Sewage backed up into the house. This is the one you do not clean yourself.

Drying removes water. It does not remove what was dissolved in it. Carpet, underlay, drywall below the water line and upholstered furniture absorb contaminated water into a structure that cannot be cleaned through, so the industry standard for water damage restoration treats them as waste rather than as items to dry.

Hard, non-porous surfaces are a different matter: tile, sealed concrete and finished timber can be cleaned and disinfected. The dividing line is whether the material can be cleaned all the way through, not how bad it looks.

This is also why a backup costs more than a clean-water flood of the same size. The volume of water may be small and the volume of skip may be large.

Every flush, every sink and every washing machine cycle upstream of a blockage pushes more water toward the same failure. Until someone has established where the blockage is, stop using water in the building entirely — including appliances on a timer, which is the one people forget.

If the backup happened during heavy rain and several neighbours have the same problem, the blockage is probably not in your lateral, and the water authority needs to know rather than a plumber.

A homeowners policy normally excludes water that backs up through sewers or drains unless a specific endorsement was bought. It is a cheap add-on that most people do not know they declined, and it is worth checking your Declarations page today rather than at the point of claim.

Where a municipal sewer caused the backup, there may be a claim against the authority as well — those have their own notice deadlines, often short, and they run from the date of the incident.

Flood cover is again separate: if storm water entered the system and came up through your drains, whether that is flood or backup is a question your policy answers rather than common sense.