She’d tried boiling water. She’d tried the rubber plunger until her arms ached. The only thing left was the small orange box under the sink, pushed behind the bleach: bicarbonate of soda .

Jenny ran the tap for a full minute. The water flowed fast and free. She leaned down, sniffed the drain—no sour death-stench. Just a faint, almost pleasant whiff of vinegar and minerals.

How to Clean Drains with Baking Soda and Vinegar | Liquid-Plumr®

: Slowly pour 1 cup (240ml) of white vinegar down the drain. You will hear an immediate fizzing reaction.

Her gran had sworn by it. “Caustic muck rots the pipes, love,” she used to say. “Bicarb’s kind. And stubborn.”

This is the most common method. It mimics the "volcano" experiment often seen in science fairs, using the power of expanding gas to clear pipes.

The water sat in the sink like a dark, oily mirror. It hadn’t moved for three hours. Jenny poked at it with a spoon, and a foul belch of old food and grease bubbled up.