drains check valve - OpenScad

These types of check valves are used on board of ships to drain hatch coamings and to prevent sea water from going inside the hold. And as usual small parts are more vulnerable - blind cups are often missing, balls are broken. Sometimes we have to replace whole valve. And any supermarket is too far.

Here is my replacement. Dimensions and threads are customizable.

Original halves are screwed together, but I think that 4 brass wood screws should be enough to keep halves together.
Blind cup has 2 options - regular and with drain plug.
Second one is usefull during hose test (one of method to check tightness of hatch covers). Drill the hole in cup of clear plastic bottle, put the drain plug through and screw everything (check valve, blind cup, drain plug, plastic bottle). Water from coaming drains, going throught check valve is collected in the plastic bottle showing how big the tightness problem is.
When You use this one during final test of hatches in repair shipyard, be sure the