KoiGuy,
I missed this post until now (playing a little catch-up after spending all summer working at the cabin).
I really like the idea here. Very simple and inexpensive. Although I think that I might opt to omit the keeper pin and install a stainless steel or brass spring instead. If the spring was tapered or conical in shape, the wide end could rest upon the lip of the next fitting and the narrow end on the check ball. Such a spring would add some to the price, but I believe that it would make the assembly process easier and the valve more reliable especially in a horizontal or inverted vertical orientation. Otherwise (with just the keeper pin) I think that you would wish to install the valve vertically with the O-ring seat down and the check ball above and rely upon gravity and / or flow and pressure to fix the check ball to the O-ring seat. I would have to experiment with his original concept (with the pin and w/o a spring) and judge how well it functions in different positions.
One thing that I really did not understand was when he mentioned substituting the "bouncy-ball" or superball as the check ball. That is a very good idea as the rubber ball would seal without the O-ring as he mentioned. However, when he was explaining it, he cut the ball almost into a semi-sphere. Why wouldn't you simply leave it a whole sphere? The purpose of doing that elluded me.
Thanks for the post/video!
Catfishnut