I have read quite a few diy Nutrient Film Technique (NFT) guides online. Most are sparse on specific implementation details.
In an NFT setup, does the water need to pool in the trough or must all the water received at the outlet immediately drain away?
Referring to the cross-section below, should height h2 be close to zero (to immediately drain away water), or should it be a positive value (some water will pool in the in the trough).
To clarify the diagram: Water comes in from the inlet pipe, flows down the sloped trough and drains out the outlet pipe. Raising the outlet pipe above the bottom of the trough will mean water does not drain away immediately.