The sun’s out, the garden’s in bloom and the smell of sizzling sausages is in the air… but wait—what is that whiff wafting up from the sink?!!
Unfortunately, Summer isn’t just BBQ season—it’s also prime time for weird and unwelcome smells from your drains. Warm weather speeds up the biological and chemical processes happening inside your plumbing, and if there’s a blockage, build-up, or trap problem you might start to smell the consequences.
Let’s break down what’s happening inside your smelly drains—and what that pong actually is. (Yellow HAZMAT Suits are a bit OTT, but perhaps grab a clothes peg..)
Why Does My Drain Smell?
Drain smells are typically caused by gases released during the breakdown of organic material—food waste, hair, grease, soap, and other bits that make their way into your pipes.
Common Drain Gases Include:
- Hydrogen sulphide (H₂S) – Smells like rotten eggs. Produced by anaerobic bacteria breaking down organic matter in low-oxygen environments.
- Methane (CH₄) – Odourless but flammable. Formed during sewage decomposition.
- Ammonia (NH₃) – Pungent, nose-tingling scent.
- Carbon dioxide (CO₂) – Odourless, but can displace air and worsen trapped gas build-up.
- Sulphur dioxide (SO₂) – Can give off a sharp, choking smell.
In small domestic concentrations, these gases aren’t harmful—but they’re certainly not pleasant.
Why Does It Get Worse In Summer?
Heat speeds up the decomposition of organic matter in your drains and promotes bacterial growth. That means:
- Food scraps rot faster
- Grease turns gooey and traps debris
- Dry U-bends or traps (especially in little-used sinks or outdoor drains) allow gases to rise up unfiltered
It’s like a slow-cooked stew—except no one wants a noseful of “compost casserole.”
What’s Happening Inside the Pipes?
Here’s what might be brewing beneath your plughole:
- Bacterial Fermentation
Anaerobic bacteria (the kind that thrive without oxygen) break down food waste and other organic matter trapped in pipes. As they digest they produce hydrogen sulphide and methane.
Think of it like a compost bin—but in pipe form.
- Trap Failure
Plumbing traps (U-bends) rely on a water seal to stop gases from coming back up the pipe. If that water evaporates or never forms—common in unused drains—there’s nothing stopping the gases from rising.
In hot weather, evaporation speeds up, especially in guest toilets, garages, or garden outbuildings.
- Biofilm Build-up
Over time, pipes can accumulate a layer of slimy residue known as biofilm—a mix of bacteria, mould, grease, and particles. This organic layer holds on to odours and can act like a sponge for gases.
Cleaning the pipe walls (not just flushing water down) is often needed to get rid of this clingy gunk.
DIY: How To Fix A Smelly Drain
- Run Water to Refill Traps
If a drain hasn’t been used in a while, pour water down to restore the seal in the U-bend.
- Use Natural Cleaners
Try a mix of baking soda and vinegar for drain cleaning followed by hot (not boiling) water to flush through grime and break up small clogs.
- Manually Clean the Trap
Unscrew the trap under the sink and clean out food or gunk (don’t forget a bowl and gloves!).
- Jet Wash Outdoor Drains
Summer often leads to blocked outside drains from leaves, soil and grease. Clear them before they bake solid.
When To Call In The Experts
If the smell is strong, returns quickly, or seems to be spreading from more than one location, it’s time to call in the experts. You could be dealing with:
- A cracked or collapsed pipe
- Sewer gas ingress
- Root intrusion
- A hidden blockage deep in the system
A CCTV drain survey lets us look inside your pipes to identify the cause—without guesswork or digging.
Final Whiff of Advice
Drain odours in summer are common—but never normal. They’re your plumbing’s way of saying, “Help!”
And don’t forget: the longer you leave it the more intense the problem (and the smell) can become.
Contact Happy Drains and we’ll track down the source, clean things up and help your drains smell like nothing at all—which is exactly how they should be.
Call 0788 254 933 / 0800 8498 099
✅ Fast service
✅ No mess
✅ Local experts
✅ 5-star reviews
Breathe easy again!
Best, David & Will
