Water in BC

[crpntr133]

I would have to disagree with part of your post pasley. I don't agree that a dump valve causes more water to enter the BC. I use nothing but my dump valves and very rarely do I have water in my wing. When I do have water in it, it is maybe a mouth full.

To add to the cleaning process, put a cap full of Listerine, or other mouth wash, in the wing and rinse with water.

 

[pasley]

I would have to disagree with part of your post pasley. I don't agree that a dump valve causes more water to enter the BC. I use nothing but my dump valves and very rarely do I have water in my wing. ....

Ok thats fine. Your experience and gear configuratioin (Jacket BC Vs Wing) is different than mine. My comments are based on the comments of others on this board, my own experience and some logic and some experimentation.

My logic: The purge button on the end of the hose presents a small opening of approximately 0.5cm (1/4 inch) if you look inside the purge valve opening at the actual valve opening. The dump valves on the other hand are 5.0cm (2 inches). So I would argue that an air bubble coming out of the purge button opening has a better chance of blocking most of the water and of admitting very little. The dump valve on the other hand will emit a larger bubble and also admit more water. If the BC is in fact empty or nearly so, or positioned so that the valve being operated is not the highest point of the BC causing the air bubble to be trapped and not reach the dump valve you are operating, then as it is a larger opening it should logically admit much more water than the purge valve would. In this case 8 times as much per second of operation.

My experiment: I had never thought about the amount of water in my BC and Purge Vs Dump Valve until a few months ago when this question first was raised by another diver on this board. I then paid attention to the amount of water in the BC following a dive. I also experimented and on some dives used the purge button on the end of the hose only and not the dump valve. On other dives I used the dump valve part or the purge valve located on the inflator hose you activate by pulling on the hose. I noticed a difference between the two with the dump valves admitting noticeably more water than the purge valve did. I have quite using the dump valve for the past 20 or so dives this year and have noticed a reduction in the amount of water in the BC. Your experience may be different as you may rarely open your dump valves, or do so only when there is more air present and not when there is no air present. Newer divers tend to compensate for waiving everything around (hands, arms, fins etc) which creates lift by dumping air long after their BC is completely empty, or while not having the dump valve they are operating as the highest point on the BC, thus trapping air.

So that was my thought process (logic) and my experiment. Now I will admit it is not scientific and I did not measure the water in the BC, just the apparent quantity after a dive, which could be deceiving. Ok so there you have it. Why don't you come out to Southern California and dive our kelp forrest with me. We will do several dives. On each dive one of us will use purge valve only and the other only dump valves and then on the next dive we will switch. We will empty our BCs into measuring cups and compare the results of our dive over say 4-10 dives (2-4 days of good beach diving). How is that for a scientific experiment? Malibu to Laguna Beach and diving, how can we go wrong?

 

[crpntr133]

Don't get me wrong pasley, I didn't say that you were wrong I just said that I would disagree. I'm not here to agrue the point, I just didn't want anyone that read this thread to think that a dump valve is the spawn of Satan. Kinda like the back inflator will dump you on your face every time...not mine. It may happen to others but not me. I am not saying that I am a better diver it may be conditions and sometime this may happen to me.

As for the diving together, it may be a while but I will take you up on that.

 

[pasley]

Crpntr133

I understand what you are saying and agree that there is nothing wrong with using the back dump valves. They are just different sizes and designs and so have different characteristics. The larger dump valve will vent air faster (hence the name dump) than the purge valve, and as a result potentially admit more water. But that hurts nothing. I choose to use my purge valve as my primary venting orifice of choice most of the time. That is a personal choice. If I have a bubble I can’t get out or don’t want to shift my position to bring the bubble around to the purge valve shoulder, I will use the dump valve that is closest to the surface depending upon my orientation at the time. I was not intending to argue either but only to say that if water in the BC is a concern to the diver, then they should try to use the dump valve less and the purge valve more. With experience it will no longer be an issue either way as they will not be holding the valve open as much once the air is out.

As for back inflate BC, if properly used they are great and if I ever buy another BC will probably be what I purchase. An error some make is trying to inflate them on the surface so full they are as hard as and air mattress. When they do that the BC will tend to ride up and in turn push then forward a bit. Solution, use the BC as intended as a Buoyancy Control device and not a life jacket/raft and as long as your head is above water you are fine and leave it at that.

Now about diving, I plan on being around for many years so when ever you are in the neighborhood.

 

[String]

Back lower dump valve is the one i probably use 90% of the time, means i can swim around horizontally without having to shift position to dump air. After that the rear right shoulder dump is used if im slightly head up at the time. Using the hose for me is very rare, maybe once a dive if that.

 

[Geezer]

On the other hand - I rarely use the back dump valves, and use the hose almost exclusively.

Why? With the back dump valves, I can't tell when they stop releasing air, and start allowing water in. With the hose, I can watch the air exhaust, and end the process at the right point. No need to go vertical to use the hose, either - just roll to the right, and the hose rotates to the highest point for the air to flow. I've noticed a significant reduction in accumulated water, and more positive control - YMMV.

 

[String]

The only time i get more than 1/2 a small glass of water in my BC is when i try to empty the BC when its already empty. This happens on ascent as i gradually switch from BC to buoyancy to 100% drysuit at stop depth for warmth (on reaching 6m i want all the air in my suit and none in the BC). That final purge to make sure its empty will inevitably get water into the jacket. Its not a huge amount or a big problem though.
The back valves i tend to have no issue as i can hear and feel air coming out of them and rarely if ever pull them long enough to dump all air. After a while you just get used to knowing how long to dump to stop a rise and so on. Rolling to use a hose is too much effort for me