How to prevent rodents from entering through plumbing pipes?

Rodents (rats, mice) can enter a house through openings around plumbing pipes. Here's how to block them:

Typical entry points:

• Around pipes passing through the foundation (water entrance, gas, drain)
• Around plumbing vents on the roof
• Space between the drain pipe and the wall under the sink

Solutions:

• Steel wool: The best barrier — rodents cannot chew through it. Pack extra-fine (#00) steel wool into gaps around pipes. Cost: $5 per roll
• Spray foam: Apply polyurethane foam over the steel wool to seal. Caution: some rodents chew through foam alone — always combine with steel wool
• Metal mesh: For roof vents, install galvanized steel mesh with openings smaller than 6 mm (¼ in)
• Metal escutcheon: Around large diameter pipes (1 in+ water entrance), a metal escutcheon screwed to the wall blocks passage

Reminder: The Plumbing Code requires that openings around pipes be sealed with non-combustible material in fire-rated walls.