What Causes Pipes To Leak Under Sink

A leaking pipe under your kitchen or bathroom sink can be a real headache. It’s not just inconvenient—it can cause costly water damage, raise your bills, and disrupt water pressure. Knowing what causes these leaks can help you stay ahead and fix the problem quickly. 

This blog covers what causes pipes to leak under sinks and practical tips to fix them.

Why Pipes Leak Under the Sink

There are plenty of reasons why the pipes under your sink might spring a leak. Let’s break down the most common causes and how they lead to trouble.

Clogged Drains:

Drain Trap - Causes of Pipe Leaks Under Sink

Clogged drains are one of the top reasons pipes under your sink start leaking. When a drain gets blocked, water flow is disrupted, causing pressure to build up in the pipes. Over time, this buildup of pressure can weaken the pipes, leading to cracks or even bursts. Left unchecked, a clog can cause significant water damage and costly repairs. 

Clogs usually occur when substances like oil, grease, food scraps, or non-degradable items such as wipes or hygiene products are sent down the drain. These materials can stick to the insides of the pipes, gradually creating serious blockages that restrict water flow and increase pressure further. Blockages often develop in the drain trap section of your plumbing system. Once the problem starts, it tends to worsen if not addressed quickly.

How to Prevent It: 

  • Avoid pouring oil, grease, or food scraps down the drain, as these are the leading causes of buildup. 
  • Install a drain cover or strainer to catch debris before it enters the pipes. These inexpensive tools can prevent major plumbing issues. 
  • Clean your drain regularly using safe and natural methods, like a combination of baking soda and vinegar, to help dissolve buildup. For tougher clogs, consider using a drain snake or seeking professional assistance. 

Loose Connections:

Loose pipe connections are another common culprit behind leaks. Over time, the connections between pipes and fixtures like faucets, garbage disposals, or P-traps can loosen. This typically happens due to regular use, vibrations caused by appliances, or poor installation practices. Even a small gap in these connections can allow water to escape, leading to leaks that may pool under the sink and cause unseen damage. 

Loose connections can also lead to a gradual weakening of the surrounding areas, especially if leaks are left unnoticed for long periods. This might even result in mold growth, which can pose health risks. 

How to Fix It: 

  • If you notice water pooling under the sink, inspect the pipe connections carefully. Look for signs of water dripping or dampness around connection points. 
  • Tighten these connections by hand or using a wrench. Be cautious not to overtighten, as this can strip threads or damage gaskets, worsening the issue. 
  • If the problem persists, check for worn gaskets or seals at the connections and replace them as needed. 

Corroded Pipes:

What Causes Pipes to Leak Under Sink | Corroded Pipes

As pipes age, they are prone to corrosion, which weakens the material and makes them more likely to develop holes or cracks. Corrosion is often caused by constant exposure to moisture, reactions with certain cleaning chemicals, or hard water that contains high levels of minerals. Over time, this can lead to leaks that start small but can escalate into bigger problems. 

Rust, discoloration, or flaking on the pipes are early signs of corrosion. Corroded pipes not only leak but may also affect water quality, introducing rust particles into the water supply. If ignored, this can lead to a full pipe failure, resulting in extensive water damage and costly repairs. 

How to Address It: 

  • Regularly inspect your pipes for visible signs of rust, discoloration, or flaking metal. Early detection can prevent more serious issues. 
  • Replace corroded pipes as soon as possible before leaks worsen and cause structural damage to your home. 
  • If your plumbing system is old, consider upgrading to more durable, corrosion-resistant materials like PVC, PEX, or stainless steel. These materials are designed to withstand harsh conditions and last longer.

Faulty Seals:

Plumber Skill - Hard Skills

Worn-out seals are another major cause of leaks, particularly around the base of faucets or where pipes connect to fixtures. Seals, often made of rubber or silicone, degrade over time due to constant exposure to water, temperature changes, and regular wear and tear. Once a seal cracks, wears out, or becomes damaged, water begins to seep through these areas, leading to dripping or pooling. 

