By Simon Powell
After a long time of deliberation, I stumped for the DiveMatics DSV. My short list also included the KISS, the Bob Howell and the Nemotech (Filip Krolak) and each was dismissed for the following reasons:
KISS - Lovely small DSV, but I felt the reg would be tough to get spares for in the UK, as it is not a reg I believe you can get over here. Secondly, although I really liked the clever lever action, I felt that a standard rotating barrel would be more robust and preferred having the lever on the front in case of a buddy needing to find it in a hurry.
Bob Howell - Not available new. Did not want to buy a second hand one. Also very bulky in my opinion.
Nemotech - Looks like a lovely DSV, but had heard of lots of problems with delivery and payments.
So a few mails off to Tracy Robinette at Divematics and I had placed my order for their "standard" OC/CC DSV, with Inspiration threads and integrated Oceanicís Omega reg - total cost $750 plus $50 for the Inspiration threaded ends ($800 total).
I could have gone for the version that took a reg of my choosing and fitted an Apeks reg (my favourites), but this was $625, plus $50 for the Apeks adapter and another $50 for the Inspiration ends ($725 total), so I felt that the additional $75 for a second stage was a pretty good deal, and the package looked really neat!
I was travelling to the USA on business, so I arranged to have it delivered to a colleague and collected it from him when I was over there. My business trip was 2 weeks, and I could not wait to get back home and fit it; it was the first thing out of my bag when I arrived back at home, and was on the unit before the first load of laundry was in the washing machine! Having a nice shiny OC solution for my unit also meant that I could ditch the Auto-air that was still in place. I had planned to remove this at the first sign of problems or freeflow, but after a year of faultless performance, it was still in place; but I was unhappy with its bulk. So it was removed and replaced with a standard inflator, which I fitted to a newly shortened hose. I also fitted my MantaBite mouthpiece, which I have grown to like. It takes a while to get used to the mouthful that it is, but after a few dives it was feeling like the norm.
Next, I needed to configure some hoses for the DSV. I wanted to be able to use the DSV with the onboard gas when I was diving shallow and not taking any sideslung tanks but also to plumb it into my deep bailout if I was going deep and carrying offboard gas; this was not a connection that I wanted to change underwater. It was envisaged that it would be an "on-the-boat" choice and so I decided (despite lots of comments to avoid them like the plague - but mainly because I couldn't wait to place an order with Swagelok and wanted the fitting NOW) to get an AP GCS fitting (male one) for the end of the DSV feed hose. I then ran the (now redundant) large bore Auto-air hose over the shoulder to meet this male fitting along the outside of the left counterlung. When running offboard, the male end is directed downwards and connected to another Auto-air hose coming up from the left hand (deep mix) bailout tank. I first thought that I would have to have 3 feeds off my deep bailout reg: Std OC reg, Autoair fitting for DSV std LP hose for manual injector, but decided that I would also not need the standard LP fitting for running semi-closed as I would be able to do this via the DSV (switch to OC, breathe out, breathe in, switch to CC, 4 breaths, repeat) so this meant that it kept my stage regs nice and neat and tidy (which I am a fan of). I also chose to fit a shut off to the reg that I could use in the event of a freeflow. I also chose the hose routing I did because I wanted to have as many hoses as possible coming over my shoulders, rather than underneath.
Here's a front on view showing the exit from the DSV, passing behind the neck to keep the hose tidy
It's almost like a DIR long hose routing ;)
You can also just see the end of the DSV connection going to the offboard whip.
Next one is that offboard connection detail.
And the onboard connection detail
Here's an overall shot with the routing highlighted... onboard
Next onto the testing. I was happy that I had everything in place, so needed to test things out before going off and doing something silly, so off to the NDAC with a couple of others for a splash about. The weekend we chose was also the weekend we were planning to do our bailout practices so it all tied together nicely. I dropped in, and fiddled about with it, switching to OC, CC and back again - lovely. The reg was nice to breathe, if somewhat noisy and bubbly, but that's just OC for you! Took a little while to get used to the position of the newly shortened wing inflate hose (it's amazing how that motor-memory works!), but that soon became natural, and off we went for a deeper excursion, where I wanted to test out the breathing characteristics of the DSV at depth. Down the quarry to ~70m, find a space, and twist the knob - now running 18/35 on OC - damn, it was noisy, and to be honest it felt like quite a hard breathe, but it was equally hard to breathe in as it was to breathe out, so my conclusion is that that it just what OC feels like compared to CCR!
Swam around at depth for a few minutes, before making our way towards the wall and beginning the ascent. Lots of bubbles, lots of noise, and then the unit let out an alarm because the O2 being injected was not being circulated and was sitting in the head next to the sensors, funny how I felt an urge to fix the problem and flush the loop even though I was not even breathing off it! I dropped the SP, and vented some gas from the loop, which moved the O2 slug around a bit and the PPO2 dropped back again, and I continued the ascent. Spent a little bit of time trying out the SCR operation using the technique explained above, which was perfectly manageable, apart from it needing your hands (as opposed to open loop SCR operation - which is still an option for me utilising onboard dil if the DSV is plumbed into the offboard). So I got up to ~20m and still had about 75 bar in the 7L stage, so am now happy that I am able to get from 70m to 20m (switch depth) with a couple of deep stops and a nice steady ascent on a 7L. At this point, I decided to get back on the loop, and conduct the rest of the deco on the unit happy that the DSV worked well, and my OC bailout gas volume is OK at the moment. Surfaced a happy bunny.
So the DiveMatics DSV is a lovely piece of kit and I would recommend fitting one on any Rebreather especially if you are concerned/ paranoid about CO2 (which I am following a hit earlier his year). It's not cheap, but a lovely piece of kit that I'm sure will outlast the rest of my Inspiration. Discuss this article HERE