Laundry in the Netherworld is typically handled in special laundromats. The magic and grime accumulated in everyday life requires special spells, soaps, and training to deal with safely.
Soap potions and elixirs are mixed in accordance to need per batch. For instance, ghosts washing their shrouds will combine Temporary Corporeality and Remove Grime But Save Grave Dirt spells. This ensures the shroud can be affected by the wash and get clean, but won’t lose its ethereal bonds.
Waste water is processed carefully via the natural horrors that dwell in places like Grimwood Swamp. These wretched areas gleefully accept and disperse the noxious magical energies, breaking them down to their elemental parts via combinations of lichen, fungus, filtered sunlight, death magic, rot enchantments, and a wide variety of plants that have specifically evolved to thrive on sludge.
Home-based laundry pickup services are common. Typically, your garments return clean and pressed within three days.