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Washing Machine Smells Like Sewage? It's Usually a Dry Drain Trap

A sewage or rotten-egg smell near the washer usually comes from a dry drain trap or slime in the machine. Check these before you panic.

By Jamilur Rahman Updated November 5, 2026 · 6 min read

Time
30 min
Cost
Under $20
Difficulty
Easy
A white washing machine in a laundry room with a grey drain standpipe and hose in the wall behind it
In this guide
  1. Quick answer
  2. Free vs. permanent fix
  3. What you'll need
  4. Why it happens
  5. Try this first (free)
  6. When free fixes aren't enough
  7. Buy the fix
  8. How to fix sewer smell in the laundry room
  9. What to skip
  10. FAQ
  11. Related problems

Quick answer

When your washing machine smells like sewage, it is usually a dry drain trap: the water seal in the pipe below the standpipe has evaporated, so sewer gas rises into the room. Pour a quart of water down the standpipe, then run a hot cleaning cycle to clear slime in the machine. A one-way trap seal keeps the gas out for good. If it smells like rotten eggs and you have a gas dryer, leave and call your gas company first.

Free fix vs. permanent fix

Free fix · 20 minutes plus a hot cycle

Refill the trap and clean the washer

  • Pour a quart (about 4 cups) of water into the standpipe
  • Run an empty hot cycle with a washer cleaner
  • Wipe the rubber seal and the detergent drawer
  • Leave the door ajar between loads

How long it lasts: Weeks to months. If the washer sits idle often, the water in the trap dries up again.

Most readers choose Permanent fix
One-way drain trap seal for a washer standpipe (illustration)
Illustration

A one-way drain trap seal for the standpipe

A trap holds a plug of water that blocks sewer gas. In a laundry room it evaporates when the washer sits idle for days, or it may be missing or siphoned. A one-way silicone seal in the standpipe opens for draining water and shuts again, so gas has no way through.

What to get: One-way drain trap seal for a washer standpipe

How long it lasts: Years. It closes when no water is flowing, so gas cannot rise even if the trap dries out.

Check price on Amazon

As an Amazon Associate I earn from qualifying purchases.

What you'll need

  • Pitcher or jug

    To pour water into the standpipe

    You have it
  • Washing machine cleaner tablets (illustration)
    Illustration

    Washing machine cleaner tablets

    Clears slime in the drum, hose and seal

    Check price
  • Our pick
    One-way drain trap seal for standpipe (illustration)
    Illustration

    One-way drain trap seal for standpipe

    Check your standpipe's inside width before ordering

    Check price

  • Microfiber cloths

    To wipe the door seal and drawer

    You have it

Why it happens

1

A dry or missing trap

Every drain has a U-bend that holds water and blocks sewer gas. In a laundry room that water evaporates if the washer sits unused for weeks. A missing trap lets gas rise all the time.

2

Slime in the washer

Bacteria grow in leftover water in the drum, seal and drain hose. Some produce a rotten-egg smell.

3

A blocked or poorly vented drain

A blocked vent can pull water out of the trap, and gurgling is a clue. The smell then returns again and again.

4

Smelly hot water

If only the hot water smells like eggs, the water heater is the source, not the washer.

Try this first (free)

Do these in order, starting with the simplest.

  1. 1. Rule out gas first

    If it smells like rotten eggs and you have a gas dryer or gas lines in the room, do not touch switches. Leave the house and call your gas company or the fire department.

  2. 2. Refill the trap

    Tool used: Pitcher or jug

    Slowly pour about a quart (4 cups) of water into the standpipe. If the smell fades in an hour, a dry trap was the cause.

  3. 3. Run a hot cleaning cycle

    Tool used: Washing machine cleaner tablets

    Run an empty hot cycle with a washer cleaner tablet, following the label. Never mix bleach with vinegar or ammonia.

    Washing machine cleaner tablets (illustration)
    Illustration

    Tool for this step

    Washing machine cleaner tablets · Clears slime in the drum, hose and seal

    Check price on Amazon

  4. 4. Wipe the seal and drawer

    Tool used: Microfiber cloths

    Wipe the rubber door seal and the detergent drawer, and leave the door ajar so the drum can dry.

  5. 5. Find the source

    Sniff the standpipe, the drum and the hose end. A smell at the standpipe is the trap. A smell in the drum is the washer. A smell from only the hot tap is the water heater.

