Vacuum systems, do you still do a camera-free dunk?

Hey all, 

I have an Ikelite 200DL with their vacuum system, and I've really liked it so far. That said, one thing irks me about setup. They recommend that you do a test in a dunk tank without the camera housing to check for leaks, then take the back door off again to put the camera in, before doing another test with the camera in it. My problem is that after the no-camera dunk test I always end up with a wet main o-ring and have to completely redo the rear seal. It feels like I'm just introducing more risk this way vs if I just did a careful, dry, initial setup with the camera installed, then pulled a vacuum and checked it the next morning. I always give the housing overnight to detect any loss of the internal vacuum. 

So, if you are using a vacuum system and leaving the housing overnight, do you really need to do that extra dunk with an empty housing? What is your setup routine with your vacuum system? 

Thanks, 

Austin 

Hi Austin

Interesting question. If I’m travelling on a dive holiday I have to remove my 45 degree viewfinder to get the housing in my Pelican case.
 

On arrival I refit it, set up the housing with a port, vacuum seal it and then take it for the first dive without a camera. Assuming all’s well, the camera goes in for dive two, reseal and away we go. No dunk test 

That’s the only time and reason I’d do a dunk test or cameraless dive - unless maybe I had concerns about something and wanted to check without a camera. I rely on the vacuum system and leak detector to alert me to problems.  
 

If you’ve got the vacuum system confirming the seal, and it’s working correctly, I’m not sure a dunk tests adds much. 
 

I just bought a used NA-16 housing to use as my scooter cam. I have a leak detector (V4) on my other housing (different housing, different camera). I transferred it to the new housing and pulled a vacuum on the empty housing. Left it for 24 hours... no issues. After that I just dove the housing using the leak detector. I did verify the moisture sensor worked (needed a new battery).

Before the leak detector, I would always test a new housing by dunking it empty in a long tube I have that is 'deeper' than my rinse bucket, with paper towel in to check. Also after any housing change (port swap, whatever). Now with the leak detector, if I'm concerned I'll put it on the night before. If nothing has changed, I'll just run the vacuum and dive it.

anytime you disturb the o-ring you risk issues such as a stray hair on it or water inside the housing.  The whole point of the vacuum system is to confirm you have no problems.  I am meticulous with my o-ring cleaning and prep and then rely on the vacuum system to confirm I have not missed something.  I have never done an empty housing test with my system and cannot see any reason why I would.  Doing the dunk test takes you back to square one as you have disturbed the o-rings.

I do it once when I get the housing to check it out, and that's it. Really, with a vacuum leak detector, you don't really need to do that.

If I'm on a typical dive trip, I'll prep the camera rig the night before and let the vacuum system tell me if i have a leak in the morning.   No need to put it underwater for this test.  (And I've seen problems surface with the test.)

During the day, I'll typically crack the case at lunch time to swap camera battery, sometimes to download images as well, or change lenses.  Get the rig prepped again before lunch and pumped back down so it has an hour or so to surface any new leaks.  Meanwhile I'll typically be charging 8 AA's, a focus light battery and a camera battery to swap back in after the afternoon's dive.  (For me, typical is two dives in the morning, a lunch break and one afternoon dive.)

I'll typically not crack the case open while on the boat unless I need to fix some issue I missed.  The camera battery lasts more than a day, even when I was shooting a D810 and using the pop-up flash a lot to trigger my strobes.  My D850 doesn't have that, so the battery lasts even longer.   Still, I typically change it at noon on general principles. 

What Sting Ray and Great White say about lead vacuum testing is clear and correct.

The only times I do a camera free dunk is after I have been working on the housing, such as replacing small O-rings or similar, and the housing shows a leak during a vacuum test. Otherwise I do not bother with a dunk test. 

For daily diving, after I have installed the camera in the housing and sealed it, I do a vacuum test and check the green LED flasher every half hour or so for a couple of hours, or overnight.  If the vacuum holds for two or more hours, the housing with camera is ready to dive, it tells me a water dunk test is redundant.

Let us compare the Water Tank vs the Vacuum test.
 The water tank test uses the atmospheric pressure plus the small water pressure (depth of water in the test tank) to try and force water into the housing. The test is simple, and if no bubbles arise, usually takes a minute or so.

 The vacuum test uses specialized electronics to test the difference between the atmospheric pressure and the negative (vacuum) pressure inside the housing.  The test is dry and if the vacuum holds for a few minutes to overnight, one can go diving without further ado.

 In practice, the vacuum test is more useful than the tank dunk, as it  continues to monitor the housing leak status during the dive with its re-assuring green blinking LED.

Great information and feedback. I have been using the Nauticam housing for my camera for three years without incident, without dunk tests and I love it.  I have relied on the vacuum system and have yet to have any performance issues. I love the vacuum systems, it has proven to be highly reliable in experience.

I also have a Nauticam housing with vacuum system/leak detector.   Never have felt the need to test with a dunk test.  Highly reliable system.  Wish I could say the same for my strobes