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Old May 31, 2013   #7
rwsacto
Tomatovillian™
 
Join Date: Sep 2010
Location: Sacramento CA
Posts: 288
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Quote:
Originally Posted by SIP Gro-Tubs View Post
Rick

.......
Aeration holes are another laugh. Thats a marketing gimmick.

How does the air get into the bottom of the bucket, once the water is wicked up to the media in the first place.

What force will react with air that isn't moving, move it up thru the aeration holes.

Air fills the reservoir void as the water level drops, thru the path of least resistance. That's either thru the overflow holes, or the fill tube.

I'm going to do a demo, of this tommorrow. you will be able to see the air moving up between the inside of walls of 2 buckets.

You will be able to see the air flowing thru the overflow drains, and the fill tube, when the reservoir is being refilled.

Terry Layman
Terry,

Thanks for the detail. Just to summarize (for my understanding) You have large drainage holes in the bucket wall above the shelf, overflow holes in the bucket wall below the shelf and no aeration/drainage holes in the shelf.

My understanding of container aeration is to provide oxygen exchange through diffusion at or near the bottom for the roots to breathe and to prevent anaerobic conditions in the media that will kill roots. Diffusion does not require "force" (moving air or water) to happen. It is driven by the difference of partial pressure of (in this case) oxygen in the air and in the media (gas as well as dissolved in the water). Diffusion will try to equalize the partial pressures. As the roots and bacteria in the media use oxygen, more will flow from the air into the media through the top of the media or through the aeration holes.

In your design, I believe what you call drainage holes are performing as the aeration holes. Therefore, your design works without holes in the shelf. A bit of aeration is probably also happening through the fiber wicks.

In Earthtainers and similar designs with no holes in the container walls and where the shelf is positioned above the overflow holes, I believe the holes in the shelf act as both drainage holes and aeration holes.

Without aeration (in the bucket wall or the shelf) I believe the SIP will still wick water fine, but the bottom will get stinky and the plants will perform poorly.

Volume equalization may be a more accurate term to describe the displacement of air and water in the reservoir. This is simple hydraulics and has nothing to do with drainage or aeration of the media above the shelf. This is what your demo will show.

My thoughts,
Rick
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