French presses get dirtier than they look. Coffee oils coat the mesh, the plunger, and the carafe walls, and within a few weeks of use, those oils start tasting rancid in your cup.
After every brew
Empty the grounds into the trash or compost (never down the sink, even with hot water; they clog drains). Rinse the carafe with hot water. Disassemble the plunger by unscrewing the mesh from the rod, rinse all three pieces, reassemble. Total time: under two minutes.
Weekly deep clean
Once a week, give the press a real wash. Disassemble fully. Wash all parts in warm soapy water. Use a soft brush to scrub the mesh and any visible coffee residue on the carafe walls. Rinse thoroughly. Soap residue is the most common reason a French press smells off.
Monthly descale and oil removal
Coffee oils accumulate in the mesh even with weekly washing. Once a month, soak the mesh and screen assembly in a 1:1 mixture of warm water and white vinegar for 15 minutes. Scrub gently with a soft brush, rinse, dry. The vinegar cuts through the oils that soap leaves behind.
Signs your press needs cleaning
The smell test is the most reliable. If your dry French press smells faintly of stale coffee or rancid oil, it is time. The same brew, made in a clean press, will taste noticeably brighter and cleaner.
Replace the mesh eventually
Mesh screens wear out. After 1-2 years of daily use, even a perfectly cleaned mesh starts letting fine particles through. Replacement screens are cheap (under $10) and worth the upgrade well before you think you need one.