Why Does My House Smell of Drains? Causes and Fixes

A drain smell in the house is one of those problems you can't ignore. It's worse in winter, when the windows are shut and the heating's on. And it has a habit of coming and going, which makes it hard to pin down.

The good news is that most drain smells have a simple cause. Some you can fix yourself in a few minutes. Others need a professional to find.

Here are the eight causes we come across most often, starting with the easy ones.

1. A dried-out trap

Every sink, bath, shower and toilet has a U-bend or trap under it. It holds a small amount of water. That water is a seal. It stops sewer gas coming back up into your room.

If a sink or shower isn't used for a while, the water evaporates. The seal goes and the smell comes in. Spare bedrooms, utility rooms and downstairs toilets are the usual suspects.

The fix: run the tap for a minute. If the smell fades, you've found it. Run spare taps once a week to keep the seal topped up.

2. A dirty shower or basin waste

Hair, soap and skin build up just below the plughole. Over time, it turns into a slimy layer that smells. It's often mistaken for a drain problem, but it's right at the top.

The fix: take out the plug or waste cover and clean what you can reach. A long, thin brush helps. Avoid harsh chemicals. They rarely shift the build-up and can damage seals.

3. The washing machine or dishwasher

These empty into the same waste pipes as your sink. If the hose isn't set up with a proper loop or trap, smells can come back up through the machine. Leftover food or lint in the filter can smell too.

The fix: clean the filter, check the waste hose and run an empty hot wash.

4. A loose toilet seal

If the smell is strongest around the toilet, check the base. The seal between the pan and the soil pipe can work loose or perish. Sometimes you'll see a damp patch or staining on the floor.

The fix: this one is best fixed by a plumber. A leaking toilet seal can also rot floors over time.

5. A blocked or missing vent

Your drains need air to work properly. Most homes have a soil vent pipe running up the outside wall and out above the roof. Some have an air admittance valve, a small plastic cap, often in the loft or boxed in behind the toilet.

If the vent is blocked by leaves or a bird's nest, or the valve sticks, water can be pulled out of the traps as waste flows past. You'll often hear gurgling at the same time.

The fix: check the top of the vent pipe if you can see it safely from the ground. A faulty air admittance valve is cheap to replace.

6. A partial blockage

A drain that's partly blocked holds waste in the pipe instead of letting it flow away. That waste rots and smells. You might also notice slow drains or water backing up in a gully outside.

The fix: lift the nearest drain cover outside. If the chamber is full of water or waste, there's a blockage further along. See our guide to the signs your drains need a professional clean. Our drain unblocking team can clear it.

7. A cracked or broken pipe

This is the one people worry about, and it's more common in older homes. A cracked pipe under the floor, or a broken joint in a soil stack, lets sewer gas escape into the house. The smell often gets worse when it rains or when the heating's on.

You can't see this one yourself. It needs testing.

The fix: a CCTV drain survey shows cracks and broken joints in underground pipes. For pipes hidden inside walls or under floors, odour and smoke testing is often the quickest way to find the leak. We push harmless smoke into the drains and watch where it comes out.

8. A problem outside the house

Sometimes the smell is coming from outside. A blocked gully, an overflowing manhole or a septic tank that needs emptying can all smell strongly enough to drift in through vents and windows.

If you have a septic tank, read our guide to a septic tank that isn't draining properly. If you share a drain with neighbours, read who pays for a blocked drain.

Quick checks you can do today

1. Run every tap and flush every toilet, including ones you rarely use.
2. Clean the shower and basin wastes.
3. Lift the outside drain covers and look for standing water.
4. Check the base of each toilet for damp or movement.
5. Note when the smell is worst. After rain? After a shower? In the morning?

That last one is more useful than it sounds. If you call us, tell us. It helps the engineer narrow it down.

When to call a professional

Call us if:

• The smell keeps coming back after you've done the checks above
• You can smell it in more than one room
• It's stronger after rain
• You have damp patches, gurgling or slow drains as well
• You can see sewage or water backing up

Sewer gas isn't something to live with. As well as the smell, it means there's a gap somewhere it shouldn't be.

How we find the smell

We start with the simple checks, then move on to testing if needed:

• CCTV drain surveys for underground pipes
• Odour and smoke testing to find hidden leaks
• Drain unblocking or drain jetting if build-up is the cause
• Drain repairs if a pipe is cracked or broken

You get a clear answer, not guesswork.

Get rid of the smell for good

If you've tried the easy fixes and the smell is still there, let us find it. Call 0203 870 1067, email contactus@icedrainage.co.uk or get a quote today. We start with a free site survey.