A little help troubleshooting SI-Tech dump valve

(I searched here and Googled, no leads, so sorry for asking...)

After fooling around with a neck bio seal and other dead ends, I figure it must be the shoulder dump valve that's turning my drysuit into a dampsuit. (SI-Tech high profile, about 4 years old.)

I've taken the thing apart and it seems to be clean and working fine. I've pressurized the suit and checked every seal and valve, no problems--but that doesn't reproduce conditions at depth, where the outside pressure would be much greater. (suit squeeze as I descend, say.)

It's also possible that there is a leak around the valve. The rubber seal on the suit looks fine though, as does the little white disc which sits on the inside of the assembly. Perhaps the assembly is over-tightened? (I can't find a manual online.)

I'm almost out of ideas... What should I try next?

Remember that, although outside pressure is higher at depth, so is INSIDE pressure. The air you put in the drysuit is at ambient for whatever depth you're at, so the gradient across the valve is never actually very high.

If you can pressurize the suit and have it hold pressure overnight, the overwhelmingly likely culprit is your neck seal.

Are you sure it's actually leaking and not just condesation and perspiration?

If it's leaking, as in real sea water with cold spots and all, test the suit for leaks by turning it inside out and filling it up with water after clamping off the wrist and neck seals. Do this in your driveway or somewhere similar where a few gallons of spilled water won't matter.


Dan

Sometimes the outside pressure will be a bit greater, if I let the suit squeeze, but it's never too much I guess. I shouldn't have said "much greater." (I can't positively remember squeeze being tied to the leak anyway.)

Dan, it's definitely a leak. I haven't tried filling it with water to check for leaks, just air... and I didn't leave it pressurized overnight at that like Lynne suggested.

I thought it was the neck too--it still could be but I am suspicious and here's why. My last dive, I used a "bio seal," and it did seem to help the neck seal well. I had a leak, but I felt the cold water at my left shoulder, and not running down my neck. (I have definitely experienced a neck leak before from a poor fold or moving my head too much and this may be a contributor to the problem.)

Can you guys confirm the valve assembly? Perhaps I am missing a part that I don't know about.
On my dive tomorrow I'm going to get my buddy's help looking for bubbles while I wiggle around and try to reproduce the problem. I'm always concentrating on the dive like a good buddy instead of my wet shoulder so I end up troubleshooting based on poor memories.

Thanks for the ideas... I realized I even posted about this back in April! I got complacent.

What suit do you have? The fill-with-water leak test method is a good one. Another one I use is to jump in a pool with just some regular cotton clothes on under the drysuit and hang out for a minute. I jump out and pull the suit off, and any leaks are apparent by the wet spot on my clothes.

You can tighten the valve attachment nut pretty good but not more than hand tight. Use some silicone sealant between the valve and the suit on the outside. If you have a DUI suit with the overlay on top, make sure you put silicone between the layers of fabric around the valve hole.

Matt, if you want to do the cotton clothes leak test, you're welcome to do it in our pool.

The suit is a Bare CD4. (compressed neoprene) Do you mean sealant, like tub & tile goop? I like this plan.

Thanks Lynne, I will let you know if I need it!

The sealant you want to use is the 100% silicone sealant, sometimes called Aquarium sealant:


You will want to unscrew the nut on the inside of the suit, remove the valve, clean all the existing sealant off the valve and suit that you can, apply some sealant to the face of the valve and replace the valve and nut. Do not put so much on that when you put the valve back on that it oozes everywhere.

FWIW, my experience with loose neck seal leaks is that it is very apparent. Upon turning my head to the side I will get a cold blast of water down my neck.

Thanks. I may have some aquarium sealant around around, I've used it before. To the garage...

Well, my experience with a leaking neck seal wasn't that apparent. I think I have so much undergarment on that the water was running into the Thinsulate, and only becoming apparent when quite a bit had entered, and it got down to my belly and underwear.

There are days when I hate drysuits. And then I want to go diving again . . .