Gather your Supplies!
I used three (3) of the 35 pound Tidy Cat Litter containers. They should all be the same style; I use the ones with the folding lid, not the solid lid.
For the bottom level drain, I bought a CPVC 3/4 in x 1/2 in coupler, as well as a 1/2 in x 3/4 in bushing, along with some gasket material to make a tight seal for the drain.
Use a primer and cement designated for use on CPVC.
1/2 in CPVC pipe, whatever you have around the house. If you don't have any, just buy the smallest length you can get. Generally, they will sell it in 2 ft. lengths at Home Depot.
One water valve. I use a gate valve because it is less expensive, but you can use any ball or gate valve of your choice, as long as it is 1/2 in CPVC.
I use paddle drill bits for this application. The plastic in the litter containers are thin enough these seem to work best. The first is a 7/8 in bit, for the drain, and the second is a 1/4 in bit for the air holes and level transitions.
Step 1: Prepare the Bottom Level
First things first. Before you worry about the worms or their homes, you need a way to get rid of that excess moisture, also known as "Worm Tea." Your worm farm will need to be damp, and during the decomposition process, liquid will be produced. It will not necessarily be a large amount, but it will be enough that you will want an easy way to drain it without lifting the top racks out every time.
There are two ways to install the drain. You could place it in the side-wall, however the liquid level will then need to be at least a half inch high before any will drain out. To prevent this, place the drain in the bottom of the container. This will necessitate lifting the container at least six inches off the ground. 12 inches is probably better.
1. Prepare your gasket by taking the bushing and setting it on the gasket material. (You could skip this step if you have an appropriately sized O-ring. It would probably do just as well.) Trace a mark around the smaller end of the bushing, and cut a hole through which to place the bushing. You can cut around it as well to make a ring shape, but this is not necessary.
2. Turn the litter container over onto its lid and as close to the middle on one side as you can get, drill your hole. I like it closer to the side, since this is where the valve is going to be, and it is more convenient. After drilling the hole, use a pipe reamer to get the jagged plastic off the rim of the hole. If you don't have a reamer, you can trim the edges with a razor knife or some sandpaper. I will sand the edges even after using the reamer.
3. Use your CPVC primer on the bushing and reducing coupler and wait to dry. (It will dry fairly quickly.) Place the bushing and gasket on the inside of the container and hold in place. Use the CPVC cement on the exposed portion of bushing and place the reducing coupler on it, holding it in place for several seconds to get a good seal. Do not twist it after placing it on there, as this may affect your seal.
4. Cut a two (2) inch piece of 1/2 in CPVC pipe. Primer the outside of the pipe and inside of the exposed coupler. Cement the pipe into the coupler. Do the same for the gate valve, making sure that the directional arrow on the valve is pointing down. If you choose, you can place another pipe at the end of the valve to reduce splash.
5. On the two short sides, three inches from the bottom, place a screw in the middle of the container. This will allow plenty of drainage space without leaving too much of the upper levels exposed.
6. Place your container on an elevated setup. You can use cinder blocks, wooden blocks, or anything that will elevate the container to the height you need, as well as provide stability.
Step 2: Additional Levels
This is where your worms are going to live. Each of your remaining levels are going to be exactly the same, so I'll only go through the process one time.
1. Pull the lid off. Turn your container over to expose the bottom. Using the 1/4 in paddle bit, place 10-15 holes in the bottom of the container. You can put them in nice, orderly rows, or just put them anywhere. It honestly does not matter. Don't overdo it, though, because you don't want the whole bottom missing.
2. Clean up the edges of the holes with some sandpaper. You don't want your wriggly friends to get scraped up going from one level to the next.
3. Take a look at your litter container. There is a lip where the handle attaches to each side. Using your 1/4 in paddle bit, place holes in this section, and in the section directly above it. You don't need too many, maybe 3-4 on each corner. Your worms do need fresh air, and so does the decomposition process.
