Here is the design that i used for my hopper box. I designed this myself, and you are free to use it and change it how ever you like. The current design uses a industrial air conditioner vent as the grate, but you may need to find something else or design something yourself as a grate. The air conditioner vent will get blocked by some rocks and can be tough to get them out. The box itself works great though. I think I changed the opening in the bottom to make it a little bigger, and may have changed the angle from 45 degrees to something larger to increase water flow. I will post some pictures of my setup in a later post.
This design should be build with aluminum sheet metal and has tabs to be riveted with aluminum rivets. You can easily find you material at Home Depot, Lowe’s or tractor supply. If you decide to use one of these stores, you can save a little money by opening a free account at Mr. Rebates. You can save a few percent buy buying the stuff online using their links that will add up over time. I think there are about 2400 different major stores that you get discounts at by using them.
My plans are in PDF format in the link below that says Hopper Box Plans. I have attached a .jpg image of the first two of 6 pages so you can see them on this page.
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