Quote Originally Posted by davidstcldfl

On the horz ducts....what is the depth of water in them..?...and the flow rate through them..?
On the vert ducts, I noticed you removed what appears to be a plug/clean out. Is this where the water drains from the vert ducts..?
David, thank you for the compliments.

The horizontal ducts are 5 inches square on the outside, a little less on the inside. There is a 3 inch high (adjustable) riser on the drain end connected to a bulkhead on the bottom of the duct. The bulkhead has an outside protrusion designed as a barbed fitting. That protrusion sits in a hole in a 4 inch drain-back pipe that runs along the edge of the table just below the end of the ducts. This helps position the ducts on the drain end. The water enters on the opposite end of the duct through another bulkhead fitting on the bottom as well, with no riser inside. In future designs the input to the ducts will be through Uniseals.

We have yet to measure the flow rates on the horizontal ducts but plan to do so soon. The water feeding the manifold for the whole horizontal system is adjustable. Each vertical two back-to-back arrays has a single manifold up high and water flow adjustment to it. The flow in both horizontal and vertical ducts, to the individual duct, is balanced out by the ratio of the size of the feeder tube to the size of the feeder manifold. The duct feeder tubes offer some resistance to flow thereby balancing out the flow to each duct.

The drains on the vertical are the same bulkhead fitting as the horizontal, except they are located on the end cap with no internal riser. They also sit in holes in the drain pipe for location. The horizontal ducts are DWC and the vertical ducts are NFT. The service caps on the vertical ducts are missing because the hole is slightly too small for the caps and needs to be enlarged in order for them to fit properly. It has given us an opportunity to observe the water flow and root growth as well as any root interference with the vertical duct drain, which hasn't been a problem.

Oliver