Fortunately, splice enclosures these days are built to survive almost anything short of a nuclear blast and, when properly installed, are all but impervious to water penetration. GR-771 ensures that this is so. Even if water were to find its way into a splice enclosure, it usually is not in sufficient quantity to cause any harm. A worst-case scenario would involve severe cold. If a significant amount of water freezes inside a closure where exposed fiber is present, the crushing forces of the ice could damage, and even break, the cable.
Many closures now come with built-in air valves for performing flash testing.
This involves sealing a closure, filling it with 10 psi of compressed air, spraying soapy water along the seals and then waiting. If, after 10 to 20 minutes, any bubbles appear at the seals, you ve got a leak and need to reseal the enclosure. Otherwise, you re good to go. Cope likes to water-test enclosures before deploying them in the field. He also likes the training offered by manufacturers.