New Housing "Airlock" Vacuum from Backscatter

[John Bantin 101]

"Despite some proselytizing from some individuals, no vacuum system by itself can guarantee that a housing will not flood" - just like an oil-pressure gauge/light on your car does not guarantee your engine will not run out of oil, but if that light comes on, I'm going to do something about it!

Edited June 2, 2013 by John Bantin

[gdfallon 4]

Just returned from Bonaire where a fellow on the boat had the Backscatter system. According to him the vacuum caused a problem with his camera in that not all the buttons worked. His theory is that the vacuum caused the buttons in the camera to get sucked in a little bit which meant they did not meet up properly with the housing controls. Any comments on this?

[conger 0]

I just returned from Bonaire as well, we arrived home last night at midnight. We purchased two of the Backscatter systems, one for myself and one for my wife both worked great with no issues at all with any buttons, and we routinely pressurized to 10lbs. I am using a Seacam housing. I have the simple system without the lights, although our housings have audible and visible leak detection as a back up. I was away for 16 days and made 52 dives with the housing my wife made about 30 with hers. Changing lenses, downloading cards and restoring the vacuum was quick and easy. The only difference I noticed between my housing when it was under vacuum and prior trips was that I had to remember to release the vacuum to open the back or to change ports. I grew to appreciate that the Backscatter system requires you to insert the pressure gauge to release the vacuum, originally I though it would be nice to have a switch on the valve that is attached to the housing, but knowing that the default position has the valve sealed, and the valve is only open if the gauge is plugged in makes it almost impossible for me to make an error and depressurize the housing by accident. The system is easy to use and extremely light for travel. This system very quickly became second nature, and barely added any time to my camera rigging/derigging.

 

I was originally disappointed that I purchased the system from Backscatter without the lights before the one with the electronics was available. Now I am happy with the current system and I am not sure I would upgrade for the additional cost if I could do it again. Although I have not used a vacuum system for years I did have one with indicator lights installed on an RS in the 90's, I am much happier with the Backscatter system then I ever was with the RS. I can see the obvious advantage in general of indicator lights but for me it is not a big deal if they are missing. The ancient system in the RS probably is not comparable to more modern systems, but it did drive me crazy on my last dive of the day when I changed film and re-rigged the RS, I would then apply vacuum, and check after 30 minutes and have the green light. The next morning the light was red and I knew it was the temperature change, but I could either ignore the red light or repeat the pressure test. With the RS the pump was not mechanical it ran off the pressure fitting on your B.C. as I recall so it was really kind of a pain to pressurize. I think the biggest factor to consider with any system is how easy is it to use, from my experience if there is a choice between a hand pump and one that requires air or a/c or even batteries to run I would choose the hand pump. A hand pump reduces the chance that you will skip the vacuum just this once because of lack of an outlet, batteries etc.

 

This is not meant as a comparison to the other available pumps, this is a rare case where I did very little research before purchasing. It was an impulse buy based on an email Backscatter sent out before release of their product. It is also not meant to recommend going with a no light system over one with lights for anyone. For me I think this is the right choice, based on my prior experience but I think it depends upon the system, your rigging protocol, and your comfort level as well as any incremental cost. Finally I have no connection to Berkley White or Backscatter other then having made purchases from the Backscatter store in the past.

[JimDeck 2]

Just returned from Bonaire where a fellow on the boat had the Backscatter system. According to him the vacuum caused a problem with his camera in that not all the buttons worked. His theory is that the vacuum caused the buttons in the camera to get sucked in a little bit which meant they did not meet up properly with the housing controls. Any comments on this?

While anything is possible, it is highly unlikely that the vacuum would cause an issue with the buttons. At -5 inches of Hg (the recommended vacuum to pull) is only 2.5 PSI or the equivalent to about 5 feet in water. So it's as if you're diving the housing 5 feet deeper than your depth.

 

Jim

[drsteve 6]

" Changing the pressure inside of your housing at sea level using a pump is different than changing the pressure outside of your housing at depth using seawater."

 

Assuming that the inside of the housing is always at a lower pressure that the out side,

then only difference I can see is the size of the water molecule compared to an air mole.

 

And that is why commerical leak detectors use helium!

 

Acutally that is not why commerical leak detectors use Helium. Helium leak checkers are small mass spectrometers tuned to only detect Helium, which makes them equisitely sensitive. Since there is no Helium in the atmosphere there is no background signal except where the gas is intentionally introduced. With a small tube you can bleed Helium around each fitting and localize exactly which one is leaking.

