Sewer smell in the house or yard: causes and what to do

First: is it sewer, or gas?

Sewer smells are earthy and like rotten eggs, and they’re usually strongest near a drain, toilet or floor waste. If the smell is near a gas appliance, the meter or the cooktop, treat it as a gas leak: don’t use switches or flames, open doors and windows, leave the house, and call Triple Zero (000) or your gas distributor’s emergency line from outside. Gas work needs a licensed gasfitter.

What a sewer smell usually means — most likely first

1. A dry trap or floor waste. Every fixture holds a little water in its trap to stop sewer air coming back in. A spare shower, laundry trough or floor waste that rarely gets used can dry out and let the smell straight through.
2. A failed toilet seal. The connection between the toilet pan and the drain can perish or crack over time. A smell around the base of the toilet, sometimes with a slow leak, points here. On older homes the original cast-iron connection under the toilet can perish, and the fix is replacing it with new PVC.
3. A venting problem. Drains need air. A blocked or poorly fitted vent can pull water out of traps, so the smell comes and goes, often with gurgling.
4. A partial blockage. Waste sitting in a slow drain smells. If drains are also slow or gurgling, or the outside gully is full, a blockage is likely.
5. A cracked or broken drain. A damaged pipe under the house or in the yard can let sewer air and moisture into the ground. Smells under the floor or in one spot in the yard, sometimes with damp ground, point here.

What you can safely check yourself

• Top up every floor waste and rarely used fixture with a bucket of water, then wait a day. If the smell goes, a dry trap was the cause.
• Check around the base of each toilet for movement, damp or staining. A rocking pan or damp floor is worth reporting when you call.
• Run the fixtures and listen. Gurgling or slow draining alongside the smell points to a blockage or venting fault.
• Look at the outside gully. Make sure it’s not covered by garden or pavers, and check whether water is sitting in it.
• Note when it’s worst — after a shower, in hot weather, when it rains, or all the time. It helps narrow down the cause.

What not to do

• Don’t just mask it with air fresheners or bleach. If it’s a seal or a broken pipe, the smell will keep coming back.
• Don’t seal over a floor waste or the outside gully to stop the smell. They’re there to let an overflow out safely.
• Don’t pour chemical drain cleaners in. They won’t fix a seal, vent or broken pipe, and they’re a safety risk.

When it’s time to call a plumber

• The smell is still there after topping up the floor wastes
• There’s damp, staining or movement around the toilet
• Drains are slow or gurgling as well
• The smell is under the floor or in one spot in the yard
• The outside gully is full or overflowing — stop using water and ring us

How Zebra finds and fixes it

Start with the simple things. We check the traps, floor wastes, toilet seals and vents first, because that’s where most smells start, and the fix is usually small.

Camera when the source isn’t obvious. If the fixtures check out, the CCTV camera goes down the line while you watch the screen with the plumber, and the pipe locator marks where a crack, break or blockage sits.

One fixed price, approved before any work starts. We quote one fixed price for the fix and nothing starts until you approve it. The quote is obligation-free.

Our workmanship is backed by a lifetime labour warranty. If the smell comes with gurgling, our gurgling drains guide has more.

Whose drain is it?

Everything on your side of the connection point is yours to maintain: the pipes under the house and yard, the overflow relief gully, and — in older suburbs — the boundary trap. Your water corporation (Yarra Valley Water, South East Water or Greater Western Water, depending on where you live) owns the sewer main itself, and the council owns the street's stormwater drains. Older and subdivided blocks sometimes share one combined drain across several properties, and a fault in the shared section is usually a shared cost. We camera and locate the fault first, so you know exactly whose side it sits on before anything is quoted — and if it turns out to be on the corporation's side, we'll say so and point you to their faults line rather than charge you for someone else's pipe. One tip worth acting on today: keep your overflow relief gully (the grated drain outside, usually near a side or rear wall) clear and uncovered. It's designed to spill outside instead of through your bathroom floor, and insurers can take a dim view of a blocked or built-over gully after a sewage spill.

Common questions

More plain-English help in our drain guides.