Will my bathtub fall through the ceiling?

The longer you wait on a repair like this, the more it will cost. Get it fixed right away.
The bath probably won’t fall thru the floor, but it will cause a lot of problems from dry rot to mold.

Well, if you’re that concerned, then you definitely don’t want to be taking baths. At least with a shower the only added weight is you and whatever water is flowing into the tub and down the drain. When you take a bath, then you add the weight of hundreds of pounds of water, plus your weight whenever you’re in the tub and touching the bottom of the tub.

If you have that much water in the ceiling, then you may as well use that broom to break out the ceiling entirely where it’s waterlogged (it’s going to come out anyway) and shine a light in there to see how badly rotted the floor joists are. If they’re blackened and soft with rot, then you should consider staying out of the upstairs bathroom… and out of the room beneath… until you get it all repaired.

Minor leaks are one thing; they’ll deface the ceiling and eventually cause a problem. “A ceiling full of water” is already a huge problem; you just don’t know yet how huge.

By the way, if there’s any “springy” feeling to the upstairs bathroom floor, then don’t try any of what I suggested – it’s already too late for you to even test or examine.

Take a bath. A leak will take years to rot through the main joists, the water is only leaking through the floorboards.
But get it fixed soon or it will cost more.
This is what is underneath your floorboards, it wont rot or give way in a hurry, gosh they even make boats out of that stuff. Take a bath smelly ;)

@Odysseus you’re absolutely right about what’s there in terms of floor joists, but neither of us knows how many years and years this rot has already been allowed to occur. So I still urge caution until that is known. More than likely you’re right, and it’s a newly broken drain trap or loose / broken joint in the water supply lines, and not a structural failure yet. (In fact, you probably are right, because the downstairs ceiling would have caved in years ago and the room – the whole downstairs, for that matter – would be foul with mold, moss and decay. But still… I don’t know.)

The key is knowing when the leak started. Has this been something that has been very small and has grown slowly over years? Or is it something that just started, and got bad quite quickly. If it is the former. you probably don’t want to be taking a bath. Wood takes a while to rot, but several years could significantly weaken it.

If it is a sudden leak, then something has failed. I assume you would mention it if it was on the floor of the bathroom, so it is probably not something in the bathroom, unless you have some pipes hidden in the walls. Anyway, joints can fail and even pipes can fail fairly catastrophically. On the other hand, you don’t really say how much water is coming down.

If the leak is in the ceiling, then you’ll probably have to dig up the floor in the bathroom to get at it. I would start getting estimates for the job now.

Have you tried putting your weight on the floor of the bathroom to see how sturdy it is? You kind of press down in an almost hopping motion. If you have no movement, you do it harder. If there is movement, you probably should test how much there is, to get a sense of how far things have gone.

I seriously doubt your tub is going to crash through to the floor below. If it starts happening, you’ll feel it and be able to get to safety long before it actually falls through. My guess is that it will be fairly safe to take a bath. Probably the situation will help you save water, as you’ll use less water in the tub and take a shorter bath. Just in case.

On the other hand, I wouldn’t want to run more water through my pipes than I absolutely have to. I certainly would be leery of it if it were the waste pipe that was compromised. Bath water is bad enough to come down, but the waste from the toilet? Not interested. But probably the leak is on the supply side. Good luck!

How long has it been leaking?