 

On a related note, the Backscatter system looks great and the fact that it can easily be installed to existing housing makes it addtionally appealing. I am surprised that when I was at the Long Beach scuba show a few weeks ago they didn't display it prominantly at their booth. I probably would have come home with one. Years ago I ran across a videographer that had glued a Presta bicycle valve into his video housing and used a bicycle pump to pressrize his housing. He claimed that one benefit was that if the housing did spring a leak, you would see bubbles exiting the housing. It seemed a bit sketchy to me. I think vacuum pump systems are a much better idea.

[John Bantin 101]

When I first saw an SPG I thought it a good idea and got one - despite those who didn't have them telling me it could explode and kill me.

When I first saw an ABLJ (the original equivalent of a BC) I thought it a good idea and got one - despite those who didn't have them telling me it could send me hurtling to the surface with my lungs hanging out of my nose.

When I first saw a diving computer I thought it a good idea and got one - despite those who didn't have them telling me it could kill me and that I should use tables.

When I first saw a drysuit I thought it a good idea and got one - despite those who didn't have one telling me it could leave me inverted and drowned.

When I first saw a BC and thought it a good idea and I got one - despite those who didn't have them telling me BCs could leave an unconscious diver floating face-down at the surface.

 

Why do divers hate ideas that are obviously good? You will ALL be using vacuum leak tests (complete with flashing green lights) within a decade, apart from the dinosaurs among you!

Edited July 10, 2013 by John Bantin

[DocTock 6]

John - That posting is a classic! I would love to use it as my Signature!

 

 

I just added a Housing Sentry vacuum check with no electronics.

The vacuum added a level of comfort/ security; decreasing the level of risk of a catastrophe.

I used a hand pump as it has an attached gauge (and yes, everyone on the boat HAD to make a joke about the hand pump).

Prior to each dive I would check the state of the vacuum by simple insertion of the hand pump.

After checking the status, it became routine to re-plug the bulkhead, especially as the pin is chained to the bulkhead on a very short chain.

 

The biggest advantage for me is I ended up using my camera out of the housing more than I have in the past.

[newmediasoup 0]

Just returned from Bonaire where a fellow on the boat had the Backscatter system. According to him the vacuum caused a problem with his camera in that not all the buttons worked. His theory is that the vacuum caused the buttons in the camera to get sucked in a little bit which meant they did not meet up properly with the housing controls. Any comments on this?

 

I was actually on the boat the same day he was experiencing the sticky button on his housing. I won't get into which housing it was but I will tell you that in my assessment, the button that toggles between video and photo mode was getting stuck in the down position, causing the camera to be locked up. I experienced the same issue before with the same brand of housing last summer where I had pressed the "video/photo" button a little too hard and it would stay stuck in the down position. (In my situation last summer, we repaired this issue in the field by opening the hole in the delrin bracket of the button for the metal part of the button to have more breathing room. I didn't have any issues with the button for the rest of the trip.)

 

Regarding the guy at the Shootout who had a stuck button and thought it was related to the airlock, I told him to talk with the housing rep (who was on-site) at the Shootout to get the button swapped/repaired.

In my opinion the issue was not with the airlock but with the button on the housing itself.

[John Bantin 101]

John - That posting is a classic! I would love to use it as my Signature!

 

 

Please help yourself!

[Drew 0]

John, did you not hear? Climate change doesn't exist and the planet was flat once.... oh and it's only 6-9000 years old!

Why do divers hate ideas that are obviously good? You will ALL be using vacuum leak tests (complete with flashing green lights) within a decade, apart from the dinosaurs among you!

[roshanzamir 0]

very helpful.

 

thank you...

[aquanomad 1]

Im about to buy a leak check. Either the backscatter or sentinel. The sentinel looks more streamline is almost half the cost! Any reason to shell out double the money for the backscatter?

[NikonKidF3 2]

Im about to buy a leak check. Either the backscatter or sentinel. The sentinel looks more streamline is almost half the cost! Any reason to shell out double the money for the backscatter?

Just returned from another successful week of diving in Key Largo, using the Leak Sentinel on my Aquatica AD90. It adds a tremendous level of confidence and eliminates much of my anxiety when the camera hits the salt water.

 

I always assemble my rig in my hotel or condo before leaving for the boat, and don't have to open the enclosure to replace data cards or batteries between dives. I pump the enclosure down about 1/2 hour before leaving, and make sure the blinking green light is on before I leave for the boat.

 

Diving the Spiegel Grove, I did find that the light went from blinking green to alternating blinking red-green, the caution condition. I noticed this at about 90 feet. I didn't see any water in the port or the back window, and thought it very likely that the enclosure was being squeezed to a slightly smaller volume at 90 feet than at the surface, thus raising the internal pressure very slightly. This turned out to be the case, and upon ascending the line at the end of the dive, the light went to straight blinking green at about 60 feet. There was not a hint of water in the enclosure when I opened it up at the condo that afternoon. I have taken to pumping the enclosure a bit further down than before: 8-10 strokes on the pump instead of 4-6, and that seems to have taken care of the false alarms.

