What should I do if the tiles in the old bathroom leak down?

The only way, remove the tiles and redo the waterproofing!

The problem is serious.

Basically, it is caused by the upper floor residents' bathrooms. >>>More

Generally speaking, the water leakage in the upstairs bathroom is due to the fact that the floor waterproofing of the upstairs residents is not in place, so the water in the bathroom will leak downstairs; In general, after receiving the house, the owner is obliged to do a 24-hour waterproof test, that is, fill the waterproof place with water to see if the water leaks downward. >>>More

You'll have to go upstairs and check it out.

The leak on your roof doesn't necessarily correspond to the person upstairs, because you also said that the leaky seat is the wall of the bathroom upstairs. >>>More

If the leak point is in the floor drain range, it is difficult to solve the problem without knocking the tiles. However, the advantage is that you only need to knock off the tiles within the scope of the floor drain and re-do the waterproofing and then pave it, and you don't need to knock them all. >>>More