Need Some Advice - RE: USD AquaMaster DA Air Leak

[Terry]

Recently I noticed a tiny air leak from my USD AquaMaster DA when my tank pressure gets low; usually somewhere between 500 - 1000 psi. I suspect the problem to be with the 2nd stage caused by the adjustment of the IP at 110 psi. I remember seeing or hearing from a source that the tank pressure played an important roll in regards to this when you set the regs IP. If I remember correctly; when I adjusted this regs IP I did it with a tank pressure of 2200 psi. Any advice or suggestions that any of you might have regarding this matter would be greatly appreciated. Other than this problem the reg breathes great, and I'm wondering if using a different tank pressure when making this adjustment would help to correct the problem. If not; then I guess it's time to give the second stage a close inspection. Happy Fourth To All, and Safe Diving To You! Terry Stevens AKA VintageDiver

[Captain]

Put it on a tank with 300 to 500 psi and increase the IP until the second stage begins to leak. Back it off until the leak stops than just a hair more. IP should end up between 135 to 145 psi when you are finished.

Tom

[Terry]

Tom: Thanks for the info. I'll be sure to put the next to near empty tank to good use. Is this the way that you set your IP, and if so have you ever had any problems? Hope you had an enjoyable 4th! Thanks again, and Safe Diving To You. Terry

[Captain]

Yes, that is how I do. Never had problems.

Tom

[SeaRat]

If you put the DA Aquamaster on a tank at 300 psi, and it doesn't leak but it does in the water, you may have another problem. If it is adjusted to it's finest and bigins leaking at about 500 psi, and leaks on land, then the problem is in the first stage adjustment. If however, it does not leak on dry land, it may be the duckbill valve's adjustment. One of our other posters here described problems with duckbill valves, and here is what I said to him in a PM:

I agree with you about the duck bill valve being a royal pain. There are several problems, and I'll give you a bit of history on this. The duck bill valve originally had it's own housing, and so was shorter. It fit onto a projection within the bottom box, that screwed onto the bottom box. This is how my DX regulator works, and is the same way that the older DA Aqualung regulator worked.

The duck valve uniquely handles the problem Cousteau originally had with balancing the valve to the water pressure. It provides a flat surface that fits exactly against the diaphragm of the regulator. This makes it subject to exactly the same pressure as the diaphragm. The original way of mounting it from the inside of the box. through a part that unscrewed from the box, was without doubt the best way of doing it. But it was also expensive. So they built the bottom box into one piece, and used the duckbill to go inside and then over and outside the exhaust tube.

This change cut production costs way down, but also compromised the valve. The valve needed to be changed much more often, and it was made thinner than the original valve (I still have one, which I recently took a photo of too). Because the valve was bent over the tube, and because it was always in contact with the hose and could never really be rinsed well without disassembly, the valve deteriorated very quickly.

Today, there is another problem with the duckbill valve--it is made too short. The ones from the 1970s were longer, and this gave more room to bend them over the tube. The ones I recently picked up from Vintage Scuba Supply were of very good quality, but too short really for the USD bottom box. The reason is that they need to be down below the midpoint of the diaphragm so as to not leak air when verticle in the water. If they aren't (and they aren't in the shorter form), if the regulator is well-tuned to about 1.5 cm water pressure or less, then they will leak because their openings are higher in the water column than that. A de-tuned regulator which draws about 3-4 cm water pressure has no problem with the current valves, as this is the suction effort needed. These valves do work wonderfully on the Trieste II, however, as it has a smaller housing; the same would probably be true of the plastic Voit 50 Fathom and the Jet Air (USD plastic regulator), as they had a different, smaller opening and shorter route to the middle of the diaphragm.

To make a long story short, I've found a way around this, and that is to use the USD bottom box off a DA Aqualung regulator on my DA Aquamaster or Mistral. It's a much better design.

Concerning the mushroom valve on the Snark III, my Snark III leaks in certain positions because I have it well-tuned, and the valve diameter is quite large. This means that, in an upright position, the opening on the mushroom valve is >1.5 cm above the center of the diaphragm, and the valve opens and air leaks through. This is due to the water pressure itself.

I have an AMF Swimaster MR-12 regulator, and just received the poppet housing for the second stage. Now all I need is the seat, and I'm in business with it. It will become the octopus for my Trieste II.

I will try to get some photos loaded onto this page to illustrate it the problem. It is possible to pull the newer duckbills into the case far enough not to be the problem, but it is more difficult than it was in the 1970s due to size differences. But the new valves are of much higher quality, and will last considerable longer than the older ones.

John

[Terry]

Thanks John! Now that's an interesting concept; the flutter valve (duckbill). I never even gave that a thought; but it made a lot of sense when I read your post and gave it some thought. I don't believe the problem is in my 1st stage, and was more inclined to believe the leak was in the 2nd stage until I read your post. You and Tom both have given me some good pointers on where to check and how to correct the problem. Thanks, and Safe Diving To You! Terry

[SeaRat]

Several of you have PMed me about the new duckbills. While they are somewhat shorter than the originals that I have, there are two things I did that made the problem worse. Before I tell you of those, let me explain something.

