46 CFR §171.119

1. (a)If a vessel operates on exposed or partially protected waters, an opening port light is not permitted below the weather deck unless—
   1. (1)The sill is at least 30 inches (76.2 centimeters) above the deepest subdivision load line; and
   2. (2)It has an inside, hinged dead cover.
2. (b)Except for engine exhausts, each inlet or discharge pipe that penetrates the hull below a line drawn parallel to and at least 6 inches (15.2 centimeters) above the deepest subdivision load line must have means to prevent water from entering the vessel if the pipe fractures or otherwise fails.
3. (c)A positive action valve or cock that is located as close as possible to the hull is an acceptable means for complying with paragraph (b) of this section.
4. (d)If an inlet or discharge pipe is inaccessible, the means for complying with paragraph (b) of this section must be a shut-off valve that is—
   1. (1)Operable from the weather deck or other accessible location above the bulkhead deck; and
   2. (2)Labeled at the operating point for identity and direction of closing.
5. (e)Any connecting device or valve in a hull penetration must not be cast iron.
6. (f)Each plug cock in an inlet or discharge pipe must have a means, other than a cotter pin, to prevent its loosening or removal from the body.