Discovering raw sewage backing up into your home at 11pm is one of the most distressing things that can happen to a London homeowner or tenant. The instinct is to panic, but sewage emergencies follow a predictable pattern and responding methodically in the first 30 minutes significantly limits the damage — to your property, your health, and your stress levels. This is the exact plan we advise callers to follow while we're on the way.
Immediate Priority: Stop Using Water
The first thing to do when sewage backs up into a drain, toilet, bath, or floor gully is to stop all water use in the property immediately. Every litre of water discharged — toilet flush, tap, washing machine — pushes more sewage backward through the blocked pipe and into your home.
- Do immediately:
- Turn off all taps
- Do not flush any toilets
- If a washing machine or dishwasher is running, cancel the cycle
- Do not run the shower or bath
This single step limits how much sewage enters the building while you work through the rest of the plan.
Identify the Scope: One Drain or All Drains?
The scope of the blockage determines both the urgency and the responsibility. Test this quickly and safely:
If one drain is backing up (e.g., the kitchen sink, but the bathroom is fine): this is likely a localised blockage in the branch pipe serving that fixture. Less urgent, but still needs attention tonight if sewage is visible.
If multiple drains are backing up simultaneously (toilets, baths, sinks, floor gullies): this indicates a blockage in the main soil stack or the lateral drain leaving the property. This is the more serious scenario and the one that causes sewage to back up across multiple rooms.
If neighbours are also affected: the blockage may be in the public sewer. In this case, the emergency responsibility shifts to Thames Water. Call their 24-hour emergency line (0800 316 9800) as well as a private drainage contractor. For context on who is responsible for what, our post on blocked drain vs blocked sewer responsibility explains the boundary in detail.
Health and Safety: Sewage Is a Biohazard
Raw sewage contains pathogenic bacteria including E. coli, Salmonella, and Campylobacter, as well as viruses and parasites. In a confined space, it also produces hydrogen sulphide gas, which has a characteristic "rotten egg" smell and is toxic at elevated concentrations.
- Do:
- Open windows to ventilate the affected space
- Keep children and pets out of the contaminated area
- Wear rubber gloves and avoid touching your face if you need to access the area
- If the smell is overwhelming and you feel unwell, leave the space and ventilate before re-entering
- Don't:
- Use bleach or cleaning products on the sewage backup before it has been cleared — this doesn't neutralise the contamination and may generate harmful fumes
- Try to manually clear a toilet that has raw sewage backing up through it
- Allow the contaminated water to contact any food preparation surfaces
Check the External Inspection Chamber
If you have an external inspection chamber (manhole) accessible in your garden, rear courtyard, or on the street side of your boundary, check it. This requires a torch and ideally a screwdriver or flat bar to lift the cover.
Chamber is full or overflowing: the blockage is downstream of this chamber — in the lateral drain leaving your property, or in the public sewer. Call Thames Water immediately alongside your private drainage contractor.
Chamber is empty: the blockage is upstream of this chamber — within the property or in the drain leading to it. This is a private blockage, and our emergency drain service covers this.
Chamber has normal flow: the blockage is in a branch pipe before it joins the main drain. The scope is more limited.
Call a Sewage Emergency Engineer in London
Once you've done the above steps — stopped water use, identified the approximate scope, ensured the space is safe — call an emergency drainage contractor. In London, you should expect a response within 60–90 minutes for a genuine sewage backup emergency, not a four-hour wait.
- When you call, tell the operator:
- Whether one drain or multiple drains are affected
- Whether the external chamber is full, empty, or has normal flow
- Whether neighbours are affected
- The property type (house, flat, basement flat — particularly relevant for access)
This allows the contractor to bring the right equipment for your situation.
Our emergency drain service in London operates 24 hours a day, 7 days a week. Request a quote online via our contact form.
While You Wait
While the drainage contractor is on the way:
Document the damage. Take photographs of the affected areas, the level of backup, and any visible damage to flooring or skirting boards. This is important for insurance claims.
