This is a replacement, as the original was destroyed by the sun.
It screws onto the can and the cover also comes off for cleaning. I printed mine in translucent blue PLA, so trash inside can be seen and cleaned out. The brown line in the close up is algae, blocking one of the holes.
This uses the Screw Library by syvwlch for the threads to the can.
The cover is just a snap fit, no threads.
I did make some small improvements after printing mine, so yours will be better:)
Test print just the threaded ring to see if it fits your water can. Look at the top of the scad file and you will see it is just a matter of uncommenting one line and commenting out another. If not, adjust...
The lid is a tight force fit, it snaps on. Even so, mine leaks anyway. My print is a bit rough though, I find that translucent blue to be challenging. A smooth print will probably not leak.
Note, should you be so inclined as to put more holes in your cover, know that too many holes do not work well, air goes in the upper ones, instead of water out. This cover has 31 holes, the original had 28. That said, you can play with the for loops that generate the holes and come up with some interesting patterns.