Keep clear of hazards first
Keep people away from a sagging or bulging ceiling and from water near electrical fittings. Do not touch wet switches, fittings or appliances. Where there is immediate danger, use the appropriate emergency service. Do not wait for a website enquiry to be answered.
Limit the leak only where safe
If you know the water isolation point and can reach and operate it safely, turning off the affected supply may help limit damage. Do not force an unfamiliar valve or enter an unsafe area. Seek professional help when you are unsure.
Record the timing rather than guessing the source
If safe, note whether water appeared during showering, heating use or rainfall. Photographs can help show how a stain changes. Water can travel through a void, so the fitting directly above the stain is not necessarily responsible.
Arrange access above and below
In a flat, contact the landlord, occupier or managing agent to arrange access to the relevant spaces. Shared risers and communal valves may also need permission. A plumbing investigation is appropriate for a suspected pipe or fitting issue; roof and building defects may need a different specialist.
What to tell us when you enquire
Arrange authorised access above the damage where possible. Keep people clear of a bulging or damaged ceiling and do not open it yourself just to help the investigation.
Related reading
Help with this problem
Ceiling leak detection
Work back from water damage overhead to a likely plumbing source.