Notify your insurer. Home buildings insurance and contents insurance both potentially cover sewage damage. Call the emergency claims line on your policy — they may dispatch a loss adjuster or approve emergency remediation work. Do not begin deep cleaning before the insurer has recorded the damage.
Notify your landlord if you're a tenant. Sewage emergencies are the landlord's responsibility to resolve. Call immediately, even at night — this is what emergency contact clauses in tenancy agreements are for.
After the Emergency Is Cleared
Once the blockage has been cleared and the sewage backup has stopped:
Disinfection. Any surfaces, flooring, or fixtures contaminated with sewage must be disinfected. Use a product labelled as effective against bacteria and viruses, allow adequate contact time, and ventilate during and after. Soft furnishings, carpets, and materials that cannot be fully disinfected should be treated as contaminated waste.
CCTV survey. A sewage emergency is almost always caused by an underlying drain problem — a collapse, a severe root intrusion, a blocked sewer. Clearing the immediate blockage doesn't fix the cause. Arrange a CCTV drain survey within a few days to identify and address the root cause and prevent a recurrence.
Review your drainage maintenance. If this is not the first sewage backup the property has experienced, a planned maintenance programme — including periodic jetting — is worth considering.
Building an Insurance File the Loss Adjuster Will Accept
Sewage damage claims in London are routinely under-paid because homeowners don't realise the level of evidence loss adjusters expect. Most major UK home insurers — Aviva, Direct Line, Admiral, LV — treat sewage backup as a specific peril under buildings cover, but the burden of proof sits firmly with the policyholder. The hour after the engineer leaves is when you build the file that determines how much you recover.
Photograph in layers. Wide shots establishing each affected room, mid-distance shots of damaged items grouped together, and close-ups showing the contamination line on skirting boards, doors, and walls. Time-stamp the camera before you start — most phones do this automatically but check. London adjusters frequently ask for "tide marks" on plaster as proof of standing water depth, and a single close-up of a stained skirting can swing a claim by several thousand pounds.
Save the engineer's report. Our sewage emergency callouts produce a written job sheet stating the cause of the blockage, location (private drain vs. lateral drain vs. public sewer), the equipment used, and any onward recommendations. This document is the single most important piece of evidence for an insurer — it confirms the cause was a drainage failure rather than something excluded under your policy (e.g., gradual deterioration, a maintenance issue you ignored).
Log everything by hour. A simple notebook or notes app entry showing when you discovered the backup, when you stopped using water, when you called Thames Water, when the engineer arrived, when the property was made safe. This timeline matters for "loss mitigation" — insurers reduce payouts when they suspect avoidable delay.
Get three written quotes for remediation. Loss adjusters expect competing quotes for any significant remediation work. Approved restoration contractors familiar with London sewage damage will provide quotes that itemise contamination removal, antimicrobial treatment, and reinstatement separately. Our drain cleaning cost guide explains what a private clearance element of this work typically costs.
FAQ
Is a sewage backup always a drainage blockage?
Usually, yes. Occasionally a sewage backup results from a collapsed pipe rather than a blockage — the drainage has nowhere to go and backs up into the nearest low point. A CCTV survey after the emergency will distinguish between the two.
Who pays for clearing a sewage emergency in a rented property?
The landlord is responsible for maintaining drainage in a rented property and must pay for emergency drainage repairs. If the landlord is unreachable, a tenant can commission emergency works and claim reimbursement — keep all receipts and documentation.
Can Thames Water charge me for the emergency?
If the blockage is in your private drain, Thames Water will not respond and will not charge — it's outside their jurisdiction. If the blockage is in the public sewer, Thames Water responds for free. The boundary is your property's external wall in most cases — our post on drain vs sewer responsibility explains this.
How long does sewage contamination remain hazardous?
Pathogenic bacteria in sewage can survive on surfaces for days to weeks, depending on temperature and surface type. Full disinfection rather than just cleaning is essential. If in doubt, a professional deep cleaning service with specialist contamination equipment is the safest approach.
What does a 24-hour emergency drain callout cost in London?
The cost of an out-of-hours emergency response depends on the nature and severity of the blockage. Our drain unblocking pricing page has more detail.
