In a drum machine, whatever the manufacturer specifies — PETKIT states its tri-proof liner is replaced every 20 to 30 days to keep the drum leak-proof, which makes it a consumable rather than an option.
Liners in this category are two different things wearing the same word.
Machine liners
A drum machine’s liner is part of how it stays leak-proof. PETKIT publishes a replacement interval of 20 to 30 days, which is 12 to 18 a year and belongs in the cost of ownership.
Bin liners in a waste drawer
Ordinary bags, on machines that take them, and one of the cheapest things about owning one. Machines that require proprietary cassettes instead are where the lock-in lives.
Liners in a manual tray
Optional, and often counterproductive: a claw through a liner puts urine between the liner and the tray, which is worse than no liner at all.
What to check before buying a machine
Whether the waste drawer takes an ordinary bag. That single line changes the running cost more than most features on the box.
Last reviewed 2026-08-17