patent pending.
Here's what I got. I think that many people have struggled with the schedule 40 six inch PVC and fittings. It is heavy, expensive, but definitely perfect for the original unit. With the 6" stuff, you can easily flow 1500-1700 gph through it, gravity feeding back to the pond with a 2" exit.
Here's what I want to suggest. I haven't tried it yet, but here's how it would be done. The original phoam phraxionator works by bubbles being formed through the crashing down through bio balls. Then, they "settle" out in the bottom chamber, trying to rise up as far as possible. If enough "dwell time" is maintained in that bottom chamber, the bubbles will reach up and out of the exit port which is the top of the "tee".
Here are the plans for doing a 4" unit. It is between $150-$175 to build a 6" PVC unit that will flow that 1500-1700 gph. I suppose that with 4" PVC, and a total gallonage of 3 gallons for the base of the unit (TEE, 18" run of 4" PVC and part of the 90 elbow), you could get around 8-12 seconds of "dwell time" in that bottom chamber for the bubbles to rise up and out.
Here's what I have so far, all items purchased at lowes:
$9.32 10 foot section of schedule 40, 4" PVC (for tower and base)
$3.47 green gutter trap (4") to keep bio balls in position above elbow
$9.57 4" schedule 40 long sweep elbow
$11.57 4"x4"x4" schedule 40 TEE fitting
$5.50 2" cheap schedule 40 ball valve
$4.52 2" PVC to go back to pond
$6.50 Fernco fitting to join bottom to top
$8.00 (2) 4" to 2" reducers
$50.00 approximate cost for the bioballs to fill the thing
$108.45
this SHOULD flow 800-900 gph pretty easily. I wouldnt flow more just becuase you want to assure dwell time in the unit.