Faulty seals not only waste water but can also create damp conditions that encourage the growth of mold and mildew. This can affect air quality and cause respiratory issues if not addressed. 

What You Can Do: 

  • Check for water dripping or pooling around the faucet base or where pipes connect to fixtures. If you notice these signs, a worn-out seal is likely the cause. 
  • Remove the old seal or rubber gasket and replace it with a new one. Make sure to select the correct size and material for a proper fit. 
  • For added durability, consider using high-quality seals or applying a waterproof silicone sealant to reinforce the connection. 

High Water Pressure:

Good water pressure makes daily tasks like washing dishes or showering more enjoyable, but excessively high water pressure can put undue strain on your plumbing system. Over time, this extra pressure can weaken joints, damage seals, and even cause pipes to crack or burst. 

High water pressure also accelerates wear and tear on appliances like dishwashers and washing machines, reducing their lifespan. Signs of excessive water pressure include loud banging noises (water hammer) or frequent leaks in your plumbing system. 

How to Manage It: 

  • Use a water pressure gauge to check the pressure in your home. The safe range is usually between 40 and 60 PSI, depending on your plumbing system. If the pressure is too high, it can lead to significant damage over time. 
  • Install a pressure regulator to keep water pressure within a safe range. These devices are affordable and can save you from expensive repairs. 
  • Regularly monitor your water pressure and watch for signs of strain on your plumbing, such as leaks or unusual noises, to address issues early. 

By staying on top of these common causes of leaks, you can save yourself from costly repairs and ensure your plumbing system stays in great shape for years to come.

Prevention and Fixing the Issue

The easiest way to avoid leaks under your sink is with regular maintenance and catching small problems early. Here are some simple tips to help you stay ahead of the game: 

  1. Check Your Pipes Regularly: Every few weeks, take a quick peek under the sink and around any exposed pipes to make sure everything’s in good shape. Keep an eye out for damage, rust, loose connections, discoloration, water stains, or even a funky, musty smell—these can all be early warning signs. Catching small issues early can save you from expensive repairs or a major water disaster later on. 
  2. Keep Drain Pipes Clear: Don’t pour grease, oil, coffee grounds, or anything that doesn’t break down naturally down your drains. These things can build up and cause annoying clogs. Use strainers in sinks and showers to catch stuff like hair, food bits, or other debris, and clean them out regularly. Once a month, try using a natural solution like baking soda and vinegar to keep your drains flowing smoothly. 
  3. Tighten Loose Connections: If you notice water pooling under the sink or hear that constant dripping sound, check your pipe connections ASAP. Sometimes it’s as simple as tightening a loose fitting with a wrench. If tightening doesn’t fix it, there might be a bigger issue like worn threads or damaged pipes, which might call for a pro to step in. 
  4. Replace Old Seals: Noticing water around the base of your faucet, sink, or other fixtures? That’s usually a sign of worn-out seals or gaskets. These wear down over time and can lead to leaks if left alone. Luckily, replacing them is typically an easy and inexpensive fix—just don’t forget to use the shut off valves to turn off the water supply before you start! 
  5. Keep an Eye on Water Pressure: Sure, high water pressure feels awesome in the shower, but it can stress out your pipes and fixtures, leading to leaks or even bursts over time. Use a water pressure gauge to check your levels (ideally between 40-60 PSI). If it’s too high, installing a pressure regulator can help protect your pipes and keep your plumbing in good shape.

The Bottom Line – Know What Causes Pipes to Leak Under Sink

A leaky pipe under the sink can turn into a much bigger problem if you ignore it. Whether it’s clogged drains, loose connections, rusted pipes, damaged seals, or high water pressure, figuring out the cause is key to fixing it. 

If you’re facing leaks, corrosion, or tough plumbing problems, it’s time to call a plumber. If you’re in Sacramento and need a professional plumber, don’t hesitate to reach out to a trusted Sacramento plumber like Fix-It Rite. Fixing leaks early can save you money, protect your home, and prevent bigger repairs later.

Posted in Plumbing Tips