Every time I have seen a spider at home, in the bathroom, whether it was in a house or in apartments, whether on the bottom or upper floor, I always immediately assumed that it had come "through the pipes"; that is, crawled up through the drain pipe leading into the bathtub, or the drain hole in the floor which takes care of any water that spills out on the floor.
Or even that it had swimmed all the way up through the water toilet.
Luckily, it hasn't happened for quite some time now (knock on wood...), but this thought was especially present in my mind when the spider was sighted in the actual bathtub.
My question is: do spiders actually crawl up such pipes, into homes? Or is this a false assumption? Don't spiders tend to come in from opened doors and windows? Not through pipes?
I mean, it's not like the drain pipes lead directly down underground with dirt and creatures living there. It's still connected to the bigger sewage pipes, no? I cannot imagine any creature surviving not only the oxygen-less, long trip through these large sewage/water pipes, but to also have the strength to stop and actively push themselves up and keep crawling all the way up to my apartment/house's bathroom.
But maybe I underestimate those vile creatures of pure evil.
On the other hand, it seems unlikely that a spider would come from the outside, though a window or door, only to find itself crawling into the bathttub and be sighted there, so that talks against my theory that it's impossible for insects to enter through these drain pipes...