using an external pump

[Sigh]

Random comments and questions:

Regarding using an external pump (PVC ebb and flow) and needed to get the system to drain back to the reservoir: If done correctly, a tap can be placed anywhere over the reservoir and a small air/drain hole can be drilled on the bottom side of the PVC. The pump should have more than enough capacity to fill the system 'til the overflow takes over and when the pumps quits, the system will gravity drain through the tap hole back into the reservoir. By changing the size (number?) of holes, drain time can be changed. Too fast? Tape/glue a hole shut, drill a smaller hole. A LOW POINT should be found (or made) to help guide the water, but if you build a little "dam" around the drill hole, you can keep the nutrient from running up and down the horizontal PVC if it becomes a problem.

Regarding larger systems and proper filling, in addition to placing the inlet in the middle of the system, if the ends are also joined, then filling will be aided. In long/large systems, I would think that the distance from inlet to over-flow and from over-flow to one/both ends would effect how (well? fast?) the system fills. Then again, since the system fills for 30 or more minutes at a time, this is probably not a problem. Sigh. I just figured it out.

Ron (or anybody): How long does it take your system to fill ('til the over-flow takes over) and how long does it take to drain?

[Ron]

Each of my systems fill at different rates because of the different size pumps and the number of bottles I am filling.
So as Einstein said "it's all relative."