4. Clean these holes up as well, just to give it a clean appearance.
5. You will need at least two of these, possibly a third if you want a spare. The top-most level will need the lid. Do not place any holes in the lid, and keep it snapped shut while you have worms in there. You will need to be able to remove the lid when you empty your new worm-casting soil from the bottom level and put it back on top. This is why it is important that all of your containers are the same; the lid needs to be interchangeable.
Step 3: Worm Bedding
This step is one of the most important. Now, you have your bottom level where the tea will be drained. You have the second level where you will introduce your first batch of worms. General guidelines for worm bedding/food can be found on a dozen websites around the internet. I will give you what I've found to be the best.
1. The first layer should be some shredded paper. You can use newspaper, notebook paper, whatever. If you have a shredder, use the waste from that. (Try to remove any metal or plastic bits before you feed it to your worms. It won't get eaten and you can't use them for your soil.) Don't soak the paper, but get it damp after you shred it, but before you place it in the bin.
2. The next layer is your food scraps. **Never feed your worms meat!** Also, stay away from dairy or bread. Worms don't eat them, and they decompose differently, and can attract flies and other bugs you don't want. Vegetable scraps, banana peels, citrus peels, onion peels. Anything organic. Coffee grounds, with the paper filters are good. Tea bags, as long as they are paper, not plastic. (The metal staple in these should be removed.)
3. It is important that there is not too much of any one thing. Too much citrus, too much coffee may be detrimental.
4. On top of the food scraps, I'll throw in some loose, dry dirt. Get some dry organic yard scraps to place on top of this. Dry leaves, if it's that season, or some dry grass, after you've mowed your lawn; it can't be green. You can also dry out clippings from your garden or landscaping. Weeds are fine, too. My suggestions here are just pull them, and leave them in the sun for a day or two, then you can add them to your worm farm.
5. Wet the top of this mixture with a watering can or a mister from a hose.
6. Cut a piece of cardboard to fit the inside of the container. Wet the bottom of it, and place it on top of everything else, ensuring a tight fit. You don't want the worms trying to get out if you'd rather they stay with the food. This cardboard will eventually decompose as well, but you may be able to use it three or four times.
Step 4: Adding Levels
Depending on how many worms you have, and how shocked they are at being relocated, your scraps could disappear fairly quickly. Every now and then, loosen up your castings, as they can become compacted, and add scraps underneath your cardboard barrier. Eventually, your castings will be solid, and no paper or food scraps will remain. As the amount of castings build up, you will want to use these for your gardening needs. So, we need to add a layer so your worms will find a new home.
This is why you need two or three containers with holes drilled in the bottom and air holes in the top. Remove the lid completely and then remove the cardboard. Place an empty container on top of the existing castings. Go back to the previous level and create a new home for your worms exactly like you did before. Place the used cardboard on top of your new bedding, and place the plastic lid on the container. Then.......wait.
Give it about three or four days, and your worms will migrate up to the new container. If you wait a week, you may not have to take many out manually, because really, some or your worms will take longer to migrate. Remove the top level, then remove the middle level, replacing the top level back into the bottom level to continue with the composting of the new bedding. You will still want to sort through the castings to get as many of your wriggly friends out as you can, as well as getting out anything like a scrap piece of paper or portion of a banana peel that hasn't been completely eaten. Add all of this back into your new bedding, under the cardboard.
Step 5: You're Done!
You've done it. Keep adding scraps and before you know it you'll have more compost than you can handle. Remember, once your worms get established, they can reproduce fairly quickly. That means you'll need to continually supply them with food and scraps to create your castings. At some point, you might even need to separate your worms into a new farm, so you can have two. Or, you can build one for a friend and gift them their first set of worms.
Let me know if you try this and how it works out for you. The first one I built I let sit for too long and ended up losing half my worms. Got to keep it in the 60 to 80 degree range for the worms to flourish. Mine were in the garage all winter, and I'm not sure they ever got above 60. Lessons learned. Throw any questions in the comments section and I'll try to answer them.