I Have A Sewer Smell In My House, Why? There are few things more off-putting than a persistent “rotten egg” or sewage smell inside your home. It’s embarrassing when guests visit, but more importantly, it can be a health hazard.

Sewer gas contains methane and hydrogen sulphide, which aren’t just smelly, they can be toxic in high concentrations. At Mr24HourPlumber, we’ve sniffed out and fixed hundreds of these issues.

Here is why your house might smell like a drain and how to stop it.

1. The “Dry P-Trap” (The Quickest Fix)

Every sink, shower, and toilet in your home has a U-shaped pipe underneath it called a P-trap. This curve is designed to hold a small amount of standing water, which acts as a seal to block sewer gases from rising up into your room.

The Cause: If you have a guest bathroom or an en-suite that hasn’t been used in weeks, the water in that trap can simply evaporate.

The Fix: Run the taps for 60 seconds and flush the toilets in every room of the house. This refills the traps and restores the airtight seal.

2. A Faulty “AAV” (Durgo Valve)

Many modern UK homes use an Air Admittance Valve (AAV), often called a Durgo valve. These are one-way valves usually found under the sink or in the loft that allow air into the pipes to help drainage but stop smells from coming out.

The Cause: Over time, the rubber seal inside the valve can perish or get stuck in the “open” position.

The Fix: These are inexpensive and easy for a plumber to replace. If the smell is strongest under the kitchen sink or in a utility cupboard, this is your likely culprit.

3. Damaged or Perished Toilet Seals

At the base of your toilet, where it connects to the soil pipe, there is a wax or rubber ring.

The Cause: If the toilet is slightly loose and “rocks” when you sit on it, that seal can break. Even a tiny gap allows sewer gas to seep into the bathroom.

The Fix: The toilet needs to be removed, the seal replaced, and the unit properly secured to the floor.

4. Blocked Soil Vent Pipe (SVP)

Your plumbing system has a “stack” or vent pipe that usually exits through your roof. This allows sewer gases to vent safely into the atmosphere.

The Cause: Birds’ nests, leaves, or even a dead squirrel can block this vent. When the gas can’t go up and out of the roof, it gets pushed back down into your home.

The Fix: This requires a professional with the right ladders and clearing equipment to inspect the roof-level vent.

5. Cracked Underground Drains

If the smell is strongest on the ground floor or in the cellar, the problem might be structural.

The Cause: An old clay pipe may have cracked due to tree root ingress or ground movement, allowing raw sewage to leak into the soil beneath your floorboards.

The Fix: We use CCTV drain surveys to look inside the pipes without digging up your floor. This identifies exactly where the break is so we can fix it with minimal disruption.

Don’t Just Mask the Smell, Fix the Source

Scented candles and air fresheners are only a temporary fix for a structural plumbing issue. If the “refilling the traps” trick didn’t work, it’s time to call in the experts.