Doing a pressure test with vacuum before our tank test and getting a drop from 10 to 8 in. Hg in about 10 mins.
From the guide it should be only about 9 in 15 mins.
How critical is the vacuum test in terms of the drop?
Check all the penatrators and bolts and all seem fine. Only thing we haven’t touched are the front end caps of the main & battery enclosures, they are as fitted from BR. Should we pull those and redo the silicone? Any other main items to recheck or comments?
Second test from 13 to 10 in Hg over 15 mins.
Have you tested and confirmed your vacuum pump isn’t leaking? I’ve bought 3 different vacuum pumps and all 3 leaked. Rusty and others, on the other hand, haven’t had any problems with their pumps. Guess I’m lucky. 
Yes I thought it could be that too so tested it with the plug and it held solid.
I just tested the battery enclosure by itself and it is holding with no drop at all after 10 mins so at least looks like narrowed it down to main enclosure.
Might have used too much silicone on end plate maybe…
Well having no luck pressure testing. Rechecked and redid all the main enclosure seals front and back. Still about the same loss as I started with. All the penetrators are tight.
I guess next step is remove all the penatrators completely and start over 
@schoonerlabs - I would start with the tether penetrator. Remove that one and replace it with a blank penetrator or plug and then test again. The tether is the only place the air can leak through if the vehicle is properly sealed. Basically, a small trickle of air can get pulled through the entire lengths of tether cable and into the enclosure. This normally happens very slowly, but maybe it’s happening fast enough to change the results.
Give that a shot first and see how it goes. Hopefully we can get it working better before it goes in the water!
-Rusty
Thanks again, that was our next thought as well.
Just as a thought, it might be good to add a step during the build to pressure test the penetrators with the enclosure prior to wiring them in place, since pilling the electronics tray in and out can be a handful if doing multiple times.
@schoonerlabs - Good idea. I’ll propose that over here and hopefully get it added to the instructions.
Tested again with tether removed and replaced with a plug and get about 1.5 drop now over 15 mins, that is with both enclosures connected to vacuum.
So still seems to be a bit of a leak somewhere but may tank test it as is for now since wont be more than 8 feet deep.
Next I guess is pull all the penetrators and redo them.
@schoonerlabs - If I were you I would probably test it in the water just check it carefully at first. It definitely won’t be a fast leak if there is a leak.
-Rusty
That was my thinking as well. See if it leaks and go from there. We have a fresh water indoor test tank so easy to monitor.