You must first report the seepage problem to the manager and/or the incorporated owners of your building.
You should report the seepage problem to the Joint Office of "Buildings Department" and "Food and Environmental Hygiene Department" at its telephone number 1823.
The Joint Office has legal power to identify the source of seepage posing a health nuisance; and to issue a wrongdoer a Nuisance Notice requiring the abatement of nuisance; and to prosecute the wrongdoer. Upon conviction, the penalty will be a maximum fine of $25,000 and a daily fine of $450.
Nevertheless, to claim damage, loss and/or apply for injunctive remedy, you are advised to immediately consult your lawyers, and lodge a civil claim against a wrongdoer(s). For e.g. the wrongdoer could be an owner of an upper flat (with defective pipes) and/or a building manager (who failed to repair defective pipes and/or external walls in the common area of the building.