Steve,

It's typically not the thru hull fitting itself that fails, but rather a hose or hose clamp that services the thru hull fitting. Since the thru hull fitting sits below the waterline, if there is a failure in any of the hoses that service the fitting, water will come in. The seacock is there so you can shut off that flow of water. They're a very worthwhile investment, so be glad you have them. You should open and close the valves every few months to ensure proper operation, and replace them if they don't operate properly, or if they show signs of corrosion.

-Claude

:: Hi

:: I have large valves attached to each of my cockpit drain
:: hose too and I have sat in the cabin looking at them
:: thinking what they might be used for. (When you might
:: want to shut them.) I can not see how they can protect
:: from though-the-hull failures. If the drain
:: through-the-hull fails, it will be of concern if it is
:: outside the hosing system--in which case shutting the
:: the valve would be pointless. If the cockpit is awash
:: with a wave, there is no need to close the valve then
:: either. The only reason I could see to close the valve
:: would be to take a bath in the cockpit, but I have
:: better places to that.

:: Someone spent some time and some money to install these
:: things.

:: I do not under stand why. Could someone explain this?