Don't worry, I did use a new disposal!
Though for a moment I eyeballed one on the shelf at the local ReStore... I figured it realistically *could* be cleaned sufficiently. But that if I ever admitted that I'd done that I would never live it down.
The base is a
large rubbery plastic planter I found at Menards.
The disposal is a
1hp with stainless guts I found at Home Depot. Went with that because I read smaller ones may struggle with circulating so much ice.
I cut a 3.5 inch hole in the bottom of the cooler, and upturned planter. After digging some of the insulation out of the bottom of the cooler, I was actually able to use the disposal's hanging mechanism to clamp the cooler to the planter with no glue required. That was handy with making slight adjustments in centering things together while assembling the plumbing. It did take my wife and I working together pushing and pulling the disposal mechanism (plus balancing the upturned cooler on a 2x6 chunk to help put some upward pressure on the sink ring) to get the snap ring in the groove, and we just barely did it, but we did. Thankfully the planter was just flexible enough to make it work. Using the planter made the project much quicker than building a box out of treated plywood, which was the plan if the planter didn't end up working.
You'll need a 1.5" sink plumbing outlet flange to replace the outlet flange that comes with the disposal to make it come straight out rather than curve down. Though I did cut enough off of it, you might be able to use the included outlet flange after all, cutting the 90 off. A 1" Fernco slips over that well enough to adapt it to the 1" PVC pipe.
So the 1" PVC exits the disposal and through the hole in the planter. Goes into the T. I chose to order the clear section of PVC (I ordered 2 feet and had about 6 inches left over) because it is fun to see the margarita circulate, and also you get a level gauge to know when the party is about to be over.
One improvement over my friend's machine is the valve (while planning the project I looked his over very carefully and we discussed improvements). Often you see standard 1" PVC ball valves on these things. He said it is just easy enough to open too far and difficult enough to close fully that lots gets spilled and he ends up having to babysit the machine and help. So I used a bushing that allowed me to screw in a 1/2" valve to slow things down. If it becomes necessary, you could run the motor while dispensing to give the mix a bit of a push.
I wanted to be able to disassemble things if it ever became necessary, so I added a screw fitting at the top of the return line. So if it ever becomes necessary, I will be able to unscrew the return pipe at the top and and unclamp the Fernco at the bottom and remove the whole return and valve assembly. I will have to redo the silicone seal up there in the cooler but that's it.
I don't have it yet (Jeff Bezos will deliver on Saturday) but I decided to use an air-activated push button switch since this will be next to the pool and wet hands a bunch. So i do still need to drill that hole and set it up but that'll only take a few minutes.
A 1 1/4 forstner drill bit was used for the holes in planter and cooler. With that and a touch of enlargening with a knife, I had a very tight fit for the pipes and they are well supported by that.