The Purpose Behind the Upside-Down Glass Hack

This setup—covering a dry sink drain with paper and placing an upside-down glass on top—is a viral pre-vacation home maintenance hack designed to solve two main issues when a home sits empty:

• Blocks Sewer Odors & Evaporation: Sink drains rely on a U-shaped pipe (P-trap) that holds water to block sewer gas. When a sink goes unused for weeks—especially in warm weather—that water can evaporate, allowing foul smells to leak up. The paper and weighted glass act as a makeshift seal to keep odors trapped and slow down evaporation.
• Prevents Drain Insects: Stagnant, dark plumbing lines attract pests like fruit flies, drain flies, and cockroaches looking for moisture. Covering the opening physical blocks them from crawling up into your kitchen or bathroom while you are away.
• Acts as a “Leak / Clog” Indicator: Some variations of this trick use absorbent paper towel underneath. If you return and the paper is wet, it indicates water backed up or seeped up from the pipe—signaling a hidden drainage blockage before it turns into a major overflow.