I sometimes pour a kettle of boiling water down the kitchen drain to melt the fats. I recall seeing a youtube video of a guy boiling pvc fittings to separate them and reuse them, which caused some concern for my habit of pouring boiling water down. But he had to boil those fittings in a pot for like 30 min with all sides of the fitting getting heat, so I’m not worried.
Budget permitting, it’s best to pour the hot water down ~15-20 min before going to bed, then just before going to bed pour ~50—100ml of enzymes. Enzyme-based maintenence cleaning is most effective when the sludge they will consume is warm. Let the enzymes feast on the nasties all night long.