Commercial leak-detectors are based on the principle that a barometric underpressure (or: partial vacuüm) that is sucked in your housing with a hand pump, rises above a critical level. In that case a red LED on the detector starts blinking: probably a leak! If you already have a vacuüm pump, but no detector, a mini altimeter (basically a small barometer translating mbars in feets of altitude) can be very helpful. At least if you a have a transparent Ikelite housing. I use this little and cheap device ALTIMER ONE that I stick to the inside of the Ikelite housing. After the vacuüm is established (around 20 strokes) you read out the pressure in feets altitude (say 4000 fts). Giving you an objective indication of the pressure inside your housing. So you want to be sure that this reading doesnt change, say in the next couple of hours.
I haven't yet checked the altimeter reading during a dive. Its possible that the air pressure inside the housing may drop a bit, because of the decrease of water temperature (and cooler air inside the housing) with increasing depth. This will give you a higher reading on the altimeter. No reason to panic. Only a sudden lower reading on the altimeter means trouble. Apparently water is entering the housing, which causes a rise of the inside pressure Have fun!.
- marc1990 likes this