Didn't even know that a hot water recirculator was a thing, and with how old the house is, I'm betting not.

They seem to be fine. They were a bit low, but I just swapped the sed filter and it fixed the two sinks being a bit low, but didn't do much for the shower.

There's a cartridge in the mixer? Is this something I can swap easily? The previous idiots who owned my house did all copper straight to the mixer, didn't attach it to anything behind the wall. So the only thing holding it where it needs to be is the bolts from the actual handle. Pain in the ass.

This is supposed to be spooky but all I can think of is it's 2 a.m and a roommate coming in going..."I made waffles!" lol