Why does my drain smell like sewage

Your drain smells like sewage because sewer gas is escaping into your home instead of venting out the roof. That gas forms when waste breaks down in the pipe, and it should never reach your nose. The most common reasons are a dried-out P-trap, a blocked vent pipe, or a break in the sewer line under your slab. In Covina, we see all three every week.

Below we'll walk through what causes each one, how to tell them apart, and what actually fixes the smell instead of just masking it.

Why a drain smells like sewage in Covina

A drain odor in Covina is a plumbing system telling you that the barrier between your home and the sewer has failed somewhere. Every fixture in your house has a water seal in the P-trap that blocks gas from rising up. Every drain also connects to a vent stack that carries gas up and out through your roof. When either piece stops working, the smell has a path inside.

Drain smells like sewage in Covina are especially common in homes built before 1980. The cast iron and clay sewer lines under many of these houses have been in the ground for 50 to 70 years, and tree roots from the mature ficus and sycamore trees that line so many Covina streets have had decades to find the joints.

If you're dealing with a slow drain alongside the smell, that's a strong clue the problem is in the line itself. Our team handles drain cleaning covina CA calls every week where the smell and the slow drain turn out to be the same issue.

The most common causes of drain odor in Covina homes

There are six causes we run into over and over in Covina. Which one you have changes what the fix looks like.

1. A dried-out P-trap

The P-trap is the curved section of pipe under your sink, tub, or shower. It holds a few inches of water that seals off sewer gas. If that water evaporates - usually in a guest bathroom, laundry sink, or floor drain you haven't used in a month or two - gas flows straight up the drain. This is the most common cause of sewage smell from drain Covina homeowners report in spare bathrooms.

The fix is simple: run the fixture for 60 seconds. If the smell disappears and stays gone, the trap was dry. If it comes back within a day or two, something else is going on.

2. A blocked or clogged vent pipe

Your roof vent can get blocked by bird nests, leaves, or a collapsed liner. When that happens, gas has nowhere to go but back into the house. You'll often notice the smell is worse on hot days or after you run a lot of water at once.

3. A partial clog in the drain line

Grease, soap scum, hair, and food waste build up on the pipe walls. That sludge itself smells, and it also traps gas that would normally move through. A kitchen sink that drains slowly and smells like rotten eggs is almost always this.

4. A broken or root-invaded sewer line

This is the one that worries us most. A crack, offset joint, or root intrusion in the main line lets sewage seep into the soil and gas rise back up around the pipe. In Covina, the older clay and cast iron lines are the usual suspects. Sewer smell in house Covina cases that get worse over weeks, not days, usually point here.

5. A failed wax ring or loose toilet seal

The wax ring under your toilet seals the bowl to the flange. When it fails, you'll often smell sewage near the base of the toilet, and you may see water staining on the floor. A toilet that rocks slightly when you sit on it is a warning sign.

6. A blocked or missing cleanout

Your home has a cleanout - usually a capped pipe near the foundation or in the yard. If the cap is missing or loose, sewer gas vents right there. This one is easy to spot once you know what you're looking at.

How to get rid of drain smell in Covina CA

You can fix the easy causes yourself in about 20 minutes. The harder ones need a camera and a trained eye.

Start with the simple checks

1. Run every fixture in the house for at least 60 seconds, including guest bathrooms and floor drains. This refills any dry traps.
2. Check the cleanout cap outside. If it's missing or loose, replace it with a threaded cap from any hardware store.
3. Pull the drain stopper from the smelly sink and clean the hair and gunk off it. A surprising amount of odor lives right there.
4. Pour a half-cup of baking soda down the drain, follow with a cup of white vinegar, wait 15 minutes, then flush with hot water. This helps with mild buildup, not with a real clog.
5. Sniff near the base of each toilet. If the smell is strongest there, the wax ring is the likely culprit.

When DIY stops working

If the smell returns within 48 hours, the problem is in the pipe, the vent, or the sewer line - not the trap. At that point, more baking soda won't help. You need someone to look inside the line.

We use a camera to see exactly what's happening. If the issue is buildup, professional drain cleaning covina CA clears it in one visit. If the line is cracked or root-invaded, we move to sewer line repair covina CA before the damage spreads under your slab or into the yard.

Is a smelly drain dangerous?