  6. 6. Fit a trap seal

    Tool used: One-way drain trap seal for standpipe

    If the smell returns within weeks, drop a one-way trap seal into the standpipe so the trap can dry out without letting gas in.

    One-way drain trap seal for standpipe (illustration)
    Illustration

    Tool for this step

    One-way drain trap seal for standpipe · Check your standpipe's inside width before ordering

    Check price on Amazon

When free fixes aren't enough

If the smell is back within weeks, the trap is probably drying out or leaking, or the standpipe has no trap at all. A trap seal solves that at the source. If you smell sewage in several rooms, other drains gurgle, or water backs up, call a plumber. The vent or main line may be blocked. Sewer gas in a closed room can make people dizzy or sick, so ventilate, and get out and get help if anyone feels unwell.

Buy the fix

Still stuck after the free fixes? These are the products we would look at.

Our picks compared
PickProductFixesWho it's forBuy
Best pick
One-way drain trap seal for a washer standpipe (illustration)
Illustration
One-way drain trap seal for a washer standpipe
sewer gas rising through a dry or missing trap Anyone whose smell returns after refilling the trap. Check price
Budget pick
Washing machine cleaner tablets (illustration)
Illustration
Washing machine cleaner tablets
slime in the drum and hose that smells like eggs Anyone whose smell is strongest inside the drum. Check price
Best pick
One-way drain trap seal for a washer standpipe (illustration)
Illustration

One-way drain trap seal for a washer standpipe

Fixes: sewer gas rising through a dry or missing trap

Look for: Sized to your standpipe's inside width, often 2 inches; A one-way valve that opens for draining water; A press-fit design that needs no tools.

Who it's for
Anyone whose smell returns after refilling the trap.
Honest downside
You are unsure of the pipe size or the drain is clogged. Fix the clog first, or ask a plumber.
Check price on Amazon
Budget pick
Washing machine cleaner tablets (illustration)
Illustration

Washing machine cleaner tablets

Fixes: slime in the drum and hose that smells like eggs

Look for: Says it works in your machine type; Removes odor and residue; Used monthly, per the label.

Who it's for
Anyone whose smell is strongest inside the drum.
Honest downside
The smell is only at the standpipe. That points to the trap, not the machine.
Check price on Amazon

As an Amazon Associate I earn from qualifying purchases. We don't show prices because they change, so use the button to see today's price.

How we picked: How we picked: this page is based on plumbing guides on drain traps, washer manuals, product instructions from trap seal makers, and the problems and fixes people report in reviews. We do not test products by hand.

How to fix sewer smell in the laundry room

  1. Refill every drain trap in the room with water.
  2. Clean the washer with a hot cycle.
  3. Check that the drain is not gurgling or slow.
  4. Fit a trap seal if the smell returns.
  5. Call a plumber if more than one drain in the house smells.

What to skip

Air fresheners and bleach down the drain

Sprays and plug-in fresheners cover the smell, and the gas keeps coming. Bleach in the standpipe does not refill a dry trap, and mixing it with vinegar or ammonia makes toxic fumes.

Frequently asked questions

Why does my washing machine smell like sewage, or sewer?
The usual cause is a dry drain trap, so sewer gas rises through the standpipe. Slime in the drain hose or drum can also smell like sewage. Refill the trap first, then clean the machine.
Why does my washing machine smell like rotten eggs, sulfur or eggs?
Bacteria in leftover water can make a sulfur smell. If only hot water smells, the water heater is the source. If you have a gas dryer, treat rotten eggs as a possible gas leak and call the gas company.
Laundry smells like sewage after washing: what now?
Run a hot cleaning cycle on the empty washer, then rewash the clothes with detergent and an extra rinse. Clothes pick up the smell from slime in the drum or hose.
Why does my laundry room smell like sewage?
A dry floor drain or standpipe trap is the usual source. Check any floor drain, the standpipe and the washer. Pour water into each one that has not been used lately.
Why does my laundry room smell like rotten eggs?
It may be bacteria in the washer or hot water. But gas appliances also give off a rotten-egg smell on purpose, so if the smell is strong or you have a gas dryer, leave and call the gas company first.

As an Amazon Associate I earn from qualifying purchases. Affiliate disclosure

One-way drain trap seal for a washer standpipe (illustration)
Illustration

Our pick: One-way drain trap seal for a washer standpipe

Check price