Dry Suit with Auto Dump Valve

[jamesadele]

Hi guys, new member here.

After a lot of searching and a lot of contradictory information I am still trying to fully understand how to correctly achieve neutral buoyancy in a neoprene drysuit with automatic shoulder dump.

Some say open some say it should be closed some say half others say back a few clicks. While I have read the info on how these valves work I am still a little confused by some of the info out there.

From what I understand at this point would I be right in saying that you descend with the valve open and try to achieve neutral buoyancy at the desired depth. if you cant because air is being released then you notch it back one click and try again,,,, rinse and repeat?

If that's right I get it, if not please help me out.

The second thing is if you accidentally put too much air in I understand you can press the valve to release some air and thats fine, however others have written raise your elbow or roll slightly and this will dump air. If this is so it doesn't really fit in with what I understood the valve to be doing. As I understand it lifting your arm would not release air like it would with a cuff dump because the air volume hasn't changed. Is there another aspect to the operation of the valve that I am missing, and if so how do you prevent accidental dumps of air when moving around?

OK so the third thing I think I understand is that when you have got your buoyancy and valve adjusted as above, it should be fine to ascend allowing the valve to dump expanding air automatically but you can override it with a quick push of the valve to slow your ascent if it gets to quick.

I appreciate any help you can give me so I can better understand the suit operation. The suit in question is a very good O Three thing and the reason I need very specific advise on it is that i am doing an open water course with my wife, and all of us except her have the shell style suits but they haven't one to fit her properly. We did the first 2 dives but she had terrible trouble getting her buoyancy and was all over the place. I suspect that a very tight weight belt trapped a lot of air in her legs on the first dive as she really had no chance of controlling her movement and found it very difficult to move her legs and floating away. The second dive was much improved and she said the suit squeezed her legs on this dive as well which she said didnt happen the first dive. Anyway the second dive was an improvement but we didn't have much time to play around with the suit and understand what was happening with the valves etc and she was still up and down. This could be due to the valve letting air out but we didn't notice because it was all new and frustrating to her.

I know most of you will be aware that there is a lot to get through in your open water dives so if she can nail her Neutral Boyancy we may get time to have a good swim round and I really want her to get a bit of time exploring the open water and enjoying it this next dive. So like I say any advice or insight in to the best practice with a suit like this would be most welcome.

All the best

James

 

[BRT]

Raising your arm makes the shoulder higher. If it is set so it just needs a little more pressure to open raising your arm will dump air. You can raise your arm straight up, which lets the arm fill air from elsewhere in your suit, and then lower the arm kind of wrist first and it will dump if the valve isn't too tight. On the way down I tend to tighten the valve down a little to prevent dumping and then as I think about working my way up I loosen it.

 

[fire_diver]

Adjusting the dump valve won't matter on descent. You will be adding air to relieve much of the squeeze you feel as you go down.

 

[decompression]

A big point, the drysuit is not for buoyancy (primary), it is there for thermal protection. A drysuit makes a horrible BCD. Adding air is to eliminate squeeze and keep you warm.

I teach all my open water classes in drysuits. I find it easiest for them to keep the valve open at all times. With proper trim the suit stays inflated and a simple raising of the arm or wrist can exhaust air.

Addressing your wife's issue, ensure that the suit is void of air before starting the dive and only adds small amounts of air, again only enough to reduce squeeze. Feeling and anticipating where the air will move becomes natural after awhile.

 

[fire_diver]

Sorry, I forgot to address for someone wholly new to diving. In cold water, you wear thick thermal clothes underneath to stay warm. When you first get into the water you have WAAAAAY too much air in the DS, so most people just "burp" it at the neck seal to remove the excess. As you go down the pressure is going to squeeze the suit tighter and tighter until you feel shrink-wrapped (if you let it go too far). This also makes you cold because all that thick under-clothes is now squashed thin and not working very well. You fix both problems by putting short taps of air into the suit. You want to dive with a small amount of squeeze. Big air bubbles like to move around and if you have too much you can get it trapped in your legs/feet and feel like a dork fighting upside down to get right. Big air bubbles in the suit also mean you need more lead which means it's harder to constantly try to make adjustments for buoyancy.

dump valve tight/loose is personal preference, and is really a small piece of the entire DS buoyancy game.

 

[Storker]

A big point, the drysuit is not for buoyancy (primary), it is there for thermal protection. A drysuit makes a horrible BCD. Adding air is to eliminate squeeze and keep you warm.

I teach all my open water classes in drysuits. I find it easiest for them to keep the valve open at all times. With proper trim the suit stays inflated and a simple raising of the arm or wrist can exhaust air.

I prefer diving with my shoulder valve wide open, but I won't recommend that to anyone and everyone. I've got two drysuits: A snug neoprene suit with only enough space for thin wool underwear, and a trilam suit with enough room for a thick winter undergarment. If I'm wearing my trilam suit, I have to close the valve before ascending vertically (or going head-up in the water, e.g. for taking a picture). If not, I'll lose my comfort air through the shoulder dump valve and become negative shortly after going head-up. And I'm using my wing for primary buoyancy control, but with my weighting I usually only have a little air in my suit and none in my wing at the end of my dive.

dump valve tight/loose is personal preference, and is really a small piece of the entire DS buoyancy game.

This.

