USD J-valve Manifold Creep, is it normal?

[leicamshooter]

I wanted to thank all of you for all the help in setting up my twins. Bryan was so helpful in restoring my DW Mistral. The Alan Kauda harness, with Rick Green bands is so nice I feel. Alan was also good enough to provide the J-valve rod you see in the picture.

I have a question regarding my J-Valve on my USD solid bar manifold.

I filled my doubles to about 750 PSI as specified in the USD manual. I remove them from the fill station, then attach a balanced diaphram single hose reg with a SPG and 2nd stage.

I return the reserve handwheel to the "start Dive" (UP) position.

Fully open cylinder valve.

then gradually reduce cylinder pressure, watching my Scan 4 USD digital SPG. When I get to about 450 PSI I hear a slight hiss sound coming from within the j_valve assembly.

It is not an external leak, as I tested with soapy water and saw no bubbles.

It looks to be the tank in the J-valve side trying to fill the other tank. The tank that at this point I must be breathing down correct?

There was no hiss until I reduced pressure to about 450 PSI.

I breathe it down to 80 PSI, the hiss is slightly louder. I breathe it down to 0 PSI with obvious breathing resistance. I listen and the internal hiss continues.

I actuate the reserve lever into Down position. The tanks make a equalizing sound. SPG reads 260 PSI. There is no hiss anymore.

My question is whether this hiss is normal or is my j-valve not functioning correctly. I took it apart and everything is as it should be with good O-rings backup rings etc. It should be as it is a New never before used manifold I found. Please advise

[captain]

No J valve is a complete shutoff at the designated pressure and if given enough time may eventually equalize the two cylinders. What you observed is pretty normal. When you get to between 400 and 500 psi the J valve will begin restricting air from the left cylinder and depending how well it holds back pressure and how hard you are breathing you may or may not feel breathing getting harder. The best test is to breath it down to where you notice the increased inhalation resistance and note the pressure it occurs at.
You may reach a pressure where the J valve will no longer allow air to flow from the left cylinder to the right but that could be as low as 100 psi or less.

[leicamshooter]

That's what I was hoping... The resistance was quite noticible when I got down to 10PSI. however, I was expecting my SPG to jump around more when the valve was in dive Up mode. I've read in other posts that this occurs sometimes. Maybe this is a lot less of an issue with doubles. Also, the Scan 4 is probably only taking readings every 5 seconds as oppose to a traditional gauge.