Hi Mike,

As long as you are doing flood and drain, I don't believe it makes much difference how you fill the beds; for they will get the nutrient rich water throughout. If you are going with continuously flooded, however, it seems like an even fill around the perimeter would be best.

On our square beds we use a perimeter fill (extra pipe) with four openings, one on each side, and a siphon in the middle. On our elongated narrow beds (narrow so they can be reached across if placed against a wall) we placed the siphon as close to the end as the grow bed design would allow and feed the water in under the lip of the opposite end, which spreads the incoming water a little.

By the way, we used to have three inch outer shells on our siphons but found them to be a little too small to get your hand down in for root cleaning so we went to four inch shrouds. They takes up a little more GB space but I believe is worth the trade off to be able to put my hand all the way to the bottom when the stand pipe is removed, which is now much easier to unscrew.

The stand pipe can now be easily changed out and a shorter one can be inserted if it is decided to use that bed for root vegetables. It seems root vegetables don't like lots of water on the large part of the root and will put down a fine root to the nutrient rich water, which seems to suffice. We discovered this by accident when on our second planting the bed with our root vegetables had its inflow valve open to much and the siphon wouldn't break, so the water level stayed low. We didn't notice this until we had some of the largest and best tasting radishes I'd ever seen, and I normally don't like radishes. Our first root vegetable planting failed to create a large root mass as they were in the water a lot. Not sure how that all works but that is what we discovered.

These siphons are simply modified toilet flanges (the kind with no hole in the bottom) with an added hole for the bulkhead which passes through the flange, then the thick washer seal, then through the bottom of the GB and then the bulkhead back nut. This arrangement holds the flange in place as well as the shroud when snapped into the flange. The flanges are made to support either a three or four inch pipe, so the change was only to the shroud and its rubber cap. The shrouds have horizontal slits cut in them with a chop saw from near the bottom to the height of the lowest point of the desired flood and drain. It is not necessary to drain all of the water out nor is it possible. I believe that draining only half the water our with each cycle is ample. This keeps the fish tank water height from varying too much. All components can be purchased at Home Depot accept for the bulkhead.

Sorry for the ramble,

Oliver