Very Impresive Laminar Nozzles

Yeah, he is using a custom made valve. It's simple enough though. It's just a tube with a small brass piece in the middle that when the water reaches it the water shuts it and creates a seal.

He has some pictures here about half way down the page.

I drilled a tiny hole in my nozzle, then the air bleed out that hole.
And when there is no air left, it just drip diny small drops of water out of the hole

And that is no problem because I have a catch thank that collect the huge amount of water from the Cutter anyway.

My concern with a small hole would be a speck of dirt clogging it.

I cannot understand why Mario used a brass slug. Surely a plastic slug would float better when the water comes up. Or a hollow plastic sphere.

My guess is that he is using brass because of it's properties. Plastics would have the same properties but may not last as long.

The thing is with this project. You tend to grab whatever you have around the house/shop that will work. It may not be the absolute best choice, but it works. I know I have done that a lot with my project, I guess I shouldn't speculate for Mario.

Another question. Is the typical low-pass filter self-priming? In other words one that is made from a vertical tube about 18" high with the inlet at the bottom and the outlet on the same side just above the inlet.

By self-priming I mean do you have to have an air valve in the top to let some air out so the top of the water is say 1" above the outlet, or can you just turn on the pump and once the bottom part fills with water up to the top of the outlet, does it compress the air a bit so that the top of the water inside the tube is just above the top of the outlet?

Yes, the filter is "self-priming." I don't know if you have seen the video on youtube about the filters, but you should check out parabolaqueous on youtube. Look for a video that is about 7 minutes long. It's really informative and he did a good job with it.