The problem is that the suitcase clamps can't do this, so the housing vendors rely on an incomplete face seal and let the water pressure complete the seal. To me this is a poor trade-off and explains the tendency for housings to flood in the rinse tank.
I just want to set the record straight, the so called “suitcase” latch are actually designed to preload the O-ring to a set amount of pressure, we use 45 lbs, but it could be anywhere from 30 to 70lbs, depending on a manufacturer preferences. This preloading will be compressing the o-ring to a depth equivalent of about 100ft of ambient pressure, and that is before it even touches any water. Sorry but, the claim that “suitcase” clamps do not offer a complete face seal or are just holding the front and back together in wait of ambient pressure is not accurate.
If you ask me, so far as I can tell, I have yet to see a “faulty or inadequate” design of housing closure system among the group of housings manufacturers that tends to your underwater photography needs. That group would include us as well as our competitors past and present. No matter what the method, be it side sealing or compression sealing, a housing manufacturer decides to use for sealing and securing their housings, they will be staking their reputation on it. So c’mon, I mean, this industry is pretty Darwinian, if you are ill adapted for the task, you will simply become extinct!
O-rings and their roles in protecting our equipment from ambient pressure is basic elementary knowledge for anyone involved in manufacturing underwater equipment, No one would seriously think, that if a closing system was incompletely, or poorly, doing its job, especially with all the method of sealing a housing available, that a manufacturer would keep using this type of closure for decades. There is a substantial amount of photographic and video manufacturers using these “suitcase” latches successfully; they are also commonly used as a mean of closing up and sealing many of the military and scientific equipment that requires ambient pressure protection.
Adam’s got a point when he says that floods occurrence is normally due to O-rings not being located properly, being damaged or dirty, they do not spontaneously fail unless there is some interference of some sorts involved.
Before even pumping up the vacuum in a housing, A simple and very efficient way of testing to see if the main O-ring is properly sealing is to gloss up the O-ring, make sure the mating surface is clean (both of which you should do all the time anyway) and simply close the back, clamp down the latches and open the housing again, you should see a clear foot print signature of the O-ring on the mating surface (see picture). At this point, what can I say, it is the user’s responsibility to check and that there is no obstruction, nicks or scratches on the path of the foot print signature.