A smelly drain is usually a nuisance, but it can be dangerous. Sewer gas contains hydrogen sulfide, methane, and trace amounts of other compounds. At the low concentrations you smell in a bathroom, the main risk is irritation and headaches. At higher concentrations - which can build up in a closed-up house - methane is flammable and hydrogen sulfide can cause more serious symptoms.

Three signs mean you should treat it as urgent, not annoying:

• The smell is strong enough to make you dizzy, nauseous, or headachy.
• You smell gas in more than one room, not just one fixture.
• You hear gurgling in drains or see water backing up elsewhere in the house.

If any of those are happening, open windows, leave the house, and call us. That's an emergency plumbing covina CA situation, not a wait-until-Monday one.

Common mistakes that make drain odor worse

We see the same handful of mistakes over and over when homeowners try to fix a smelly drain on their own.

• Pouring bleach down the drain. Bleach kills the smell for a day and then the problem comes back - plus it damages rubber gaskets and can be dangerous if it mixes with other cleaners.
• Using drain cleaner from the grocery store. Caustic drain cleaner eats through some clogs but can also eat through older pipes. On a 1960s cast iron line, that's a bad trade.
• Ignoring a slow drain. A drain that's slow today is a drain that's fully blocked in three weeks. The smell is the early warning.
• Sealing the cleanout. We've seen homeowners tape over a cleanout cap to stop the smell. That just pushes the gas to the next weakest point.
• Assuming it's just the trap. If you've refilled the trap twice and the smell is back, it's not the trap.

One more thing worth knowing: if your home was built before 1975, the sewer lateral running from your house to the city main is likely original. Those lines have a lifespan, and when they fail, they fail with smell first and backups second. If you're not sure what you're dealing with, a sewer camera inspection covina CA gives you a straight answer in about an hour.

When to call a professional

Call a plumber when the smell comes back after you've refilled the traps, when more than one drain smells, or when you also see slow drainage or gurgling. Those three together almost always mean the problem is in the main line or the vent stack, and neither is something you can fix from the sink cabinet.

At Covina Citrusline Plumbing, we start with a camera inspection so you know exactly what's wrong before we quote anything. Most drain odor calls in Covina are resolved in a single visit - either with a thorough drain cleaning or, in the tougher cases, with a targeted sewer line repair. We give you the price upfront and don't start work until you say go.

If your home is older and the line has failed in more than one spot, we'll walk you through sewer line replacement covina CA as an option. It's a bigger job, but it's the right call when patching would just mean another call in six months.

Frequently Asked Questions

Why does my drain smell like sewage in Covina?

The most common cause is a dried-out P-trap, which lets sewer gas rise straight up the drain. Other frequent causes in Covina are blocked roof vents, partial clogs, and root intrusion in older clay or cast iron sewer lines. Refill the trap first - if the smell returns, the line or vent is the problem.

How do I stop drain smells in Covina CA?

Run every fixture for 60 seconds to refill dry traps, replace a missing cleanout cap, and clean hair off drain stoppers. If the smell returns within 48 hours, call a plumber - that means the issue is in the pipe or vent, not the trap, and it needs a camera inspection to diagnose.

What causes sewer smell in Covina homes?

Four things cause most sewer smell in Covina homes: dry P-traps in unused bathrooms, blocked vent stacks, grease and hair buildup in drain lines, and cracked sewer laterals. Homes built before 1980 with original clay or cast iron lines are the most likely to have the fourth problem.

Is a smelly drain dangerous in Covina?

Usually it's a nuisance, not an emergency. Sewer gas contains methane and hydrogen sulfide, which can cause headaches and nausea at higher concentrations. If the smell is strong, spreads across rooms, or comes with gurgling or backups, treat it as urgent and call a plumber right away.

How much does it cost to fix a smelly drain in Covina?

Typical 2026 pricing in Covina runs $150 to $350 for a standard drain cleaning, $250 to $600 for a camera inspection plus targeted repair, and $4,000 to $12,000 for a full sewer line replacement if the lateral has failed. We quote the price before we start.

Get help with plumbing in Covina

If the smell is back after you've refilled the traps, don't keep pouring things down the drain. We'll find the source, fix it, and confirm the line is clear before we leave. Call Covina Citrusline Plumbing at (626) 767-2111 and we'll get you on the schedule.