Known to be true: chipmunks love drain pipes!
Obviously, an open pipe attracts rodents.
That didn’t matter with a three-foot pipe attached directly to the downspouts, but, as part of the driveway project, I routed the house storm drains and wall footing drain pipes about 20 feet down from the new retaining wall, with the two joining into a single outlet. There’s a cleanout plug on the storm drain line, but the footing drain consists of about 50 feet of corrugated and perforated tubing that would be just about the finest possible chipmunk habitat.
In principle, one would simply glue a grate into the final fitting and be done with it, but leaves from the gutter will pack behind the grate, so it must be removable. Leaving the grate loose means it’ll pop out at the slightest provocation and, most likely, roll another hundred feet down the driveway into the street.
Rather than coping with that, I drilled a clearance hole in the elbow and tapped a matching hole in the grate:
I have a few white nylon 1/4-20 cutoffs from the bike fairing clamps, so I wrecked the threads on one and jammed it into a black nylon thumbscrew:
Now, of course, the critters can still climb down the drainpipes from the gutters and set up housekeeping in the plumbing, but I’m not putting grates where I must climb onto the roof to clear them. A chipmunk dropped from two stories will scamper away; I’d never walk again.
We shall see how this works out…