I think Im going to start off with a slightly different approach than the horizontal tubes. I dont think I really have room to do that efficiently in my tiny tent, plus I really want to try the drain to waste thing. The idea of NOT having to mess with constant PH and EC adjustments is really appealing.
Here is a crude flow diagram for how I think I want to set it up. Id appreciate any feed back on it.
I have left off details like couplings, T’s, shut off valves, and minor parts to drain the accumulator and rez, etc. I also didn’t draw in the pressure gauge. I may go with two – one before and one after the pressure reducer. Im going to need to monitor, and adjust both of those while dialing things in, and two gauges will make that easier. Gauges are one of the cheaper parts. Im also considering one of those inexpensive BluLab dual probe TDS meters to monitor the TDS of the runoff, and the supply water.
From my reading, it seems that there is a close interaction between almost all the parts. Which, and how many heads you choose, for example, depends on the pressure ranges available from the pump and cutoff switch, the root chamber size, and shape, pressure differentials at the reducer, where and how many solenoids, etc etc.
I don’t really fully grasp all the theory behind this, but I think I am kind of, more or less, almost in the ball park. I’ll post my preliminary parts list later.
This is how my tent will be laid out.
My grow tent is in my hobby room, so space is limited. Its 28”deep x 38” wide x 48” tall - inside dimensions. It sits on top of my wood work bench which is 30” above the floor. My current rez, pumps, carbon filters and misc stuff is all under the bench at the moment and most of that will need to move for the new layout.
My current thinking is to cut a 24” round hole in the top of the bench/floor of the tent, and hang a 30 gallon fabric smart pot below the table. The cut-out will have an insulated foam top on it with cutouts for net pots, to start and grow clones or seeds. I will only grow a max of two plants at a time to harvest from now on – in a SCROG setup. I may start several seeds or clones, and then just keep the two best ones to finish the grow.
This layout will keep the root chamber mostly insulated from hi tent temps and should allow me to keep root chamber temps at no more than the low 70’s at most. I really like Atomizer’s ideas of doing HPA drain to waste as well as his ideas for using a fabric root chamber that can air prune the roots if/when they get to the sides or bottom of the chamber.
The fabric pots I’m looking at are 30 gallon pots 24” in diameter x 16” tall. I can easily make them taller by cutting up, and stitching on another pot, so any height is possible as long as its less than the 30” I have under the table. That means I can have a circular root chamber 24” in diameter, with fabric sides and bottom, that is anywhere from under 30 gallons, up to maybe 50 gallons if need be, for no extra money – the pots come 5 to a bundle. These pots are not quite light proof, so a light shield, that also allows for good air circulation outside the pots, will be necessary. The air circulation will be dry room air for evaporative cooling of the chamber. Also, you need dry air to prune the roots or they will just keep growing through the fabric. I already have materials for that and the catch basin.
I am still almost clueless as far as how many heads, where to place them, how to point them, cycle times, etc. Ive been ‘doing the math’ on spray times, flow rates, chamber volumes, etc, but Im not at all confident I have done it correctly. I’ll post those later. For the moment, I am thinking two No Drip Hypro heads will be about right – maybe – but that is really vague guess work on my part.
Im trying to come up with a list of parts that will keep me under $300 - preferably well under - but Im still working on that.
Its obvious after some searching, that HPA, and especially AA, is not for everyone. Very few people are doing it from what I can see. There must be a reason for that 
