Litter-Robot Waste Drawer Liners and Carbon Filters: What to Buy

A Litter-Robot 4 costs $699 once. The bags and filters cost you every month for as long as you own it, and Whisker sells both.

At Whisker’s list prices, a two-cat household running the official supplies at the cadence Whisker’s own liner page recommends spends about $117 a year on consumables [s1][s2]. Most of that is avoidable, and the case for avoiding it comes from Whisker’s documentation rather than from anyone selling an alternative.

Whisker says you can use any bag

The liner product page carries the question outright. “Can I use any type of bag in the waste drawer?” The answer: “Yes, you can use any bag that fits in the waste drawer” [s1].

The support documentation is more specific about what fits. “You can use Litter-Robot custom-fit waste drawer liners or any 8-13-gallon (30-49L) trash bags” [s3]. The liner installation guide narrows it further: “Customers often use 10 to 13-gallon white kitchen garbage bags or large white plastic grocery bags” [s4].

So the official liner is a convenience item by the vendor’s own account. A 13-gallon kitchen bag is the generic that fits.

Two constraints the machine enforces

Whisker names two things that go wrong with the wrong bag.

Colour changes what the sensor reads. “Please note that waste level readings may be inaccurate when using a dark bag, especially when the drawer is empty. As clumps start to collect in the drawer, the readings will become more accurate” [s1][s4]. The drawer-full estimate on the app reads against the bag. A black bag in an empty drawer is the worst case for it. White bags are what Whisker recommends [s3].

Bag height triggers a false alarm. “Make sure the bag does not come up past the top of the sides of the waste drawer, which can result in a false flashing ‘drawer full’ light on the control panel” [s4]. A drawer-full warning on a drawer that is not full is worth checking the bag for before checking anything else.

Neither constraint requires the official liner. Both require paying attention for about four seconds while you fit the bag.

Whisker’s own two pages disagree about how often to change it

The page that sells you liners says: “For two average-sized cats, twice per week is typical. For a single cat, once per week should be fine” [s1].

The support page that sells you nothing says the waste drawer needs emptying every week for two cats, and every two weeks for one [s3].

That is a factor of two, on both household sizes, from the same company. The higher figure is on the page with the add-to-cart button.

At Whisker’s list price of $55 for 100 liners, a two-cat household pays $28.60 a year at the support page’s weekly cadence and $57.20 at the product page’s twice-weekly one [s1]. Which cadence you follow moves the bill by $28.60.

Empty it when it needs emptying, and let your own cats set the number.

What the official liners cost

Whisker prices liners in four pack sizes [s1]:

AutoShip takes roughly a third off, bringing the 100-pack to $35.75 and the per-bag cost to about $0.36 [s1]. The liners measure 23.6 by 15.7 inches and fit the waste drawer of any Litter-Robot model [s1].

The case for buying them is the app’s drawer-full reading. A light bag cut to the drawer is what that sensor reads against, and the official liner is the only one sold to that spec. The machine itself runs on any bag that fits [s1].

The carbon filter is optional, and Whisker says so

Whisker’s carbon filter page lists the part as “Not required for Litter-Robot to function” [s2].

The filter is an activated-carbon-impregnated polyester pad that sits over the waste drawer to absorb odour. Whisker recommends replacing it monthly [s2]. At the list price of $30 for six, that is $5 a filter and $60 a year, which is more than the liners cost at either cadence. AutoShip brings the six-pack to $19.50, or $39 a year [s2].

One compatibility note for Litter-Robot 3 owners: these filters fit the Litter-Robot 4, 5, 5 Pro and EVO, and Whisker lists them as “Not compatible with Litter-Robot 3/Connect” [s2].

Third-party filters, and the limit of what we can tell you

Search Amazon for Litter-Robot 4 carbon filters and most of the results are third-party pads, sold in packs of six, eight and ten [s5].

We are not going to tell you which one fits. Whisker’s filter page does not list the pad’s dimensions [s2], so a third-party pad has no published spec to be checked against. Sellers state their own thickness and nothing independent confirms what the drawer accommodates. A pad that is too thick is a physical problem in a drawer that has to close.

What we can say is what the vendor says: the machine runs without a filter. The official pad is the only one with a known fit, which is what the $5 buys. Households that do not have an odour problem can leave this line at zero and see whether they notice.

The annual arithmetic

Two cats, Whisker list prices, at the support page’s replacement cadence:

Run the liners at the product page’s twice-weekly cadence instead and the official total reaches $117.20. Put both on AutoShip and it falls to about $57.59 [s1][s2].

Kitchen bags are sold by the box at supermarket prices, and by Whisker’s own specification the filter line can go to zero. The gap between those two columns is most of what this machine costs to run after you have bought it.

What we would buy

Buy the official liners if you use the app’s drawer-full reading and want it accurate. They cost about a dollar a week for two cats at the 100-pack price, and it is the one supply where the money buys a measurable property.

The filter is a different call. Whisker’s own specification says the machine does not need it, so the monthly replacement is an odour-control choice rather than maintenance.

Whatever you put in the drawer, make it white. That is the constraint the sensor reads against.

If you are still choosing the machine itself, our Litter-Robot 4 review covers the unit, and the litter guide covers the other consumable that affects those same sensors.

Sources

Prices were read from Whisker’s own store on 9 August 2026 and change with promotions; the AutoShip figures are the discounted subscription prices shown alongside them. No Amazon price appears anywhere on this page, because Amazon gates price and stock behind JavaScript and neither is readable at the moment of writing. The third-party filter claim is sourced to a search rather than a product page, because it is a claim about what the market contains.

• [s1] Whisker, Litter-Robot Waste Drawer Liners
• [s2] Whisker, Litter-Robot 4 Carbon Filters
• [s3] Whisker, Litter-Robot 4 ongoing maintenance
• [s4] Whisker, Waste drawer liner installation guide
• [s5] Amazon, search results for Litter-Robot 4 carbon filters