Small Pin Holes in Sink Plumbing? It Could Be Pests!

You just noticed tiny pin-sized holes near your kitchen or bathroom sink—and your first thought is, “Did something chew through my pipes?” You’re not alone. Homeowners across the U.S. report mysterious small pin holes found in sink plumbing pests, often after noticing strange odors, slow drains, or even tiny insects crawling near fixtures. These holes aren’t random wear—they’re frequently caused by pests seeking moisture, warmth, or shelter. In this guide, we’ll help you identify the culprits, assess the damage, and take fast, effective action to protect your home’s plumbing and health.

What Causes Small Pin Holes in Sink Plumbing?

Many assume pinhole leaks or holes are due to corrosion or poor pipe quality—but pest activity is a surprisingly common cause, especially in homes with PVC, ABS, or older copper pipes. Rodents like mice and rats can gnaw through softer plumbing materials, while certain insects may bore into seals or gaskets.

According to the National Pest Management Association (NPMA), 29% of homeowners report rodent damage to plumbing or wiring—often beginning with tiny entry points near sinks or under cabinets. These pests are drawn to the constant moisture and dark, enclosed spaces under sinks.

“Mice can squeeze through openings as small as a dime—and their teeth grow continuously, so they must gnaw to keep them worn down,” explains Dr. Emily Snyder, entomologist and pest control consultant.

Which Pests Are Likely Creating These Pin Holes?

Not all pests can chew through pipes—but several common household invaders can cause or contribute to small pin holes found in sink plumbing pests:

1. House Mice (Mus musculus)

• Behavior: Gnaw constantly to control tooth length.
• Damage: Can chew through PVC, rubber gaskets, and even thin copper.
• Signs: Droppings, greasy rub marks, faint scratching sounds at night.

2. Norway Rats (Rattus norvegicus)

• Behavior: Stronger jaws than mice; target water sources.
• Damage: Capable of chewing through thicker plastic and soft metal pipes.
• Signs: Larger droppings, burrows near foundations, strong ammonia odor.

3. Drain Flies (a.k.a. Moth Flies)

• Note: They don’t chew holes—but their presence indicates organic buildup that can degrade pipe seals, creating gaps that look like pin holes.
• Signs: Tiny fuzzy flies hovering near drains; larvae in slimy pipe residue.

4. Termites (Less Common, But Possible)

• Risk: Subterranean termites may tunnel through wood near plumbing, sometimes reaching pipe insulation or supports.
• Signs: Mud tubes, hollow-sounding wood, discarded wings.

📌 Important: While insects like drain flies don’t create structural holes, their activity can accelerate pipe deterioration—leading to leaks that mimic pest-chewed damage.

How to Confirm If Pests Are Behind the Pin Holes

Before calling a plumber, rule out pest involvement with this 5-step check:

1. Inspect Under the Sink (Use a Flashlight)
   Look for chew marks, droppings, nesting materials (shredded paper, insulation), or oily smudges on pipes.
2. Check for Live Pests
   Set non-toxic glue traps near pipes overnight. Mice often travel the same paths repeatedly.
3. Examine Pipe Material
   PVC and ABS pipes with clean, sharp-edged holes suggest gnawing. Corrosion-related pinholes on copper pipes usually look pitted or greenish.
4. Smell for Ammonia or Mustiness
   Rodent urine has a sharp ammonia odor. Drain flies emit a faintly sweet, decaying smell.
5. Monitor Water Pressure & Leaks
   If leaks coincide with new holes and worsen at night, pests are likely active.

For visual reference, the U.S. Environmental Protection Agency (EPA) and university extension services confirm that gnaw marks near plumbing are a top indicator of rodent infestation.

Step-by-Step: How to Fix and Prevent Pest-Caused Pin Holes

Step 1: Eliminate the Pest Infestation

• For mice/rats: Use snap traps or electronic traps baited with peanut butter. Place them along walls near the sink cabinet.
• For drain flies: Pour 2 liters of boiling water down the drain daily for 3 days. Then, mix ½ cup baking soda + ½ cup vinegar, let sit 30 minutes, and flush with hot water.
• Severe cases: Contact a licensed pest control professional. The NPMA recommends quarterly inspections for homes in high-risk areas.

Step 2: Repair Damaged Plumbing

• Minor pipe damage: Use epoxy pipe repair putty (e.g., JB Weld Waterweld). Clean and dry the area, knead the putty, and apply over the hole. Cures in 15–25 minutes.
• Severe damage: Replace the affected pipe section. Use metal mesh shielding around new pipes to deter future gnawing.

Step 3: Seal All Entry Points

• Use steel wool + expanding foam (like Great Stuff Pestblock) to seal gaps around pipes where they enter walls or floors.
• Ensure sink cabinets have tight-fitting doors with no gaps at the bottom.

Step 4: Reduce Moisture & Attractants

• Fix leaky faucets immediately—standing water attracts pests.
• Store pet food and trash in sealed containers away from the kitchen sink.
• Run exhaust fans during and after showers to reduce humidity.

💡 Pro Tip: Install under-sink motion LED lights. Pests avoid well-lit areas, and you’ll spot activity faster.

Comparison: Pest Damage vs. Corrosion in Sink Pipes

Why Ignoring These Holes Is Risky

Small holes may seem harmless—but they can lead to:

• Structural water damage (costing $3,000–$10,000 on average to repair, per HomeAdvisor)
• Mold growth within 24–48 hours of moisture exposure
• Electrical hazards if water reaches nearby outlets
• Secondary infestations (e.g., ants attracted to moisture)

Early intervention saves thousands—and protects your family’s health.

FAQ Section

Q1: Can insects really chew through metal or plastic pipes?

Most insects (like drain flies or silverfish) cannot chew through solid pipes. However, rodents like mice and rats can easily gnaw through PVC, rubber, and thin copper. Insects may exploit existing cracks or degrade seals, creating leak-like openings.

Q2: Are pinhole leaks always caused by pests?

No. Pinhole leaks in copper pipes are often due to pitting corrosion from water chemistry (e.g., high chlorine or low pH). But if you see clean, round holes with nearby droppings or gnaw marks, pests are the likely cause.

Q3: How quickly can mice damage plumbing?

A single mouse can create visible damage in as little as 48 hours. Their teeth grow 5 inches per year, forcing constant gnawing—on pipes, wires, and cabinetry.

Q4: What’s the best way to inspect under the sink safely?

Turn off water supply valves first. Use a headlamp or phone light, wear gloves, and avoid reaching blindly. Look for droppings (mouse: rice-sized; rat: capsule-shaped) and fresh chew marks (light-colored, not weathered).

Q5: Can I prevent this without using poison?

Absolutely. Focus on exclusion and sanitation: seal entry points with steel wool, eliminate food/water sources, and use humane traps. Avoid rodenticides—they can cause dead pests to decay in walls, creating odors and attracting secondary pests.

Q6: When should I call a professional?

Call a plumber and pest control expert if:

• You see multiple holes or active pests
• There’s standing water or mold under the sink
• DIY traps and repairs don’t resolve the issue within 1 week

Conclusion

Finding small pin holes found in sink plumbing pests is a red flag—not just for leaks, but for a hidden infestation that could cost you thousands if ignored. By identifying the pest, repairing damage, and sealing entry points, you protect your home’s integrity and your family’s well-being.

Don’t wait for a flooded kitchen or a full-blown infestation. Take action today—inspect, clean, and seal. And if this guide helped you, share it with a friend or neighbor! A quick post on Facebook or Pinterest could save someone from a plumbing nightmare.

🔧 Your home deserves peace of mind—starting from the pipes up.