Vacuum Leak Tests
This entry was posted on 6th April 2015.
Hugyfot and Nauticam, makers of camera housings, can supply them although it is an extra cost with Nauticam. There is also and after-market version called the Leak Sentinel that can be fitted to a wide range of housings. I can confirm that I always slept well in my cabin or hotel room while that little green light winked all night but I woke up with a start both times a red light began to flash. Green is good. A by-product of depressurising the housing is that the fittings are pulled tight and it is impossible to open unless you purposefully release the air-input valve. This means that both lens port and back are secure from accidental opening, for example in the fresh-water rinse tank, the site of many an accidental flood. I recommend you get a housing with a vacuum leak test or get one fitted and be released from the stress of waiting for a flood. After all, the saying goes, it’s not ‘if’ but ‘when’. John Bantin is the author of Amazing Diving Stories.In a career as an underwater photojournalist spanning twenty-one years I made around three-hundred individual dive trips. That amounts to more than six-and-a-half -thousand dives and virtually every one was made armed with a camera. Would it surprise you to know that in the process I flooded a couple? Well, you might think that two floods in that many dives is not a bad average but I can tell you that every one left me cringing. It’s not just the cost of replacing the camera but it’s the cost of missing out on the pictures while you are so disarmed. How do floods occur? Inevitably it’s a case of user error. All you need is a badly seated main O-ring or some foreign body to drop on to it just as you close up the housing and it’s “Goodnight, Nurse!” Putting the camera into its housing after reloading a freshly charged battery of a new memory card should be straightforward. It is if you are in a clean environment such as a well-lit hotel room and nobody distracts you while you do it. However the world is not a perfect place and substitute those idyllically serene conditions for the rolling deck of a dive boat in a rough sea or the gloomy interior of an island hut and operational accidents can happen. Some people take their housings into the sea for a first dive without their camera installed. I see little point in this since the housing must be cracked open in order to install the camera later and that is when O-rings might pop unobserved or a stray strand your girlfriend’s hair might float into the place where it can cause chaos. As a busy professional, I always carried a duplicate camera and lens with me in case the worst happened. I might see tell-tale bubbles escaping from the housing while underwater and lose a dive but at least I could carry on afterwards. To flood two cameras on the same trip is tantamount to carelessness. With a little compact camera in a transparent plastic housing you can always check for a leak by gingerly immersing it in the fresh water rinse tank. The sight of a few drops of water that can be removed before they do any real damage will reveal a leak. Not only that but a cursory examination of the O-ring in its groove through the transparent plastic will show up any break in the watertight seal. Not so with machined aluminium housings. One just had to be fastidious in preparation and have faith in your ability to do it right. A leak detector merely sets off a loud siren should it detect water inside the housing. By then it is usually too late and only adds more crisis to the drama as you try to get back to the surface before the precious camera inside is lost for good. Gradually I evolved from shooting on 35mm film to digital cameras and from there inevitably ended up working with full-frame DSLR cameras. These became so expensive to buy that there was no way I could warrant the expense of doubling up but technology came to my rescue in the form of the vacuum leak-test. Instead of testing for leaks with water that will ruin the camera should you get it wrong, you test for leaks prior to diving using non-destructive air. This is by and large how they work although different makes of equipment have intermediate lights using different strategies. After sealing up the housing with the interior full of air at ambient pressure, a warning light indicates that. It is red. You then pump out the interior through a special valve in the bulkhead of the housing using the pump supplied. Once the interior pressure-sensor determines that a suitably low pressure has been reached, the indicator light shows green. Green is good. Leave the housing for at least twenty minutes. If any air leaks back in, the warning light changes to red. Red is bad. If that happens you should reopen the housing and see what is amiss. It’s not a test of the housing. It’s a test of how well you closed it up after installing the camera. During the last seven or so years that I had the benefit of the vacuum leak test on my camera housing, I never lost a camera. Twice in that time I got a red light but was able to rectify the problem before it was too late. In previous years I would only have discovered the fault once I was under water with depressing results. I recommend anyone with a valuable camera to get the advantage of a vacuum leak test installed. Both