Quick Answer: The sewage smell is almost always coming from your drain or inside your faucet itself, not the actual water. It’s caused by bacteria buildup in the drain or bacterial growth inside faucet components, or dry drain traps letting sewer gases escape.
First, Test This Simple Thing
Fill a glass with tap water and walk to another room. If the smell goes away, it’s bacteria in your drain or faucet. If the smell follows you, it’s actually in the water supply (rare but more serious).
Extra test: Turn the tap to just a tiny drip. If you can still smell sewage in that small amount of water, the bacteria is likely inside your faucet or supply pipes, not in the drain below.
Most Common Causes (95% of cases)
1. Bacteria in Your Drain OR Inside Your Faucet
In the drain: Hair, soap scum, and dead skin cells accumulate in your drain over time, creating the perfect environment for bacteria to multiply. When you turn on the tap, flowing water disturbs these bacteria, releasing hydrogen sulfide gas upward that you smell near the faucet area.
Inside the faucet: In new homes or unused fixtures, bacteria can grow inside the faucet body, spout, or aerator where water sits stagnant. This is especially common if the house has been empty or if water hasn’t been used for weeks. The bacteria creates the same rotten egg smell, but it’s actually coming from inside the plumbing components.
Quick Fix: Pour 1 cup baking soda down the drain, followed by 1 cup white vinegar. Cover for 15 minutes, then flush with very hot water. Also run the tap at full blast for 5-10 minutes to flush out any bacteria inside the faucet and supply pipes. Clean the aerator (unscrew, rinse, soak in vinegar) to remove bacterial buildup.
2. Dry P-Trap
The P-trap is that curved section of pipe under your sink that always holds water. This water acts like a barrier, preventing sewer gases from coming up through your drain. In bathrooms that aren’t used regularly (like guest bathrooms), this water can evaporate, leaving an open pathway for sewage smells.
Quick Fix: Simply run the water for 2-3 minutes to refill the P-trap. The smell should disappear immediately once the water barrier is restored.
3. Blocked Vent Pipe
Your plumbing system has vent pipes that go up through your roof, allowing air to flow through the system. When these get blocked by leaves, bird nests, or debris, it creates pressure issues that can pull sewer gases into your home through the drains.
Signs: Gurgling sounds when water drains, unusually slow drainage, or smells that seem to come and go
Fix: This requires going on the roof, so it’s safer to call a plumber to clear the blockage
When It’s Actually in the Water (Rare)
If you take water from the tap to another room and can still smell the sewage odor after 1-2 minutes, then the problem is actually in your water supply, not the drain. Here’s what could be causing it:
Hot water only: Bacteria can grow inside your water heater tank, especially if the temperature is set too low (below 120°F). These bacteria produce hydrogen sulfide gas, creating that rotten egg smell. While usually not dangerous for healthy adults, it should be addressed by a plumber who can flush the tank, replace the anode rod, or adjust the temperature setting.
All water (hot and cold): This suggests possible contamination in your main water supply. It could be from a broken sewer line near water pipes, cross-connected plumbing, or issues at the water treatment plant. Stop using the water immediately and contact your water company – this is a health concern that needs professional attention.
After heavy rain: Water treatment plants can sometimes become overwhelmed during storms, allowing contaminants to slip through the system temporarily. The smell should clear up within a day or two as treatment returns to normal, but contact your water utility to report the issue.
Is this Water Safe?
For showering:
Usually yes, if it’s just bacteria in drains or faucets, but avoid if you have open cuts or very sensitive skin. If the smell is strong or the water looks cloudy, skip the shower until you fix the problem.
For drinking:
Don’t drink it until you identify and fix the source, even if it’s “just” bacterial growth.
Red flags that need immediate attention:
Cloudy or discolored water, multiple people getting sick, smell getting worse over time, or sewage smell present throughout your entire house.
Quick 5-Minute Fix Checklist
Try these steps in order – most sewage smell problems will be solved by the time you finish:
- Run water for 5-10 minutes – Turn on both hot and cold taps full blast to flush out any stagnant water and bacteria that may be sitting in your faucet, aerator, or supply pipes. This is especially important in new or unused homes.
- Clean the faucet aerator – That little screen at the tip of your faucet can harbor bacteria, especially in new installations. Unscrew it by hand (or use pliers with a cloth), rinse under running water, then soak in white vinegar for 30 minutes to kill bacteria and dissolve mineral deposits.
- Treat the drain with baking soda and vinegar – Even if the smell is coming from inside your faucet, it’s worth cleaning the drain too. Follow the method described above – the fizzing action breaks up any bacterial biofilm.
- Do the glass test and drip test again – Fill a clean glass with water and walk to another room, and also test with just a tiny drip to confirm whether you’ve solved the problem.
When to Call a Professional
- Smell persists after trying these fixes for 24-48 hours
- Multiple drains or faucets are affected throughout your home
- Water looks cloudy, discolored, or has visible particles
- You suspect actual water contamination (smell follows the water)
- Strong sewage odors accompanied by gurgling sounds or slow drainage
Prevention (2 minutes monthly)
Weekly maintenance:
- Run water in unused sinks – Even if you don’t use a bathroom regularly, run the water for 30 seconds once a week. This keeps the P-trap filled and prevents sewer gases from entering your home
Monthly deep clean:
- Clean drains with baking soda/vinegar – Do the same treatment described above as a preventive measure, even when there’s no smell. This prevents bacteria from building up in the first place
Quarterly maintenance:
- Remove and clean faucet aerators – Mineral deposits and bacteria can accumulate over time. Cleaning them regularly maintains good water flow and prevents odor-causing buildup
Extra tip: If you’re going on vacation for more than a week, run water in all drains when you return. Extended periods without use can lead to dry P-traps and stagnant water in pipes.
Bottom Line: Don’t panic. It’s almost always a simple drain issue that takes 15 minutes to fix. If basic cleaning doesn’t work, call a plumber to check your plumbing vents or P-traps.