IMO, it's a question of how lazy you are. With the shoulder valve open, you don't have to press it to dump air (lazy diver). With the shoulder valve closed, you'll have the minor inconvenience of having to use your right hand to press the valve to dump air, but you'll have real redundant buoyancy in any position (horizontal, head up, feet up or anything inbetween). Anyway, I prefer to close my shoulder valve after surfacing, to ensure redundant buoyancy.

---------- Post added August 12th, 2014 at 06:45 PM ----------

i am doing an open water course with my wife [...] she had terrible trouble getting her buoyancy and was all over the place.

That's not uncommon. Learning buoyancy control isn't that easy.

On the bright side, by taking your OW in a DS, you'll be ready for DS diving from the get-go. I've got the impression that it's generally regarded as difficult to learn DS diving if you certified wet. A little extra frustration now may well save you more frustration later

 

[Phil_C]

Hi James, as a fellow drysuit diver I can understand why you are confused. But before deciding how to use the valve and dive your drysuit (DS) you need to decide if you will use the DS for buoyancy or just for warmth. You will find people argue endlessly about which is right or wrong, I use the DS for warmth and no more, if I need to adjust for buoyancy otherwise I use my wing (or BC if that is what you are diving). Doing it this way you have two air volumes to manage, but if you set the auto dump as described below that is not a problem.

So if you are going to use the DS just for insulation then the best way I have found to set the auto dump on my drysuits is to do the following.

First - have the valve open when you don the suit, when you have got it on and zipped up cross you arms across your chest and squat down curling your body over your knees, you will feel the excess air being expelled through the valve and you will deflate a bit (so to speak!). This will help to get a lot of the excess air on your drysuit out and normally prevent you having to 'burp' air out of the neck seal as mentioned above.

Then close the valve, enter the water when fully kitted and check you still don't have too much air in the suit, if you do then raise the valve and depress it to dump/vent the excess air.

Whilst descending keep the valve closed and add just enough air to offset squeeze in the DS, then when you get to your target depth open the auto dump to the point where you see air just starting to bubble out, then close it back a little. The valve is now set and when you start to ascend, or raise your arm the valve will automatically vent air to keep your buoyancy the same.

Unless you change depths repeatedly during the dive and keep going up and going down this is the most efficient way to use the valve and really requires little or no input from you during the dive or on ascent and uses very little of your air to manage it.

If you want to dive the DS as insulation AND buoyancy then you do have to be very careful, it is easy to put too much air on the suit and end up inverted or pop your fins off if the air goes to your feet, so you really need to have your required weight dialled in correctly. I don't dive this way but if you do then I am sure someone else can advise you how best to mange the suit.

Best wishes and good luck with open water - Phil.

 

[jamesadele]

Thanks for all the answers guys they are very much appreciated. However some of the advise we cant really follow because the question of if or not to use the DS as buoyancy is not ours. Our instructor wants us to learn using the DS for buoyancy control and we are only allowed to use the BCD at the surface. In the pool we used the BCD for everything because we had no dry suit. No one in the group really seems to have much of a problem with the Shell dry suits in terms of buoyancy but like I say the wife has had to borrow one of the instructors suits because none of the rent-able suits fit and its totally different being the neoprene type with this auto dump valve.

I think from all the great answers you have given we should be able to get the hang of it but we don't get much chance to experiment with it due to having all the skills to run through, which is why I wanted to clarify how this valve thing works so that i maybe able to understand whats going wrong and help her out.

Thanks again everyone for the replies.

 

[TSandM]

Each click of the valve increases the pressure that's required to open the valve spontaneously. So, the more you click it down, the harder it is to vent.

If your suit is venting spontaneously when you don't want it to, there are a couple of possibilities. One is that you are overweighted, and having to put too much air in the suit to get neutral (this is assuming you are using the suit for buoyancy control, as most new divers are taught). Beyond a certain point, it becomes difficult to maintain the air in the suit, because almost any motion you make will allow air to reach the valve and vent. The solution to this is reducing the overweighting. It should not be difficult to keep the amount of air necessary to equalize up to 100 cf of air in the suit. For larger tanks, it may be necessary to put some of the air into your BC, as well.

The second reason for spontaneous venting is poor trim. Trim is more important to the dry suit diver than the wetsuit diver, because diving in a head-up position allows air to accumulate around the shoulders and escape from the suit. Even a properly weighted diver will lose suit gas if sufficiently upright. The solution to this is correcting the trim problem, which may involve posture or may involve moving some weight around to allow the diver to balance.

I personally think that closing down the dry suit valve is a risky behavior, because if you get distracted or stressed and end up going up in the water column much at all, you may reach the point at which the gas has expanded sufficiently that the suit can no longer vent it to neutral, and an unplanned ascent is now unavoidable. I dive with my valve open all the way until the valve begins to leak. At that point, clicking it down one or two clicks will often stop the water trickle, but still permit quite easy venting. I never close my valve unless I'm forced to spend sufficient time at the surface that I want to blow the suit up for insulation.

 

[JohnN]

Thanks for all the answers guys they are very much appreciated. However some of the [-]advise[/-] advice we cant really follow because the question of if or not to use the DS as buoyancy is not ours. Our instructor wants us to learn using the DS for buoyancy control and we are only allowed . . . .

As the other posters have said, using the DS for buoyancy is not "right" or "wrong", but an competent instructor should recognize this and accommodate their students if one technique isn't working. I see you're from the UK, is this a BSAC thing, or just instructor rigidity?

If your instructor won't entertain a different technique, I'd suggest looking for someone else, I find using the BC for control the easiest.