WIN!: the MC18-B is water proof to 220 feet...tested!

High pressure? No problem! I have to admit, the result surprised even me. I made this pressure tank months ago when I was building dive lights and never got around to testing one of my land lights. I was hoping for 30 feet of water resistance. That would already beat most lights that are not "dive-rated." Long story short: I tested three lights at 220 feet for 2 hours! Tomorrow I'm going to take one light and test it to failure or 300 feet, whichever comes first. 300 feet is equivalent to 130 PSI (10 PSI shy of the pressure limit on the test vessel). You might want to stay tuned for this one :) 

95 PSI = 220ft of water (black hand).
The red hand is a "set hand" like on an alarm clock. 

Nearly every manufacturer that I'm aware of rates their lights (excluding dive lights) as "water resistant" or "weather proof" but little else. This means you can take them in the bath tub or walk your dog in the rain...but that's about it. Some manufacturers list a rating called IPX-8: "The equipment is suitable for continuous immersion in water under conditions which shall be specified by the manufacturer." Most flashlight manufacturers fail to indicate what those conditions are even though they list an IPX-8 rating...so their rating is essentially meaningless. I'd guess they are still fine for bathtub duty though. 

Part of the reason for testing these lights is so that I can articulate the "conditions specified by the manufacturer" instead of throwing around fancy industry codes that no one understands anyway. Something like "Waterproof to xxx feet." 

For details on the tank and testing procedure, read on after the jump...
The tank is a stainless pressure vessel that I found on Ebay...the bringer of all things. I purchased the pressure/depth gage from McMaster as well as the ball valve, and safety over-pressure valve. The tank is about 90% full of water. I drop the lights in, hook it directly to my air compressor (regulated to 95 PSI), and crack the ball valve open to slowly bring the tank up to pressure. 

I started at 30 feet and crossed my fingers for 30 minutes. Then, release the pressure and inspect the lights for water ingress. If they look good...another 30 feet of depth and another 30 minutes. Eventually I maxed out my compressor at 95 PSI and decided to leave the lights in the tank for the rest of the day (the reason for the 2 hour test duration). Tomorrow I hope to up the ante and take at least 1 light to 300 feet. I expect the lens to shatter at that depth, but that's just a guess. If it holds for 30 minutes I'll try leaving it at depth overnight or something crazy like that. Let's see what happens!