I have had experience with a DA Aquamaster leak myself, and those photos came right after a "leaky" DA Aquamaster dive. As a matter of fact, the water seen inside the reg in the photo was river water from the Clackamas River. I had discontinued using the regulator, and switched to my backup single hose after turning off the DA Aquamaster. The water came because I was short on non-return valves, and had not used one in the intake hose side for this dive.

The photo with the duckbill valve in the case was as it was after that dive. You can see how short it is in the photo. I like to preserve my duckbills with silicone grease. I also use some 1980s hoses which are impervious to deterioration. These hoses were made out of a different compound, which was thicker than the originals and less stretchy. Therefore, when I mounted the hose onto the box with the duckbill in place, it pulled the duckbill valve up into the hose housing. This can clearly be seen in the photo. You can also see the two edges defined, and see how it was pulled up.

To keep this from happening, it probably would be good not to use silicone grease on the valves, but use talic instead. Also, if you use newer hoses that do not easily fit over the opening, then pull the duckbill down into the case so it has some travel distance. The newer valves don't have quite so much room to play with as the older ones. If your regulator is finely tuned, and the valve becomes pulled up like this, it could lead to the leaks I've discussed here.

One final point. This series of posts is a compilation of information I've been developing over the last month or so. The quoted text was written about three weeks before the post above, and you can see that I modified my stance in the post from the letter a bit. I do it here too as I develop more information, and pass it along to you. There is no right or wrong here, just a discussion of a problem and possible solutions.

John

[TENNESSEE DIVER]

SEARAT, DO YOU HAVE ANY MORE OF THAT NAVY EXPERIENCE YOU CAN SHARE WITH US LAND LUBBERS, THAT WOULD HELP ON OUR OLD TWO HOSE REGS?
I WANT TO SAY THANKS FOR ALL THE PREVIOUS ADVICE AND HELP FROM YOUR POST ON THESE PAGES.
I HAVE REPAIRED USD REGS FOR OVER 40 YEARS BY THE MANUAL, BUT LEARNED NEW WAYS TO SET UP FROM YOUR POSTS THAT IS FAR BETTER, THAT MAKES FOR EAISER BREATHING.
WISH I HAD KNOWN THAT BACK WHEN, IT MAKES ONE HECK OF A DIFFERENCE. FAR BETTER THAT THE FACTORY SET UP.
THANKS FOR THE LATEST POST, I,LIKE OTHERS, HAVE FOUGHT THIS PROBLEM, BUT NEVER GAVE THE DUCKBILL A THOUGHT, JUST LUCKED UP AT SOME POINT AND GOT IT CLOSE, I GUESS.
SO GOES TO SHOW OLD TIMERS DON'T KNOW EVERTHING, THERE IS ALWAYS ANOTHER WAY TO DO IT ---KEEP IT COMING---- RON MILLER

[Terry]

Hi Ron:
I'm in complete agreement with your comments. The advice and helpful comments that have been offered on this board are very much appreciated by I'm sure many. Thanks Guy's, and Safe Diving To You! Terry

[ScoobieDoo]

"To make a long story short, I've found a way around this, and that is to use the USD bottom box off a DA Aqualung regulator on my DA Aquamaster or Mistr

SeaRat, I'm confused - it thought all DA's were mfg by Aqua Lung and are Aqua Masters.

[Terry]

John & Tom;
Now that I got "Mr. Procrastination" to take a hike I finally got around to making adjustments on that USD AquaMaster reg. Those pictures really came in handy John; THANKS! I printed out this thread along with the pics and examined them while I was looking at the inside of my reg. I see what you mean regarding the exhaust valve not crossing the midway point. I did as you suggested, and also put a nice single wrap of black plastic tape around the outside of the exhaust valve where it folds over the inlet tube. This along with some corn starch kept the exhaust valve in place when I re-attached the exhaust hose. Then I went and got that tank I used on a dive the other day which was down to 500 psi and reset the IP as you suggested Tom. Right now I'm at about 130 psi. Now all I've got to do is find some time to take this reg out for a test dive. I was very pleased with the way this reg breathed already, and hopefully these adjustments will correct that very minor leak that I was getting at low tank pressures. Thanks again to all of you who posted any ideas on how to correct this problem, and Safe Diving To You! Terry Stevens AKA: VintageDiver

[Terry]

Problem Solved! I managed to get the AquaMaster out for a trial dive today; had her down to 40 feet and no problems. That very minor leak I had has been cured, and obviously it was one of the problems that was mentioned by Tom or John. I followed both of the suggestions that you guys offered and problem solved. Thanks guys! Safe Diving To You! Terry