What to Do When Your Manhole Is Overflowing

There's nothing quite like opening the back door and finding raw sewage bubbling up from a manhole cover. It's unpleasant, it smells terrible, and it can feel like an emergency — because in many cases, it is.

Immediate Steps: Safety First

• Keep children and pets away — Sewage contains harmful bacteria including E. coli.
• Don't try to lift the manhole cover yourself — They're heavy and you don't want to lean over an open chamber of sewage.
• Stop using water in the house if possible — Every flush and tap run adds more to a backed-up system.
• Don't pour chemicals down the drain — They won't fix a blockage and just add to the overflow.
• Take photos — Useful for insurance claims or reporting to the water company.

What Causes a Manhole to Overflow?

Blockages

The most common cause. Fat, oil, grease, wet wipes, and sanitary products build up and restrict flow. For early warning signs, see our guide on signs of a blocked drain.

Heavy Rainfall

Combined sewer systems can be overwhelmed during heavy or prolonged rain, causing sewage to back up through manholes.

Collapsed or Damaged Pipes

A collapsed section restricts flow and causes backup. Often caused by ground movement, heavy traffic, or age.

Tree Root Ingress

Roots grow into pipe joints and gradually block the flow. It's slow but the overflow can seem sudden.

Fat, Oil and Grease Build-Up

Years of accumulated grease hardens inside pipes, gradually narrowing them until they block completely.

Who Should You Call?

• Public sewer (in the road or communal area) — Call your water company. They should attend free of charge.
• Private drain (within your boundary, serving only your property) — Call a drainage company like UK Drainage Services.
• Not sure? — Call your water company first. They'll either come out or tell you it's private.

Not sure about the difference? Our guide on who is responsible for blocked drains explains it all.

DIY vs Professional

An overflowing manhole is rarely a DIY job. The blockage is usually deep in the pipe, you need professional jetting equipment, and there may be a structural problem that clearing the blockage won't fix. If in doubt, call a professional. Read our guide on what to do when your drain is blocked for more advice.

How to Prevent Recurring Overflows

• Never pour fat, oil, or grease down the sink — let it cool and bin it.
• Only flush the three Ps — pee, poo, and (toilet) paper.
• Get a regular drain clean — periodic jetting keeps pipes clear.
• Trim trees near drain runs — manage growth or install a root barrier.
• Book a CCTV drain survey — find out if there's damage that needs repairing.

Need Help Right Now?

If your manhole is overflowing, call UK Drainage Services on 0333 577 4242. We offer emergency drain unblocking across the UK and can usually get an engineer to you the same day.