I like to use "through holes" (also called "bulk head fittings"). The ones I mostly use in-particular, I find in the electrical department at Home Depot, and are about $2. Located with all the connectors and fittings for electrical conduit. That particular one fits a 5/8 inch tubing, but it's not hard to step down a 5/8 line to a 1/2 inch line. But through holes come in lots of sizes, and are used in many different industry's, and for many different reasons. They usually come either with threaded or barbed ends.

Here are some I quickly found online to give you an idea what I'm talking about.

PVC and ABS Bulkhead Fittings
An Improvised PVC Bulkhead Fitting for Liquid Storage Tanks
BULKHEAD FITTINGS
BARBED BULKHEAD FITTINGS
Bulkhead Fittings Wholesale

i just use your normal pvc fittings. Male piece, female piece, washers, and o-rings.

I haven't been able to find male PVC fittings that aren't tapped yet. I wish I could because I would like to do that in some situations too, at least without needing to find the right size spacers also.

I use one PVC Male Adapter Thread x Socket and a Threaded PVC Coupling PVC and just go from there (unless I need something special. They seem to have them at most hardware stores and in most sizes.

That looks like what I've tried in the past, except in white. Although I would really need to try and screw the male and female ends together to tell if it's tapered. The tapered ones don't go on all the way and leave a gap you need a spacer for. Unless the material it's going through is about 1/3 to 1/2 inch thick. Their designed that way, to get tighter the more you screw them on (in order to make it water tight). But they leave a gap when going through relativity thin plastic like a 5 gal bucket, and I always have a hard time finding the right spacer that's just the right thickness, as well as wide (to fit the shaft part without being loose). If it's too thick they wont screw together tightly, and too thin they will still leave a gap or be loose.

Thanks everyone, I have enough ideas to get the job done now.

Joe

HH;
This is the Male piece you need.

This is the female piece you need. Note: you have to take out the neoprene gasket in the female piece to get it fully tightened.

I believe This is the gasket you need.
All from lowes. I've been using them for years.

Thanks grizzman,
Those look different than ones I have seen with the PVC connectors at our store. But I can copy the pictures and the Lowe's item and model numbers into a text document. Then I can take it with me next time I go out by Lowe's. Given I have the item and model numbers, I know if they don't have then in-store, they can have them shipped from another Lowe's store at no charge. Thanks again, that's a big help...

Thanks to all. I got the water tight parts at Home Depot in the electrical department. What I liked about them was that they had the with a right angel, and the barbed end fit the 1/2" irrigation tubing I bought 50 feet of, for less than $10. They also had a T so I could connect the two trays together and feed them through one 1/2 pipe. I could cut the inside near flush. I needed that because I plan for gravity to back the nutrient back into the holding tank in the ground when the pump shuts off. I put a second connector for over-flow on each tray, they will hit a T and feed to one 1/2' pipe back to the holding tank. The good thing was that I bought two O-rings that will go over the threaded end on the inside of the tray, then I will thread on a 1/2 pvc connector that will let me set my overflow by the length of pipe that I pressure fit into the glue end. I will upload a picture when I get it all together. I have a greenlee metal punch that makes a perfect 1/2" hole, and those threaded parts make a water tight connection just by how they screw into the plastic, so the O'ring and nut are a added bonus.