 

Ergonomically, the Leak Sentinel LED is positioned right at the top of the housing for me, in the second strobe bulkhead port, placing it at eye level every time I swing the enclosure up to shoot. I can't help but see the light and check that it is blinking green (it looks yellow underwater) throughout the dive. Battery life appears to be very long, certainly more than the 24 hours I spent underwater and leak checking my enclosure in the condo (I pump the enclosure down and leave it blinking overnight if I make any changes such as removing the port or replacing a bulkhead).

 

I think any vacuum leak detection system makes a huge difference in reducing anxiety about your equipment. The Leak Sentinel does the job for me with no fuss, no muss, no sticky mess. I think the other systems would do a fine job as well.

Willis

[diverdoug1 56]

Gates housing vacuum check system uses the same valve. Gates uses a battery powered pump. This system has been around for a long time for high end video housings. I have my own version for DSLR for over 8 years on request from customers. Not one had serious problems. No electronic is a plus. The pump with the gauge is all you need. It is only partial vacuum like -0.5 bars which simulates about 5m depth. User could either leave vacuum in or purge it. Very unusual to have a sudden o-ring seal failure when the housing is under equal hydrostatic pressure from the water column. Unless user decide to whack the port on a rock. I had over 8 years and more than 60 people with these vacuum valves for both DLSR or video housings. I know they work. Keep it simple. Electronic only adds more stress. The seal is checked on land and if seal is not working then the gauge will drop. Sort out the o-rings and then check again. O-ring either fail or working. They don't just decide to fail halfway. Anyway Backscatter version looks simple enough. Its the way to go for peace of mind.

 

Cheers

David

I put a hair across my main o-ring, and pumped down my system to 10" Hg. It took almost 10 minutes for the vacuum to fall below 5" Hg. So unless you make sure you pump down your system and check the pressure with the gauge at least 10 minutes later, AND before subsequent dives to make sure nothing got bumped out of place in the camera table, I still see a benefit for the electronic system.

Edited September 16, 2013 by diverdoug1

[ianmarsh 37]

I put a hair across my main o-ring, and pumped down my system to 10" Hg. It took almost 10 minutes for the vacuum to fall below 5" Hg. So unless you make sure you pump down your system and check the pressure with the gauge at least 10 minutes later, AND before subsequent dives to make sure nothing got bumped out of place in the camera table, I still see a benefit for the electronic system.

Doug,

 

Good point, indeed.

 

I have the non electronic version... seems like a solid piece of gear. Very reassuring, but: With that model, a STABLE vacuum reading is critical.

 

If the vacuum is changing, the housing is leaking.

If you start out at -10in/Hg and it "drops" to -5in/Hg the absolute value doesn't matter. It doesn't start to leak when it gets to 0in/Hg.

The ∆ indicates a leak, and if its leaking air, it is leaking water.

 

The point is, with a non monitored system, stability of the initial reading is key. Don't fool yourself into thinking a small change doesn't matter. It does.

 

However, be aware of temperature/pressure fluctuation.

 

ian

[pointy 4]

Why do divers hate ideas that are obviously good? You will ALL be using vacuum leak tests (complete with flashing green lights) within a decade, apart from the dinosaurs among you!

 

A leak check system is a good thing, but people are paying a lot for flashing lights to indicate either enough, or not enough vacuum. Such basic two point monitoring could fail to detect a slow leak, so we should hope to improve on that over the next decade.

 

An altimeter within the housing gives constant assurance that the housing is tight. Some Swiss Army knives come equipped with tiny altimeters, so maybe housing manufacturers will design better and cheaper vacuum monitoring.

 

John McCracken

[diverdoug1 56]

I plan on pumping my system down to -7''Hg, then if it goes from green to yellow in the time it takes me to get ready to dive, I will be alerted to a leak. I will keep in mind that a significant increase in internal housing temperature may give me a "false positive" leak test.

[Nicool 26]

Hi Folks,

 

I used to be more tempted by electronic vacuum checks, I mean the ones with a LED like Hugycheck, Leak Sentinel, Airlock electronic.

However I got troubling situations with my Leak Sentinel several times: the LED was green on land, and after a dive was no more (and it didn't return to green later). In another occasion I left the housing ready at home for a few hours, it was still green, and when arriving on the dive site, no more green. This did not sound logical to me so both times I did dive (closely watching the moisture alarm), and the housing didn't flood.

From above discussions it seems those "fake warnings" could be due to temperature changes. Maybe, but I am missing the purpose of feeling calmer when taking my gear underwater...

If I understood well the above talks, if I get a stable pressure after 30 minutes of vacuum, then it won't move no more, a leak would have been detected. Then I don't need any LED, right?

