Flowing Nutrient to the Channels

When I first started doing NFT (Nutrient Film Technique) hydroponics I would flow a large amount of nutrient through the channels by connecting a flexible 1/2 plastic tube from the pump and running it all the way to the end of the channel. This made for a lot of flow. One thing I noticed is that the tomato plant roots grew at an incredible rate and wound end up coming out the ends of the tube at the tank end and grow into the tank. Really long roots. By the end of the Summer in some years the roots would be so thick that the nutrient would actually start over flowing out the sides of the holes in the channels for the plants. That was just too many roots. I tried cutting down on the flow and that actually seemed to reduce the root growth.
In the picture you can see the way I feed my channels now. I run a piece of 1" PVC parallel to the channel (a piece of 4" diameter PVC with 3" holes on 17 inch centers) and drill a 6mm hole and thread a 1/4" piece of plastic tubing to a hole at the end of the channel. This restricts the flow and delivers plenty of nutrient to the plants. The result is roots that still grow rich and healthy but don't totally fill up the channels. It works really well.