FYI - real world example. I live in lambertville MI. I had a patio installed with a pop-up drain and also had my gutter's linked into it. Last winter I started getting leaking in my back room ceiling. This summer I had a roof guy do a bunch of work (install a sealant increase the flashing, etc). This winter same leaking/dripping in the back room ceiling. I have finally figured out (by all the icicles off my gutter) that my gutters have frozen up and the water off the roof is backing up beyond the flashing. The pop-up was covered in snow and frozen shut.
I came across this site while searching for a solution to this problem. I don't know if they put in gravel under the popup - that will be the first thing I check in the spring.