According to Dr. Jim Frederick, an entomologist in the US, cockroaches are attracted to drains for three main reasons: moisture, food debris, and shelter.
"Your home's plumbing system is like a superhighway designed for cockroaches, helping them avoid predators and travel easily," Dr. Frederick explained.
Entomologist Trent Frazer added that drains contain a source of filth that cockroaches love, such as leftover food, grease, and soap residue. "Their incredible adaptability allows them to navigate wet environments, even surviving underwater for hours, and easily climb up through pipes," Mr. Frazer said.
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Daily water usage keeps the P-traps – the curved sections of pipe under sinks and showers – filled with water, creating a protective barrier. This water seal prevents sewer gases and insects from entering. However, when you're away, the water in these traps can evaporate, creating an open invitation for cockroaches.
"Without this water barrier, cockroaches have a clear path from the sewer into your living space," Dr. Frederick warned.
While some people cover drains with vases or dishes, this doesn't create a proper seal. Dr. Frederick emphasized that cockroaches only need a gap of about 1.5 mm to squeeze through.
"The best way to keep them out is to run water down each drain before leaving," Dr. Frederick advised. The resulting water barrier in the P-trap helps block cockroaches and sewer gases. "Then, use a tight-fitting drain plug to create an airtight seal, preventing insect penetration and helping maintain the water in the P-trap, strengthening the barrier."
Before leaving, you should also empty the trash, clean kitchen surfaces, and store food in airtight containers to eliminate food sources for cockroaches.
Even when not away, Mr. Frazer recommends periodically flushing water down sinks, tubs, and drains in guest bathrooms or infrequently used rooms. This helps keep P-traps full, deterring insects. If you frequently see cockroaches emerging from drains, it could indicate an infestation or a more serious plumbing issue.
Bao Nhien (According to Realsimple)
