Drain smells after snaking

Quick Answer:

If you smell something foul after snaking a drain, start by checking the P‑trap and adding water to any seldom‑used drains to reseat seals. Snaking can push debris or air into traps and cleanouts, and sometimes reveal a cracked cleanout or vent issue. Smell near the cleanout and the roof vent to see whether it’s residual debris or actual sewer gas. If the smell doesn’t clear after refilling traps and flushing fixtures, get a camera inspection or call a professional.

Why This Happens

When you snake a drain you can dislodge hair, soap scum and organic matter. That debris can sit in a pipe bend or get loosened into the line and create a strong temporary odor. A dry or partially siphoned P‑trap lets sewer air into the room. Snaking can also reveal or worsen a bad seal at a cleanout, a loose coupling, or a small hairline crack that lets gas escape. This problem is similar to reports of Odor after main line work when disturbance in the pipe releases trapped smells.

Step-by-Step What to Do

Step 1: Check the P‑trap water level

Run water into the affected fixture until the bowl and trap are full, then flush or drain to refill the trap. For seldom‑used sinks or floor drains, pour 1–2 cups of water (or about a gallon for floor drains) to fully reseat the trap seal.
If the trap is cracked or leaking, you’ll need to replace it. A wet spot under the trap or constant low water level indicates a problem.

Step 2: Smell at the cleanout and vent stack

Locate the main cleanout (often in the basement, crawlspace, or outside). Carefully sniff near the cleanout cap—if the smell is strongest there, it points to sewer gas in the main line or a loose cleanout seal.
Check the roof vent stack from ground level or a safe vantage point. If the vent smells strongly, it’s likely sewer gas. Do not climb on the roof if you’re not comfortable; hire a pro for a safe inspection.
Differentiate odors: a sour or musty smell often means organic debris, while a sharp rotten‑egg scent can indicate hydrogen sulfide from sewer gas.

Step 3: Run a short scope/camera or hire an inspection

If you have a small inspection camera, run it from the cleanout a short distance to look for loose seals, cracks, or gaps in fittings. That can reveal a hairline crack or a failed cleanout seal letting gas escape.
If you don’t have a camera, or the issue is beyond the reach of a handheld scope, hire a plumber to do a professional camera inspection. They can pinpoint the source without unnecessary digging.

Step 4: Flush multiple fixtures and check vents for blockage

Flush toilets and run faucets for a few minutes to push residual debris through. If the odor disappears after flushing, the source was likely loosened debris.
Once the smell clears, confirm vents are clear of roof debris—leaves, bird nests or other blockages can prevent proper venting and let gas back up into the house. If roof work is needed, use a pro if you’re not experienced and safe on ladders or roofs.

If the odor returns after these steps, proceed to the next section on when to call a professional.

What Not to Do

Avoid dumping large amounts of bleach or scented cleaners hoping to mask sewer gas — they can be dangerous and delay proper diagnosis. Call a pro when the odor persists after re-filling traps, you detect hydrogen sulfide signs, or multiple fixtures smell — that can mean a cracked pipe or venting failure.
Don’t attempt roof or high‑place vent work without proper safety equipment and experience.
Don’t mix strong chemicals in the drain (for example bleach and ammonia)—that can create toxic fumes.

When to Call a Professional

If the odor persists after filling traps and flushing multiple fixtures.
If you detect strong rotten‑egg smells with eye irritation, nausea or dizziness—these can be signs of dangerous hydrogen sulfide exposure. Leave the area and call a pro or emergency services if symptoms are severe.
If multiple fixtures or the cleanout/vent area smell strongly—this may indicate a cracked main, failed cleanout seal, or venting failure that needs camera inspection and repair.
If you discover or suspect a leaking or cracked underground pipe, or you’re not comfortable performing vent or roof checks safely.

Safety Notes

Hydrogen sulfide (rotten‑egg smell) can be harmful in higher concentrations. If you experience headaches, eye irritation, dizziness, or difficulty breathing, get fresh air and seek medical help if symptoms are severe.
Do not mix household chemicals. Chemical reactions can produce toxic gases.
Use caution with ladders and roof access. If you are unsure about safely checking the vent stack, hire a professional.
If you suspect a sewage backup inside the home, stop using water and call a plumber. Sewage contact carries health risks.

Common Homeowner Questions

Why did the smell start after snaking? Snaking can dislodge trapped debris or let air move through a dry or weakened trap, releasing odors that were previously contained.
How long will the odor last? If it’s just loosened debris, flushing and refilling traps usually clears it within a few flushes; persistent smell suggests a seal, crack, or vent problem.
Can I fix a bad cleanout seal myself? You can tighten or reseal an accessible cleanout cap if you’re comfortable and have the right parts, but call a plumber if the cap is damaged, the pipe is cracked, or you can’t stop the smell.