@quill-of-thoth – There’s actually no drain to handle rain runoff back there at all, as handy as it might be sometimes. But, I’m definitely glad it’s just rainwater and not also backed-up kitchen drains now👍 That metal cover the water was coming up from is just an inspection cover for the house drains. The pavement slopes away from it, especially into that one corner.
Worst case, now I know you can take the lid off and sweep water into the hole if necessary! Never actually had any reason to open it before the water company guy came and had to poke around in there. The standing rain should eventually soak into the ground through the pavement cracks, though.
The patio setup in general seems like just another in the collection of DIY Don’ts from some previous owner. Planning for drainage? Using one of those fancy levels? Who has time for such nonsense?! 🙄