This is a simple vent I designed for a water storage barrel to keep it vented and prevent it from creating negative pressure inside when a pump is ran.

It is in 3 pieces, and shouldn't need any supports (if printed in the imported orientation,) but you can use them on the cap if you'd like. You may want to use a brim on the main body, but I didn't need too.

There are small slots on the underside of the cap to help prevent bugs and debris from getting in. To install, drill a 1"/25mm hole in the lid of your drum lid/bucket lid/IBC tote, and the rest will thread together. I would recommend using PETG, ASA, or ABS if the container will be outside in the sun and weather. The threads should thread together easily, but you may need to clean them up slightly if you're printed isn't calibrated well.

Note: The printed one in my pictures is a slightly older revision, I have tweaked it for the better.