Actually there's one situation where I'm in doubt: what if your vaccuumed housing gets a shock, e.g. in the dive boat, let's say on your macro port. Any risk the vacuum between port and housing gets jeopardized? Then I'd see a clear interest for continuous feedback LED.

 

cheers

Nicolas

[John Bantin 101]

Sounds like you've got reliability issues with the electronics. The only time I got a false red on the Hugycheck (two different housings owned and a great many dive trips) was when I took it from a cold environment where I closed up the housing into a very warm pool. I wouldn't countenance a housing without it now. (Nauticam's will be available any day now)

 

I've had two red lights, both with the D800.

1/ I arrived in Cyprus and put my housing/camera together for an early morning start, in my hotel room. I went for dinner with green flashing. When I came back I had a red. Reassembled the camera and woke up in the night to see a comforting green light.

 

2/ Went to Malpelo. I assembled the housing/camera during a rough crossing. Went for dinner. Came back to find a red light.

 

That's twice I might have lost a D800 and lens. It's very comforting to see the green light reflected on a cabin ceiling and helps you get a good night's rest!

Edited September 20, 2013 by John Bantin

[diverdoug1 56]

Going from a 71 degree airconditioned room to 85 degree water caused my vacuum reading to go from -10"Hg to -7"Hg. If it had caused a slightly greater decrease in vacuum, my indicator light would have flashed yellow.

Edited September 20, 2013 by diverdoug1

[markdrayton 12]

I have just come back from the Red Sea with my bulkhead Housing Sentry equipped housing. I strongly support the reassurance that the flashing green light provides although of course this is no substitute for careful assembly procedures. After one rather rushed equipment change in my hot and dark resort room, the housing was de-pressurised but it seemed to take longer than usual to reach the green light pressure. As I put the housing into it's carry bag a few minutes later, the flashing changed to red. Reassembly of all the o rings traced the probable leak to salt crystals on the main housing o ring/seating, with no subsequent problems on re-cleaning and reassembly. I believe that in all probability, Housing Sentry saved an expensive flood and a disappointing photography trip. No matter what we all believe about our own careful and methodological procedures, we are all susceptible to human error, especially when under pressure or in suboptimal conditions.

 

A quick plug for Housing Sentry - I discovered that the electronic module was not functioning properly during preparations shortly before this trip. An exchange of emails between myself, Bill and Mary at Underwater Camera Stuff led to the electronics speeding back across the Atlantic, being repaired (threshold components replaced), exhaustively tested and express couriered back to the UK FOC, all in 8 days door to door. Remarkable service and back-up for their kit.

 

Mark

[John Bantin 101]

Some day all housings will be equipped this way....

[drsteve 6]

I don't want to be a shill for Backscatter, but I bought one of their systems and am very happy with it. It was a bit pricey but the peace of mind is worth it. Besides no one is suggesting that a vacuum system is a substitute for regular maintenance and careful inspection during assembly. Being able to measure the housing integrity sure beats looking for bubbles in the rinse tank.

 

It also solves one of the things that has bugged me about my housing for years. That is that the main housing o-ring is intentionally under compressed by design. If you go to any o-ring catalog or consult the Machinist's handbook, there are very clear design guidelines that date back nearly a century. Face seal o-rings are supposed to be clamped tightly enough that the two metal surfaces come into contact, with the o-ring trapped in the groove. Every housing I have seen violates this design rule. I believe that it is because the clamping force required for such a large o-ring would require bolts, and housing vendors perceive that this would be too annoying. Instead, for convenience, they use suitcase style cam-latches, which cannot provide enough force to complete the face seal. That is one of the reasons there are so many floods in the rinse tank. An under-compressed o-ring seal can flood when bumped. Most housing vendors explain away this design decision by saying that the water pressure causes the housing to "seal better" when you take it diving. This is certainly true, but it is really an acknowledgment that the seal is marginal at the surface! Perhaps someone can correct me, but I think that only Hugyfot uses bolts instead of suitcase clamps.

 

Another benefit from a real face seal, is that if you shore dive with your housing (which I rarely do), the gap between the two surfaces can allow sand to enter. It doesn't necessarily compromise the seal, because it is outside the o-ring, but as you descend, it gets ground into the surface as they are pressed together under pressure.

 

The vacuum check system solves this problem. The partial vacuum provides the additional pressure to complete the face seal. It also locks the ports. I love it!

[ChrigelKarrer 52]

Perhaps someone can correct me, but I think that only Hugyfot uses bolts instead of suitcase clamps.

 

Yes, Hugyfot uses bolts to tighten with a allen wrench.

I am not sure if this closes the housing better nut i am sure that this avoid a semi-closed / unlocked latch snapping open under water.

Chris

[John Bantin 101]

http://www.undercurrent.org/UCnow/dive_magazine/2013/LeakTests201304.html