Grimer locations — where to catch

In Paldea (Scarlet & Violet)

• East Province (Area Two) — Walk
• West Province (Area Two) — Walk

In Blueberry Academy (Scarlet & Violet – The Indigo Disk)

• Coastal Biome — Walk

In Sinnoh (Diamond, Pearl & Platinum)

• Route 212 — Walk

In Johto & Kanto (HeartGold & SoulSilver)

• Celadon City — Surf
• Johto Safari Zone — Surf, Walk
• Route 16 — Walk
• Route 17 — Walk
• Route 18 — Walk

In Hoenn (Ruby, Sapphire & Emerald)

• Fiery Path — Walk

In Kanto (FireRed & LeafGreen)

• Celadon City — Super Rod
• Pokémon Mansion — Walk

In Johto & Kanto (Gold, Silver & Crystal)

• Celadon City — Surf
• Route 16 — Walk
• Route 17 — Walk
• Route 18 — Walk

In Kanto (Red, Blue & Yellow)

• Kanto Power Plant — Walk
• Pokémon Mansion — Walk

Other games (7)

• Brilliant Diamond / Shining Pearl (Gen 8): Route 212
• Let's Go, Pikachu! / Let's Go, Eevee! (Gen 7): Cinnabar Island, Kanto Power Plant, Pokemon Mansion
• Ultra Sun / Ultra Moon (Gen 7): Hau'oli City, Malie City
• Sun / Moon (Gen 7): Hau'oli City, Malie City
• Omega Ruby / Alpha Sapphire (Gen 6): Fiery Path
• Black 2 / White 2 (Gen 5): Castelia Sewers
• XD (Gen 3): Phenac City

Grimer — full Pokédex entry