Don't waste your money on expensive valves you will never use. These hoses are usually heavy duty and are under very little pressure (1/2 psi). Change the hose clamps once in awhile and check that the through-hull is bronze not brass. Electrolysis can eat away the zinc and leave the copper very weak. Replace the t-hull and hose every 10 yrs. or so. If you are nervous carry a spare piece of hose.

:: 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?