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heidihart88:
- Get a drysuit that fits. This is key. It will make it very easy to manage the bubble inside your suit.
- Go with a drysuit that has a soft booties (crushed neoprene or other) that you wear rockboots over. This minimizes air pooling in the feet. With this kind of setup, it's nearly impossible for air to be forced into your feet and your boots/fins to pop off. It's not any fun to be in the water without fins. (Fun for your buddies to watch you, I guess.)
- Under most circumstances, your exhaust valve should be like the TV infomercial for a mini-rotisserie oven -- set it and forget it! Many people leave theirs completely open. I'll close mine down completely as I descend if I want to dive with more air inside the suit. Sometimes I'll tighten it down while I'm in the surf zone on a shore dive.
- During ascent, vent early and vent often. Always stay ahead of the expanding air inside your suit.
- I don't want to get into the debate of which buoyancy control device to use. You should experiment with both methods (drysuit only OR BCD + enough air in drysuit to offset squeeze) and see what feels right to YOU. As has been pointed out already by WebMonkey, drysuit exhaust valves are designed to vent faster than the inflator valves can inflate...provided that the exhaust valve is the highest point on your body AND nothing is obstructing air from getting out. As for managing suit squeeze, it should never be so tight that it's uncomfortable or restricts your movement in any way. Finding the minimal amount of air inside the suit to offset squeeze at a given depth is something that you'll have to play around with. Feel free to add and subtract air to the suit as necessary. For me, I found that the learning curve for operating a drysuit was similar to learning how to drive a manual transmission car. YMMV.
- Test the drysuit inflator and exhaust valves during your pre-dive checks. After I zip up my drysuit (but before I slip into my BCD), I'll generally crunch down into a ball and ensure that air can pass easily through the exhaust valve. Then, when I stand up, I'll break the neck seal slightly with my fingers to allow air to enter the suit again. That just makes things more comfortable for me as I go about setting up the rest of my gear. After I don my rig, I'll connect the inflator hose to my drysuit inflator valve and then give it a couple of short taps to verify that it starts and stops.
All drysuits are not created equal. One of the biggest decisions to be made is the type of suit material. For you, I'd recommend a bilaminate or trilaminate shell suit. It's adaptable to many different water temps by adjusting the undergarment. It dries quickly. It's light and very portable. It's relatively easy to patch holes in the material. Comparing a crushed neoprene suit to bilam or trilam, you'll find that you probably need to wear much more lead with the crushed neoprene suit. That's the trade-off for better inherent thermal protection and a longer-lasting, more robust suit.
You should take a look at the Whites Fusion suit. It's a great value for the price and its design (outer lycra skin) helps to evenly distribute the bubble inside the suit. Test dive it. You'll love it. (N.B.: I have no relationship with Whites. They simply make a great product.)
Keep in mind that rental drysuits are like any other piece of rental shop gear -- used and abused. Don't worry. You'll take care of your inflator and exhaust valves MUCH better than any rental suit. FWIW, if you do purchase your own suit, in most cases you should be able to get several hundred dives before you have
ANY issues with the inflator or exhaust valves. I believe that Si-Tech covers their valves with a manufacturer's warranty of 2 years from original purchase date. If any valves give you any trouble, Si-Tech will replace the part with no questions asked. Apeks is the other major manufacturer of inflator and exhaust valves. I believe that the company has a similar warranty.
Sorry that you had so many issues with the drysuit dives. Perhaps you should consider doing the AOW dives in a wetsuit. If you haven't done the type of diving that an AOW entails, it might be too much to burden yourself with another buoyancy control device...especially on a fairly deep dive during which you should be getting acquainted with nitrogen narcosis. Besides, it sounds like your not at all sure whether a rental drysuit won't malfunction again. Take things one step at a time. With experience, I think you'll find that drysuit diving is both comfortable and safe.
Good luck with everything.