Who cares if the drain pipe of the washbasin leaks downstairs?

If it is not the main drainage pipe itself, or the drainage pipe wall is not waterproof at that time, resulting in water leakage, if it is the first case, it can be coordinated with the property, not all the landlord's problems; If it is the second case, it is really the landlord's problem. You should take the initiative to help the downstairs coordinate and solve it, otherwise the neighbors will lose popularity if they can't do it.