I chose my latest housings simply because of one unique feature. The Hugyfot comes with an electronic vacuum leak test system that allows for non-destructive testing to see if it’s sealed properly. No more gingerly lowering a housed camera into the rinse tank to see if I can spot any bubbles escaping, and wrenching it out before the camera is toast.
Those professional film-makers who use their expensive video cameras in Gates housings can opt for an equally expensive Gates vacuum leak test system that uses a mechanical pump with a pressure gauge attached.
They pump the housing out after assembling it and then reattach the pump with its gauge around 20 minutes later to see if any air has leaked back in.
Now Underwater Camera Stuff in the USA has produced a similar system at a much reduced price, and it works with almost any proprietary camera housing on the market.
You can even adapt a less expensive Perspex housing to accommodate it. It‘s called Housing Sentry.

The Design
The system comes as a bulkhead-connecting valve complete with a watertight blanking cap and a Mityvac hand-pump with a pressure gauge attached. There’s a short hose with an input fitting (I suppose that should really be called an output fitting, as it is used to draw air out of the housing).
There are two versions, designed slightly differently, made either of stainless steel or chrome-plated brass and anodised aluminium. The “posher” basic version attaches to the hose much as a BC inflator does, but miniaturised.
Both versions work in the same way, and in each case the blanking cap is on a little chain so that you don’t lose it.
Bill Libecap, who sent me the kit to try, asked me which housing I wanted to use it with. My own housing has an unused port for an HDMI connection with a standard Nikonos-size threaded plug. This proved ideal, and the Housing Sentry valve screwed straight on, not forgetting the all-important sealing O-ring between the connector and the port fitting.
This also allowed me to use the Hugyfot Hugycheck built-in electronic system, which is supplied as a standard feature with that brand, to check up on the Housing Sentry’s efficiency without even getting my housing wet!

In Action
So with the camera safely installed in the housing and the main O-ring carefully greased and the clamshell shut, I attached the pump and pumped the housing down to 10in.Hg.vac. on the Mityvac’s gauge. I chose 10 because it’s easy to remember!
The flashing green light of the Hugycheck electronic system confirmed that a vacuum had been pulled. I waited half an hour and reattached the pump (the Hugyfot’s green light was still flashing).
To me, this is the point where there might be a fly in the ointment, because a little air inevitably escapes back into the housing from the pump when you reattach it.
The instructions say that provided the gauge does not drop more than, say, 0.5in.Hg.vac, everything should be OK.
Unfortunately, there is no in-water monitoring available to let you know that the vacuum is being maintained during the dive. You just check that the vacuum pressure has not dropped before you dive. However, as the pressure sensor inside the Hugyfot housing continued to keep the green light flashing, I knew I didn’t need to worry about that.
After the dive, the vacuum makes the housing impossible to open, so you reattach the pump to release the pressure.
If vacuum pressure drops in the interval before diving, you have got a leak. This will
most likely be caused by an ill-positioned main O-ring, or fluff, dirt or a hair on it.
Take the housing apart and reassemble it, being thankful that you still have a dry camera.
I would have given the Housing Sentry top marks if there had been some way in which it continually monitored the vacuum pressure without refitting the pump each time.
Bill tells me that by the time you read this Underwater Camera Stuff should have stocks of a more expensive electronic version called the Housing Sentry Complete.

Applications
Underwater Camera Stuff currently offers seven installation options for all versions of the Housing Sentry. In addition to the option for Nauticam, Subal and Seacam, there is an option to attach the Housing Sentry valve to an unused half-inch unthreaded bulkhead such as you might find on an Aquatica or Sea & Sea housing, or another to substitute it for an unused Ikelite control, or to fit it to a Nikonos connector in the way in which I tried it.
You can replace an Olympus electronic strobe connector, provided you don’t need it, or you can cut holes in any aluminium or acrylic housing if you have the skill and facilities to do so.
One final word: If you are travelling abroad, put the pump into your checked baggage. You don’t want to be questioned about it in the carry-on security check. Mispronouncing the word “pump” or a hard-of-hearing agent who thinks you said the fatal b-word will see you arrested and even imprisoned in the USA.

COMPARABLE AFTERMARKET VACUUM LEAK TEST SYSTEMS TO CONSIDER:
Backscatter AirLock, US$399, www.backscatter.com
Leak Sentinel electronic, 200 euros, www.vividhousings.com

SPECS
HOUSING SENTRY BASIC US $290
HOUSING SENTRY ECONOMY US $229
CONTACT www.uwcamerastuff.com
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