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Doing a load in your washing machine only to be hit by a rotten egg smell when you open the washer door is more than just disheartening—it’s downright off-putting. You expect the scent of clean laundry, not the stench of something that smells like it crawled out of a sewer.
While it might be tempting to blame the detergent or the last load of socks, the truth is that these smells often point to deeper plumbing or maintenance issues.
That bad smell isn’t just unpleasant—it can signal the presence of sewer gas, a clogged vent pipe, or even a natural gas leak (though that last one is much less common, it’s still worth ruling out). In some cases, it’s a matter of build-up in the drain line, trapped moisture in seals, or poor drainage left unchecked for too long.
The good news? Most of these problems have straightforward solutions you can tackle yourself, before calling in a professional plumber. In this guide, we’ll unpack the most common causes behind the smell coming from the laundry drain, show you how to fix them, and share tips to prevent it from coming back. With a few simple changes, you’ll have your laundry room smelling fresh again in no time.
Behind every smoothly running washing machine is a drainage setup that quietly does the dirty work. At the heart of this system is the drain pipe (or drain line) and the all-important P-trap, sometimes called a drain trap or a U-shaped pipe. Its job? To hold a small amount of water that acts as a barrier, preventing sewer gas smell and other unpleasant smells from rising back up into your home.
But when that P trap dries out, becomes blocked, or isn’t properly installed, that barrier disappears—and with it, your protection from those foul odours. Add a clogged drain line or a faulty vent pipe, and you’ve got a recipe for a smelly disaster in your laundry room.
Understanding how these components work together is the first step to identifying and fixing the source of the stink.
If your laundry is rarely used, the P trap can dry out, losing its seal. That opens the door for a sewer smell. Fix? Pour about a gallon of hot water down the floor drain once a month. Keeps the trap filled and the air fresh.
A vent pipe helps regulate pressure and lets sewer gases escape outdoors. When it’s clogged, those gases back up into your laundry room, turning it into a smelly steam room. You might smell raw sewage or sewage gas, especially with a partial clogged vent pipe or improper venting.
The solution: call a professional plumber or carefully clear the blockage—especially if it’s bird nests or debris.
Lint, hair, soap scum and fabric softener cling to the walls of the drain hose and washing machine drain. Over time, they rot and cause that unmistakable sewage smell. Especially in a front-load washer or top-load washer, neglected appliances suffer from this. Running a deep cleaning cycle monthly helps eliminate this.
Many front load washing machines include a little trap called a drain pump filter, designed to catch bits of lint, coins, nails. If it’s not cleaned regularly, it becomes a breeding ground for bacteria and brings that rotten egg and sulfur like smell right to your laundry room. Clean it thoroughly every couple of months.
A leaky pipes or hose dribble dampness around the P trap or under the washer. That unseen moisture invites mould, mildew, and smell. Even a small drip from washing machine hoses can stay hidden until the stink gets powerful. Inspect hoses and joints regularly.
If the smell is particularly strong—think raw sewage—you may have a cracked sewer line under the house or a compromised sewer gas seal. That’s serious and calls for a professional plumber to inspect and repair.
Don’t ignore a natural gas or natural gas leak suspicion either: those smells differ (more chemical), but always play it safe.
When the washing machine drains, it may push build‑up or water sludge from the drain line into the living space if the vent pipe is blocked or the P-trap is empty. That kicks sewer gas upward.
Plus, if the washing spin pumps out wet clothes with detergent residue, the resulting odour can linger—especially around the rubber door boot or rubber seal, common spots in front load washer setups.
Mix half a cup of baking soda with some hot water (or a splash of vinegar if you prefer) and slowly pour it down the drain. Let the mixture sit for 15 to 30 minutes to break down grime and gunk, then flush it through with more hot water.
Doing this once a month can help keep the build-up at bay and reduce the risk of a clogged drain. Just remember that while it’s great for clearing minor blockages and odours, it won’t fix issues like a clogged vent pipe or a dried-out P-trap.
If you suspect a clogged drain line, a drain snake can be a handy tool to have on hand. Gently feed it into the drain and twist as you go to help break up any trapped lint, hair, or clumps of soap scum. If you hit resistance or pull out a wad of gunk, you’ve likely found the culprit.
Once cleared, flush the drain pipe with plenty of hot water, then run your washing machine on an empty cycle to rinse everything through and check that the water flows freely.
For a front-load washing machine, open the washer door, access the drain pump filter (typically at the base), place a bowl beneath, unscrew, clean debris, rinse, and replace. Wipe out the rubber seal or rubber door boot—it traps moisture and grime. Finally, run a maintenance cycle with good washing machine cleaner or hot water and about a gallon of vinegar/baking soda blend.
If you suspect a clogged vent pipe (common if your laundry room is downwind of the roof vent), call a professional plumber. They’ll often go onto the roof and rod/jet the vent pipe clear. Proper vent pipe function is crucial for keeping sewer gas outdoors.
Seek help when:
A professional plumber can CCTV inspect the drain line, reseal or replace defective sections, fix the drainage system, and ensure everything is properly installed with proper venting.
A smell coming from the laundry drain can range from minor skincare from soap scum, to serious sewer gas smell or even the rare natural gas leak. Most fixes are simple: rehydrate your P-trap, clear blockages with hot water, baking soda, enzyme cleaners or a drain snake, and keep washing machine seals and drain pump filter clean. But if the stench persists, especially a strong rotten egg smell or actual sewage smell, don’t wait—engage a professional plumber.
Once everything is cleared, freshened, and ventilated, your laundry room smelling fresh again is completely achievable. Time to put an end to the stink and get back to clean laundry days!
If you need a plumber on the Gold Coast to assist with your blocked laundry drain, speak with our team at Gold Coast Plumbing Company today for fast and effective service!
Start with hot water and baking soda, clean the drain pump filter, ensure your P-trap has water, and run cleaning cycles. If odour persists, check under the washer and call a professional plumber for vent or sewer-line issues.
It usually means the drain line or P-trap is blocked or dried out, or the vent pipe is clogged, letting sewer gas back up. Proper routine cleaning and professional checks solve most issues.
