Ah okay, my bathtub drains all day now.
In February it started only draining once a day at like midnight, then it didn't drain at all for a few months and I had to bail it out, then it was midnight only again, now it's full time once more.
Got that?
…but what could that be?
The sewer line from my house to the main has been cracked by roots. Most of the year, it's above the water table, so when the bathtub drains some water flows out into the soil.
The non-draining parts are in the heart of the wet season, when the water table is above the pipe, and there's not pressure to drain.
And the "midnight only" parts? Well, midnight is when leaves open their pores for gas exchange, releasing oxygen and taking in carbon dioxide. They wait til then so they lose a minimum of water this way but they still lose a bunch, so to replace it the roots slurp up more water… which, if the soil water level is just a bit above the pipe, brings it briefly below, and the tub drains.
I was told about the pipe by my inspector when I moved in, I've held off until I'm further on planning the basement (/2nd floor) because I might want to get a bigger one put in for capacity with multiple units, interestingly last spring I had no tub problems but I had to keep plunging the toilet cause it didn't have enough suction for turds, but that hasn't been a thing this year.
Karafuto somehow gives me like +15 Woodcraft
Anyway an implication is you can obtain water in an area with trees but no aboveground sources by tying a plastic bag around the leafy ends of branches; when the pores open and water vapor escapes it’ll condense in the bags, which you can then retrieve.
Learned that one from the Scotsman on my last place’s couch, who had learned it in British Army survival training – the way he told it, a lot of their training was about handling being cut off behind enemy lines, which I guess makes sense.