Are the droplets falling from the bathroom ceiling due to water leakage from a neighbor's bathroom, which touch the body and clothes, ritually impure, necessitating changing clothes and washing the body upon contact?

The basic principle concerning things is purity, and one does not deviate from this principle except with certainty. Therefore, gutter water is judged to be pure, even if its impurity is suspected, as long as that impurity is not certain. If a person ascertains that what has touched him is actual impurity (such as urine), then he must purify it.