Treat it as contaminated

Sewage can contain harmful microorganisms. Keep people and pets away from affected rooms and avoid unnecessary contact. If electrical equipment is affected, stay clear until it has been made safe.

What may be happening

During heavy rainfall a combined sewer can surcharge, pushing wastewater back towards lower connections. A private blockage can produce similar symptoms. Distinguishing between them is important.

Call the right organisation

Contact your water company about suspected public sewer flooding. If only your private drainage is affected, a drainage specialist may need to investigate. If there is an immediate health or safety threat, follow emergency advice.

Do not install a valve without advice

A non-return valve can help in some situations, but an unsuitable valve can block the property’s own wastewater discharge during an event. The design and maintenance arrangement matter.

Evidence for insurance

Take photographs safely, note when the water appeared and contact your insurer before disposal or major remedial work. Keep a record of who you spoke to.

After the water goes

Contaminated items may need specialist handling. Agree a cleaning, drying and reinstatement plan with your insurer or a suitably experienced contractor.

Assume wastewater may be hazardous

Sewage backing up through a toilet, shower or floor drain can expose the household to harmful microorganisms and damaged electrical equipment. Keep people and pets out of the affected space and avoid using fixtures that may feed the surcharged drain. Do not investigate by climbing into a manhole or putting hands into wastewater. Report the problem promptly to the relevant sewerage provider or drainage professional, depending on which pipe is responsible.

Find out who owns the failed section

If neighbouring homes are also affected, the fault may lie in a shared sewer rather than a private branch. A drainage contractor can assess private pipework, but the water company may be responsible for public sewers and certain shared pipes. Photograph the incident, record whether rainfall coincided and ask for written findings before paying for major excavation. Once the wastewater is removed, contamination and hidden moisture may require specialist cleaning and monitored drying.

Who to contact and what to tell them

If wastewater has entered the home, do not use affected toilets, showers or other appliances until the drainage situation has been assessed. Keep children and pets away from the contaminated area, and avoid contact with the water. If you can do so without going into danger, note which fittings overflowed, whether neighbours have similar problems and whether it coincided with heavy rain. Report suspected public sewer flooding to the water and sewerage company. For a private blockage, a competent drainage contractor may be needed.

Give the insurer prompt notice if there is likely to be damage. Photograph the affected rooms from a safe place and record the time and approximate depth, but do not handle contaminated possessions unnecessarily. If you are in rented accommodation, tell your landlord or managing agent straight away as well.

Cleaning and preventing a recurrence

Floodwater contaminated with sewage can affect floor coverings, insulation, cupboards and hidden spaces beneath a suspended floor. An ordinary household clean may not be sufficient. A suitable recovery plan should deal with removal of contaminated material, cleaning, drying and confirmation that the building is safe before reinstatement. Electrical equipment exposed to floodwater must be assessed by a competent person; do not switch it back on as an experiment.

Preventative equipment such as a non-return valve needs careful specification. It can limit backflow in some arrangements, but it may also prevent your own wastewater from discharging while closed. The pipe layout, maintenance access and other possible entry routes must be understood first. Ask for a drainage investigation that explains why the overflow happened, rather than purchasing a device solely because it has been advertised as flood protection.

Keep a clear record of recurring incidents

If the same wastewater problem has occurred before, keep the dates, rainfall conditions, reported reference numbers and any drain survey findings together. This helps a water company or private contractor distinguish an isolated blockage from a repeated capacity or structural problem. It also makes an insurance discussion less dependent on memory. Ask the investigating organisation to confirm in writing whether the problem is thought to be in a public sewer or private pipework, and what further action is proposed.

Reliable further information

For current warnings, official flood-risk maps and safety advice, use the relevant government service. This website cannot assess live conditions at your home.

Government flood guidance · National Flood Forum · Citizens Advice