This may seem like a petty or stupid question, but it’s actually perplexing me.
I have a bath/shower combo unit. Sometimes when I take long showers, if I don’t seal the shower curtain perfectly, a little bit of water will pool around the tub. No big deal, I’ll wipe it up with a towel and move on. The tub area clearly must slightly lower than the rest of the bathroom by a small margin even if it’s not obvious, because the water is always right up against the tub. Often I even leave my dirty clothes on the floor on the other side of the bathroom until I throw them in the washer, and they never get wet, because the water never spreads around the floor.
Today I took a long shower, I was a little careless with the shower curtain… and the water spread all around my bathroom. Some socks I left on the opposite side of the bathroom got soaked. Water was evenly scattered around the bathroom floor. Which has never happened before. The amount of water didn’t seem any larger than usual, so I don’t think that’s the reason it spread around.
So, explanations: the area around the bathtub spontaneously lifted up, causing the floor to be level. The rest of the floor in the bathroom lowered itself, causing it to be level. The geography of the Earth has changed and I’m about to get swallowed up into a sinkhole. Some sort of age related settling or other factor in the building caused floors to tilt slightly in a different way.
My WAGs
1)Your house settled a bit and where it used puddle is now higher.
2)There was, in fact, more water on the floor than usual.
3)Whatever coating is on the floor, be it wax or some type of polish kept the water pooled in one area due to surface tension. If that finish wore off, or if the water that splashed out this time had soap in it, it could have broken the surface tension and allowed it to spread.
I think you’d have to wait for it to happen a few more times to decide if it was just a one time thing or if something actually changed.
I thought that perhaps it was a lot of water - and so the local “basin” of the water near the tub was full and so the water started pushing outwards. But there wasn’t an abnormally large amount of water outside the tub - it seemed like the same fairly even shallow layer of water around the rest of the bathroom. Also, it’s an apartment building, if that has any relevance. The bathtub is against the wall of another apartment and not the edge of the building. I’m not sure how that may play into whether or not something settled.
The subflooring may have shifted due to getting wet all those times. The classic is fiberboard which swells when it gets wet (and therefore shouldn’t be used in such applications but …). So the part that’s been getting wet is now higher and the water is going elsewhere.
Make sure that you don’t have mineral deposits in your shower head that are directing a very small stream of water up and over the curtain. It’s happened to me before.
Also, regardless of what the actual reason is, if you’re getting enough water outside the tub that you notice a difference in how it pools, you should probably redo the caulk. Or, at least buy something to keep the curtain up against the wall or block the water from getting out. There’s a bunch of different options to do that, all cheap and all a lot less work than dealing with water damage.