Plastic thru-hull fittings are found on many boats as drains for bilge pumps and air conditioners. The plastic will UV degrade over time and become brittle. Combine that with vibration from a clamped hose (and sometimes a short hose which puts sideways pressure) and failure will ultimately occur. I have broken several of these during my surveys and most were within one foot of the waterline. It took very little pressure from a screwdriver to separate the hull side flange from the hose fitting. This one had been cracked for a while and had been leaking seawater into the interior. Regular maintenance should include inspection of all your thru-hulls and replacement at the first sign of degradation.
Survey Tidbits #3
