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:

Clogged drains are one of the top reasons pipes under your sink start leaking. When a drain gets blocked, water flow is disrupted, and pressure builds up in the pipes. Too much pressure can weaken the pipes, eventually leading to cracks or even bursts. 

Clogs usually happen when things like oil, grease, food scraps, or non-degradable items go down the drain. These can stick to the insides of the pipes over time, creating serious blockages. 

How to Prevent It: 

  • Don’t pour oil, grease, or food scraps down the drain.  
  • Use a drain cover or strainer to catch debris. 
  • Clean your drain regularly with safe methods, like a mix of baking soda and vinegar, to break down any buildup.

Loose Connections:

Loose pipe connections are another common reason for leaks. Over time, the connections between pipes and fixtures like faucets, garbage disposals, or P-traps can loosen. This can happen due to regular use, vibrations, or poor installation, creating small gaps that let water leak out and pool under the sink. 

How to Fix It: 

  • If you spot water under the sink, check the connections. 
  • Tighten them by hand or with a wrench—but don’t overtighten, as that can cause damage.

Corroded Pipes:

What Causes Pipes To Leak Under Sink | Corroded Pipes

As pipes get older, corrosion can set in, making them weak and more likely to develop holes or cracks. Things like constant exposure to moisture, reactions with cleaning chemicals, or hard water can speed up this process. 

How to Address It: 

  • Check your pipes regularly for rust, discoloration, or flaking metal. 
  • Replace corroded pipes before the leaks get worse. 
  • If your plumbing system is old, consider upgrading to corrosion-resistant materials like PVC or stainless steel.

Faulty Seals:

Worn-out seals are another big cause of leaks, especially around the base of the faucet or where pipes connect to other fixtures. Over time, seals can crack, wear out, or get damaged, allowing water to seep through. 

What You Can Do: 

  • If you see water dripping or pooling around the faucet base, it’s probably a bad seal. 
  • Swap out the old seal or rubber gasket for a new one to stop the leak.

High Water Pressure:

Everyone likes good water pressure, but if it’s too high, it can put extra strain on your pipes and joints. Over time, this stress can cause cracks, bursts, or leaks. 

How to Manage It: 

  • If you think your water pressure is too high, use a water pressure gauge to check it. A safe range is usually between 40 and 60 PSI. 
  • Install a pressure regulator if needed to keep water pressure at safe levels and protect your pipes.

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