Want To Know Why Drains Smell in Michigan Summer Heat

If you’ve noticed a foul odor wafting from your sink, shower, or floor drains during the warmer months, you’re not alone. Many Michigan homeowners complain about funky drain smells as the summer heat kicks in. This isn’t just an annoyance—it could be a sign of a bigger issue lurking in your plumbing system.

Let’s break down why drains smell in Michigan summer heat, what causes it, and what you can do to stop it before your home starts to reek like a swamp.

1. Heat Accelerates Bacteria Growth

The first and most obvious reason? Heat.

In the summer, higher temperatures create the perfect breeding ground for bacteria inside your drains. Food particles, soap scum, grease, and organic waste that coat the inside of pipes start to rot faster. That decomposition process releases foul-smelling gases like methane and hydrogen sulfide.

In Michigan, where humidity adds another layer of moisture, bacteria multiply rapidly, especially in drains that aren’t regularly flushed or cleaned.

2. Dry P-Traps = Sewer Gas

Another common culprit is a dried-out P-trap. The P-trap is that U-shaped pipe under your sink or tub. Its job is to trap a small amount of water to act as a barrier against sewer gas.

However, during the summer, the heat can evaporate that water—especially if a drain hasn’t been used in a while, such as in a guest bathroom or basement floor drain.

Once that water evaporates, nothing is stopping sewer gas from rising back up into your home. And yes, that’s exactly as nasty as it sounds.

3. Decomposing Gunk in Kitchen Drains

Your kitchen sink drain takes a beating year-round, but summer can really bring out the worst smells. Food waste breaks down faster in the heat, and even small bits of garbage disposal sludge can turn into a stink bomb within a day or two.

And when those fats and proteins break down, you’ll get that unmistakable rotten egg or sour milk odor that lingers no matter how much air freshener you spray.

4. Clogged or Partially Blocked Vent Pipes

Your plumbing system is more complex than just pipes and drains. It also includes vent pipes—these allow sewer gas to escape your home via the roof.

If those vents become clogged with debris, leaves, bird nests, or even dead critters (yes, it happens), then pressure builds up and forces gas back through your drains. In the summer, that pressure builds even faster thanks to increased thermal expansion in the plumbing lines.

5. Biofilm Buildup in Bathroom Drains

In your bathroom, slimy pink or dark residue forming around your drain cover is biofilm—a mix of bacteria, mold, mildew, and other organic waste. In cooler months, it’s slower to build up. But in summer, that biofilm forms fast.

Once it’s built up in the drain pipe, it produces an earthy, musty, or downright rotten smell. This is often the cause of recurring shower or bathtub drain odor that cleaning the surface alone won’t fix.

6. Sewer Line Problems

Sometimes, the smell isn’t just from your drains—it’s from a bigger issue down the line.

Cracked or backed-up sewer lines can leak gases that seep up into your drains. In summer, the ground expands with heat and can shift old pipes, causing minor cracks or joint failures. Tree roots seeking water may also invade your sewer line during dry summer months, which worsens the issue.

If you’re noticing persistent smells along with slow draining or gurgling noises, don’t ignore it. It could be time to call a pro.

7. Michigan’s Summer Storms & Flooding

Here’s one most people don’t think about: summer storms.

Michigan summers can bring sudden heavy rains. These overwhelm storm drains and sometimes even your home’s sewer system, especially if you’re on a combined sewer line. That backup pressure can force gases back into your home, often through basement or floor drains.

If your drain smells worse after a rainstorm, this is a sign of a bigger drainage issue.

What You Can Do About It

Now that we’ve explained why drains smell in Michigan summer heat, here’s what you can actually do:

Run Water in Unused Drains

If you don’t use a sink or tub regularly, pour a few cups of water (and maybe a bit of vinegar) down it every couple of weeks. This keeps the P-trap full and blocks sewer gases.

Clean Drains With Baking Soda & Vinegar

Once a month, pour a half-cup of baking soda down the drain, followed by a cup of white vinegar. Let it fizz for 15 minutes, then flush with boiling water. This can help kill odor-causing bacteria.

Use Enzyme Cleaners

Unlike chemical drain cleaners that can damage pipes, enzyme-based products break down organic buildup in a safer way.

Snake the Drain

If you suspect biofilm or minor blockages, use a drain snake to remove gunk from inside the pipes. Even hair and soap buildup can contribute to that funky odor.

Inspect Your Roof Vents

If you’re comfortable with heights, check your plumbing vent stack. Clear off any debris or obstructions. Or better yet—call in a licensed plumber to inspect your system.

Schedule a Professional Drain Cleaning

If your efforts don’t stop the smell, it’s time for a professional inspection and cleaning. Technicians use high-pressure water jetting and video camera inspections to locate and eliminate the root of the problem. Hydro jetting is a powerful way to clear clogs.

Don’t Wait for the Smell to Get Worse

Nobody wants to walk into their home and be hit with a whiff of rotten eggs or sewer gas. In the Michigan summer heat, drain odors can spiral out of control fast. While minor smells may be manageable with DIY methods, persistent or recurring issues often point to a more serious plumbing problem.

Your nose isn’t lying—if your drains are stinking, it’s time to act.

Whether it’s a dried-out P-trap, bacterial buildup, or a venting issue, professional drain cleaning can eliminate the odor at the source.