I have this idea but I don't know if such thing exists. Basically I want to build a switching / valve mechanism that connects to garbage disposal output so that I can flip it to and point the grinded waste to either a bucket down below the sink or directly to the drain pipe.
My pipe is just PVC. Is there such a switch/value product other to do the split?
Absolutley there is such a thing. you want a "greywater diverter" valve.
Many styles are available. but I recommend you pick a different location for the bucket as forgetting the valve could get messy and expensive.
You would probably be better served by putting the compost material in the bucket directly and skip the complex methods.
What happens if you leave the diverter in "compost" mode, and someone (sleepy you at 3am, a guest, etc) just starts running water? You'll end up with water in your bucket, potentially overflowing into your cabinet & ruining it and damaging the floor below.
What happens if someone has the diverter in "waste" mode and starts throwing large chunks down the drain thinking they'll go into the compost bucket? You'll end up with large quantities of mostly solid waste in your plumbing lines and end up with a clog.
Keep the bucket under the kitchen sink if you want, and to make it easier, devise a large handle that makes it easy to open the door with your knee or with wet, messy hands so you can open it and toss stuff directly into the compost bucket.
Leave the plumbing and the garbage disposal to water and the small quantities of solid waste they're designed to handle.
Better yet, compost your food waste with an outdoor worm bin using red squiggler worms to digest the food compost into a wonderful soil amendment. Google "vermiculture". You will use your garbage disposal less and less. I can provide easy diy instructions in another question, perhaps in gardening section.
