) -Dover, Eastbourne, Littlehampton, Lymington, Weymouth, Exmouth and occasionally, Plymouth.
The trips I was doing on Open Circuit as well as now are often on boats without compressor, in places without compressors, or horrendous charges for trimix. As I have my own bank of O2 and Helium at home I found myself sometimes carrying three sets of twin 12s and upto 6 x 7L stages plus a stage for argon in order to do a three day trip and a. keep trimix cost within reason, and b. sometimes to have enough gas for the trip in the first instance. My car suspension took a while tto recover once I had emptied the boot after a dive trip..
After several blownout trips to the south cost in Summer 2004 I found myself in the situation where I had three sets of twin 12s in the garage full of 17/45 and needing to go to my local dive shop to borrow another set of twin 12s so I could get a 32% fill for a local bimble.. this was getting silly.
Then there was the problem of wrong gas for wrong depth, when dive plans changed due to adverse weather and we needed to do something shallower than expected.
Or we were blown out and the next trip planned for the following weekend was going to be shallow. Using 17/45 on a 30m dive is not just expensive, but also incurs longer deco times and requires two stages to be carried etc..
Or the dive went ahead as planned, and the next weekend was booked for trimix again and so I had to tear ass around on a Thursday night to get mixed and filled up again for the Friday. I don’t have my own compressor, and the neighbours wouldn’t thank me for the noise if I did buy one…, plus I don’t really have the time do pump myself and do the mixing.
It all boiled down to logistics and cost in the end. In November 2004 I came across a brand new KISS being sold in the UK - no import hassle, immediate availability, and so I jumped at it.
My KISS is configured as closely as I could make it to mimick the RB80 configuration. I use 2x 7 l steels as drive tanks and carry two bailout stages on deep dives with 50% and 18/40. For longer trips I have a spare set of 7 l tanks plus one set of twin12s of trimix for topups, if I go for a week away.
With that I can last several days of 60-70m diving and still have a reserve, and never less than 150 bar in the tanks at the start of the dive.
The advantages to me are that I do not have to blow off trimix tanks ever to do a shallower dive now. If trimix is available at the site, such as Weymouth, my cost for getting fills is minimal. Cost of sofnolime for a days diving is equivalent to filling one stage of 50% in Weymouth or Portland. I haven’t refilled my 50% stage for over 12 months, and probably just have to use it up one day to keep it fresh.. it has mainly been used to bail out OC divers if they have problems with their deco stages over the last two years…
Although the initial outlay is high, the subsequent costs savings justify the purchase for me. If I hadn’t had the KISS last year I would not have been able to afford to go diving on OC at all. With increasing cost of Helium low gas requirements will be even more of a benefit in the future.
Question: What was the transition like from OC to RB diving?Easy, actually - on the physical side.
More difficult on the psycological side…
1. Physical:
The advantage of the KISS with 7 L upright drive tanks is that is handles pretty much like a set of twin 12s in the water - my buoyancy and trim are not that different than when I was on OC. I can reach my valves and do shutdowns.The weight is behind my shoulders and not in the small of my back.My weight is integrated behind the standard backplate and wing.
The only difference from the front to a Hog configuration are the breathing hoses and mouthpiece (and two contents gauges, rather than one) … and my long hose is bungeed around my neck with a removable connection as it is mainly for myself (an OOA buddy would be given my bailout stage). I could clip it off aka RB80, but decided it got in the way too much.
The main trick was to get the weighting right and the position of the backplate on the unit, and I started off with wayyyy too much lead. Which mean my buoyancy to start with was difficult to maintain, and my gas consumption was horrendous.
Unlike the Inspo, the KISS actually needs less weight than on OC. I used to use 10kg with my twin12s, now I carry 6 kg on the KISS.
The position of the backplate with respect to the unit is crucial.. a bit like the location of the twinning bands on the tanks… too low and you are top heavy and are for ever struggling with trim…
2. Psycological..
…..is a completely diffferent beast.
Trusting the unit to behave (or more importantly.. me being able to cope with whatever might happen) was a bit of a struggle, especially as the standard paragon bail out reg in the mouthpiece is a piece of shit and was freeflowing a lot due to a cookie cut seat when I first got it… ( Jetsam have changed the standard reg to a Mares now..). But I am working with a friend on a DSV that uses an Apex reg - for ease of servicing and reliability.
Any experiences gained on OC were not necessarily transferable to RB diving, and I hate dealing with the unkown.
As always, practice makes perfect and with increasing familiarity with the unit things have become easier.
I wouldn’t say I am fully back to the level of proficiency I had on OC, but I am getting there (March 2007).
I found breathing from the RB mouthpiece took some getting used to and causes me to gag at times - especially at the surface in warm weather… In winter it is fine and I get a lot less cold after a day in a quarry in winter.
The RB breathing air is warmer and moister and does not have the same ‘refreshing’ feel of an OC reg. To me the air intake often has a rubbery taste to it and is not as powerful as an OC reg, more like breathing from a paper bag by comparison.
3. Other issues….
The rear mounted counterlungs of the KISS are great for inwater trim, but not conducive to rolling backwards of a boat…. a sidewards roll is OK, but I tend to prefer to jump in forwards, or move myself over the rib tubes till I face forwards and then do a ‘belly flop’.. not very graceful, but works better for me.Going in backwards compresses the air in the counterlungs and pushes the mouthpiece out of my mouth and air into my lungs - not a pleasant experience - a bit like being jumped on from behind and being left feeling winded…
Swimming on my back on the surface is fine, but sitting stationary in a chop or swell can be unpleasant as the moving waves again can press on the counterlungs. I pay much more attention to the direction of the waves now…
The KISS suffers from a lot of metal into plastic screw connections that make maintenance a worry, and I expect flooded handsets after every battery change (i.e. every 30 hours of diving…). Lukily flooding doesn’t happen too often, but changing batteries or O2 cells are still a nuicance for a regular maintenance proceedure.
Although I don’t need to rush about as much to refill tanks between dives, and can have a quiet evening between diving days when the OC people rush about to get fills I do need to spend a fair bit of time on prepping and cleaning the unit before and after diving trips. Unlike the Insp, the KISS does not need to be dismantled fully each evening, but the prepping before a dive trip might take up to 2 hours if I go for the full clean and repack scrubber operation that I usually do thoroughly before a dive trip. Once on the trip I only change the scrubber each night and rinse out the breathing hoses. I usually do this on the way back into port, so am free of duties for the evening.
The ‘between dive prep’ tends to take less long than prepping my video housing betweeen dives 
I do sometimes feel like chucking the unit in the corner and just strap on the twin12s and jump in.. that usually happens at the start of the season when I haven’t had much chance to dive over the winter…as is the case this year… or when I can’t be asked to prep the unit or clean it… but over all I am quite happy with the KISS.
Question: and (if you still do) how has it affected your OC divingNot at all really. I didn’t use OC at all last year and had to use OC on a training course in the pool in February.. It felt like coming home and my buoyancy and trim just fell into place as if I had been on OC all year. Question: Where do I get my Oxygen and Helium from? The local AirProducts Depot or local dive shops or dive shops at the coast.