Litter Box Smells Even After Cleaning? Why Plastic Holds Odor
Scratched plastic soaks up urine and keeps the smell. Wash the box properly for free, then switch to stainless steel if the smell survives.
By Jamilur Rahman Updated November 5, 2026 · 6 min read
- Time
- 30 min
- Cost
- $20-$50
- Difficulty
- Easy
In this guide
Quick answer
Plastic gets tiny scratches from scooping and claws, and urine soaks into them, so the smell survives a wash. Scoop daily and wash the box with hot water and unscented dish soap. If the plastic is deeply scratched or cloudy and still smells, a smooth stainless steel box gives urine nothing to soak into.
Free fix vs. permanent fix
Scoop daily and wash the box properly
- Scoop at least once a day
- Dump and wash the box every 2 to 4 weeks with hot water and unscented dish soap
- Keep litter 2 to 3 inches deep
- Clean the wall, floor and mat around the box
How long it lasts: Fixes the smell if the box is fairly new. Once the plastic is scratched and cloudy, the smell keeps coming back.
A stainless steel litter box
Urine soaks into the fine scratches in plastic and cannot be washed out. Stainless steel is smooth and non-porous, so the box wipes clean and stops being the source of the smell.
What to get: Stainless steel litter box
How long it lasts: Years. Stainless resists the deep scratches plastic gets.
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What you'll need
-
Unscented dish soap and hot water
Skip ammonia, bleach mixes and strong fragrance
Free - Illustration
Enzymatic pet odor cleaner
For the floor, wall and mat around the box
- Our pick Illustration
Stainless steel litter box
For plastic that is scratched or cloudy and still smells
Why it happens
Scratched, porous plastic
Scoops and claws leave fine scratches. Urine and ammonia seep into them and cannot be fully washed out, so the box smells on its own. The cloudy, dull patches in the corners are usually the worst spots.
Litter that is too shallow or changed too rarely
If litter is thin, urine reaches the bottom before it clumps and soaks into the plastic. An overdue full change has the same effect, because saturated litter stops absorbing.
Strong or ammonia-based cleaners
Ammonia smells like urine to a cat and can encourage re-marking. Heavily scented cleaners can also put a cat off the box.
Odor in the area around the box
Spilled litter, a damp mat, or small accidents on the wall or floor keep smelling after the box itself is clean.
Try this first (free)
Do these in order, starting with the simplest.
-
Scoop at least once a day
Twice a day is better with more than one cat. Remove clumps and solid waste right away.
-
Dump and wash the whole box on a schedule
Tool used: Unscented dish soap and hot waterFor clumping litter, empty and wash the box about every 2 to 4 weeks, and more often for non-clumping litter or several cats. Scrub the corners and sides with a dedicated brush, rinse well and dry fully before refilling.
-
Check the plastic
With the box dry, look at the corners. Deep scratches or a cloudy, dull surface are where urine soaks in. If it still smells after a hot wash and full dry, the plastic is the problem, not your routine.
-
Keep litter 2 to 3 inches deep
That depth lets urine form a clump before it reaches the bottom.
-
Clean the surroundings
Tool used: Enzymatic pet odor cleanerWash the mat, wipe the wall and floor around the box, and use an enzyme cleaner on any spot where urine has soaked in.
IllustrationCheck price on AmazonTool for this step
Enzymatic pet odor cleaner · For the floor, wall and mat around the box
When free fixes aren't enough
If your plastic box is only months old, the free routine usually works and you do not need to buy anything. If it is deeply scratched, cloudy or still smells after a hot wash and a full dry, the urine is in the plastic and no washing will get it out. That is when stainless steel pays off. If the smell is around the box rather than in it, an enzyme cleaner on the floor and wall is the fix. A sudden, stronger smell or changes in urination are a vet question.
Buy the fix
Still stuck after the free fixes? These are the products we would look at.
| Pick | Product | Fixes | Who it's for | Buy |
|---|---|---|---|---|
| Best pick | Stainless steel litter box | urine soaking into scratched plastic | Owners whose plastic box still smells after washing, or who want a box that lasts for years. The smooth surface also wipes clean faster, so it suits busy households. | Check price |
| Budget pick | Enzymatic pet odor cleaner (unscented) | odor soaked into floors, walls and mats around the box | Anyone whose smell lingers around the box even after the box is clean. | Check price |
Stainless steel litter box
Fixes: urine soaking into scratched plastic
Look for: Smooth, seamless or welded construction with no gaps for urine to collect; Roomy enough for your cat to turn around, about 1.5 times its body length; Sides tall enough for your cat's habits, or a low entry if it is older.
- Who it's for
- Owners whose plastic box still smells after washing, or who want a box that lasts for years. The smooth surface also wipes clean faster, so it suits busy households.
- Honest downside
- Your cat is very old and needs a low entry. Check the height first. Some cats also dislike the sound of a metal scoop.
Enzymatic pet odor cleaner (unscented)
Fixes: odor soaked into floors, walls and mats around the box
Look for: Enzymes that break down urine, not just perfume; Unscented or lightly scented; Safe for the floor or wall near the box.
- Who it's for
- Anyone whose smell lingers around the box even after the box is clean.
- Honest downside
- The smell is only inside the box. Fix the box first.
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How we picked: How we picked: this page is based on veterinary guidance on litter box care, product care instructions, and the problems and fixes cat owners report in reviews. We do not test products by hand.
Plastic, stainless steel or other: how they compare
- Plastic: cheap and light, but scratches and holds odor over time.
- Stainless steel: does not absorb urine and is easy to wash. It costs more, is heavier and can be noisier with a scoop.
- Ceramic or glazed: smooth, but heavy and can crack.
How many boxes, how big, and where
A common rule is one box per cat, plus one extra. Pick a box about 1.5 times your cat's length, somewhere quiet and easy to reach, away from food and water.
When the smell is a health sign
Call the vet if the smell is suddenly much stronger, the urine looks bloody, your cat strains, goes more often or pees outside the box. A male cat that strains and passes little or no urine is an emergency.
What to skip
Scented litter, plug-in fresheners and ammonia cleaners
Perfume covers the smell for a few hours, and some cats refuse scented litter. Ammonia cleaners smell like urine to a cat. Fix the box, the litter depth and the schedule instead.
Frequently asked questions
Do covered litter boxes reduce smell?
Does baking soda help?
Will my cat use a stainless steel box?
Why does my litter box smell like ammonia right after I clean it?
Related problems
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