You’ve scrubbed the tiles. You’ve bleached every surface. You’ve sprayed enough air freshener to gas a small country.

And yet… that smell still lingers.

It’s not overpowering, just faint enough to annoy you every time you walk in. You start to wonder if you’re imagining it. Maybe it’s the drains? Maybe the grout? Maybe your house is just haunted by bad plumbing decisions from 1998.

The truth is, if your bathroom smells bad even when it’s clean, it’s not your cleaning skills, it’s your plumbing.

And once you know where that smell is really coming from, it’s surprisingly easy to fix.

1. Hidden Leaks: The Silent Stink-Maker

Not all leaks show themselves as puddles on the floor. Some hide behind walls, under tiles, or beneath your vanity, slowly rotting timber, growing mould, and releasing that damp, earthy smell that never quite goes away.

You can mop and spray all you want, but if water is sitting in hidden places, bacteria and mildew will keep coming back. Over time, that musty smell turns sour, and eventually, it starts to smell like something died in there.

What to look for:

• Peeling paint or bubbling walls near the shower or toilet.
• A damp smell that lingers no matter how much you clean.
• Warped skirting boards or soft patches underfoot.

If you notice any of these, it’s time to bring in a plumber. Finding hidden leaks isn’t a guessing game. Professionals use moisture sensors, thermal imaging, and experience to pinpoint exactly where the water’s sneaking out. Catching it early can save you thousands in structural repairs later.

2. Dry Traps: When Your Drain Loses Its Seal

Every drain in your home, including sinks, showers, toilets, and floor drains, has something called a trap. It’s that little U-shaped bend in the pipe that always holds a small amount of water. That water acts as a barrier, stopping sewer gases from coming back up into your bathroom.

If a trap dries out (which happens in showers or drains that don’t get used often), those gases have nothing to stop them. That’s when you get that unmistakable sewer smell creeping through the room.

It’s easy to assume the smell’s just from bad pipes, but what’s really happening is gas from the main line is slipping past a dry trap and escaping into your home. It’s unpleasant and can even be harmful to breathe over time.

How a plumber fixes it:

They’ll inspect your traps, refill any dry ones, and make sure your drains are properly sealed. Sometimes, a cracked or poorly fitted trap needs replacing entirely to stop the gases for good.

3. Vent Blockages: When Your Plumbing Can’t Breathe

Here’s something most people don’t realise. Your plumbing system needs to breathe.

That’s what your vent pipes do. They run up through your walls and out your roof to let fresh air in and sewer gases out. But when those vents get blocked by leaves, debris, or even birds’ nests, pressure builds up in the pipes and gases start pushing their way back into your bathroom.

That’s when you’ll start hearing gurgling from your sink or toilet or smelling something that shouldn’t be there.

Vent blockages are sneaky because you’ll never see them. You just smell the side effects. Clearing a blocked vent isn’t something you can do with a plunger or a bottle of cleaner. It often requires climbing onto the roof and using specialised tools.

This is where a plumber earns their keep. They can safely inspect and clear the vent, restoring airflow and ending that mystery smell once and for all.

4. Old or Failing Wax Seals Around the Toilet

If your bathroom smells like sewage and you’ve ruled out the drains, the problem might be sitting right under your nose, or rather, under your toilet.

Toilets are sealed to the floor with a ring of wax that stops gases and waste from leaking out. Over time, that wax ring can crack, shift, or simply break down. Once it does, air from the sewer system starts escaping into your bathroom every time you flush or sit down.

You’ll know it’s the culprit if the smell is strongest around the base of the toilet or if you notice the floor feels slightly soft or spongy nearby.

This isn’t a DIY job. Replacing a wax seal means removing the entire toilet, cleaning the flange, and reseating it properly. If it’s not done perfectly level, it’ll just start leaking again. Plumbers do this kind of job weekly, and it’s one of those fixes that’s far easier and cleaner when done by someone who knows what they’re doing.

5. The Build-Up You Can’t See

Even in bathrooms that are spotless, build-up happens inside the pipes. Soap scum, toothpaste, hair, and minerals from hard water combine to create a layer of grime that clings to the inside of the drain. Over time, bacteria grows on that layer and starts producing that lovely old drain odour.

You can pour all the store-bought cleaners you want down there, but most only mask the smell or clear the surface. The deeper bacteria will keep doing its thing.

Professional plumbers can perform a drain clean using safe, pressurised water jets that remove the buildup completely without damaging the pipes. It’s one of those behind-the-scenes jobs that make a huge difference and something every homeowner should consider every few years.

6. Broken or Damaged Sewer Lines

This is the big one and thankfully, the rarest.

If your bathroom smells truly awful and the stench spreads beyond that one room, you could be dealing with a cracked or damaged sewer line beneath the house. Tree roots, shifting soil, or simply age can cause pipes to crack and leak sewage gas under your floor.

Aside from the smell, you might also notice slow drains throughout the house, gurgling toilets, or even wet patches in the yard.

That’s not something any cleaner or air freshener can fix. It requires professional inspection, often with CCTV drain cameras, and potentially repairing or replacing part of the sewer line. The good news? Once it’s fixed, that nightmare smell disappears instantly.

Why Cleaning Won’t Cut It

Here’s the truth. A smelly bathroom doesn’t mean you’re dirty. It means something in your plumbing isn’t doing its job.

Air fresheners, candles, and extra scrubbing just hide the symptom. The smell always comes back because the underlying cause, whether a leak, blockage, or failing seal, is still there.

And that’s exactly why these problems need a licensed plumber, not another round of bleach.

Final Thoughts

Your bathroom should smell clean, fresh, and… invisible. No must, no sewage, no mystery odours.

If it doesn’t, something in your plumbing system isn’t working the way it should.

These problems rarely fix themselves, and the longer you leave them, the worse (and smellier) they get.

At Do Some Plumbing, we’re the go-to local plumbers in Logan, trusted by homeowners across Beenleigh, Shailer Park, Springwood, Underwood, and surrounding suburbs. We’ve seen every type of bathroom mystery you can imagine, from dried-out traps to broken seals and cracked pipes, and we know exactly how to find and fix the cause fast.

So if your bathroom still smells off even after a deep clean, it’s not your imagination, and it’s not your cleaning routine. It’s your plumbing asking for help.

Call the local plumbing experts at Do Some Plumbing, servicing Logan, Beenleigh, Springwood, Underwood, and beyond, for reliable, honest plumbing that actually solves the problem.