What Can Cause a Leak Under the Bathroom Sink?

Discovering a leak under your bathroom sink can be a worrying sign of potential water damage. Common in many Australian homes, a leaking bathroom sink can lead to further issues if not addressed promptly.
Whether it’s a dripping pipe, a faulty sink drain, or loose connections, understanding the cause is crucial for effective repair.
When a bathroom sink leaks, it can result from various plumbing issues such as a worn-out seal, a leaking pipe, or loose connections. Fixing these problems with the right tools like a pipe wrench or plumber’s tape can prevent water damage and costly repairs. Regular maintenance and inspections are key to avoiding these plumbing headaches.
Common Causes of Leaks Under the Bathroom Sink
Here are the usual suspects when you’re experiencing a bathroom sink leak:
- Loose or worn-out connections: One common cause of a leak under the bathroom sink is loose or worn-out connections. Over time, slip nuts and washers can become loose, leading to water seeping through. An adjustable wrench can be used to tighten connections and ensure a watertight seal. Regularly checking and tightening these connections can prevent leaks from developing.
- Faulty sink drain: A faulty drain pipe or drain assembly is another typical culprit for a bathroom sink leaking underneath. If the drain assembly is not properly sealed with plumber’s putty, water can leak through the sink basin. Excess putty can also cause issues. Ensuring the drain assembly is correctly installed and replacing worn-out parts can fix this issue.
- Damaged sealant or caulking: Damaged sealant or caulking around the sink bowl can allow water to drip into the cabinet below. Over time, the sealant can deteriorate due to constant exposure to water. Reapplying plumber’s putty or caulking can help create a watertight seal. If the leak persists, it may be best to seek professional assistance to prevent further damage.
Identifying the Source of the Leak
There are any number of causes, so how do work out the source of the leak? Let’s take a look:
- Visual inspection: To identify the source of a leak under the bathroom sink, start with a visual inspection. Look for obvious signs of water leaking from supply lines, the P trap, or the shut-off valves. Check for rust, corrosion, or water stains on the floor and walls beneath the sink. Ensure all components, like the retaining nut and O-ring, are intact and not worn out.
- Test different components: Testing different components can help pinpoint the leak. Turn off the water supply using the shut-off valves, then dry the area with paper towels. Turn the water back on and observe for leaks around the supply lines, P trap, and other fittings. If water starts seeping at any point, you’ve found the problem area. Tightening connections or replacing worn parts may be necessary.
- Use tissue or paper towels: A simple method to detect leaks is to use tissue or paper towels around suspected areas. This can highlight small drips and pinpoint exact locations where water is coming from. If the leak persists despite DIY repair efforts, consider calling a professional plumber. Ignoring a leak can lead to significant property damage and costly repairs, so it’s essential to address the issue promptly.
Leaking Pipes and Joints
How do you tackle the various causes? Let’s start with leaking pipes and joints:
- Corroded pipes: Corroded pipes are a common cause of a leak under the bathroom sink. Over time, pipes can rust and degrade, leading to leaks. This is particularly common in older houses where plumbing systems have not been updated. Regularly inspecting pipes for signs of corrosion and replacing them can prevent water from seeping through and causing further damage to walls and floors.
- Loose pipe connections: Loose pipe connections can also result in leaks. Ensuring that all connections are properly tightened can stop water from escaping. Use a wrench to tighten screws and joints, and check the washers for wear. If the leak persists, it may be necessary to replace the washers or the entire pipe segment to ensure a secure and watertight fit.
- Cracked or damaged pipes: Cracked or damaged pipes can cause water to flow uncontrollably, leading to a significant leak. P traps, designed to hold water and prevent sewer gases from entering the house, are particularly susceptible to damage. If you notice water coming from a crack, it’s crucial to replace the damaged section promptly. Using a bucket to catch dripping water can prevent immediate damage while you prepare for a more permanent fix. For severe cases, consider seeking professional assistance to ensure proper repair and avoid further complications.
Sink Drain Issues
Problems with the sink drain are a common sign of bathroom sink leaks:
- Clogged sink drain: A clogged sink drain can lead to a leak under the bathroom sink. When water pressure builds up behind a blockage, it can force water to seep through joints and seals. Regularly cleaning the drain and using a quarter turn to clear minor clogs can prevent water from backing up. This is a common issue not only in the bathroom but also in the kitchen sink.
- Worn-out drain gasket: A worn-out drain gasket is another frequent cause of leaks. The gasket creates a seal between the sink and the drain assembly. Over time, this gasket can deteriorate, leading to leaks. Inspect the gasket for wear and tear and replace it if necessary. Ensure the drain assembly is tightly secured with a screw to maintain a watertight seal.
- Improper installation: Improper installation of the sink drain can also result in leaks. If the drain assembly is not properly aligned or tightened, water can seep through. Make sure all components are correctly installed and secured. Tighten any loose screws and ensure the washer is in good condition. If the issue persists, it might be necessary to fill any gaps with plumber’s putty to ensure a proper seal against the wall of the sink.
Problems with Sealants and Caulking
This is another common cause of bathroom sink leaks.
- Deteriorated caulking: Deteriorated caulking around the sink can lead to a leak under the bathroom sink. Over time, caulking can crack and shrink, allowing water to seep through gaps between the sink and the countertop. Regularly inspect the caulking and replace it if you notice any signs of wear. Removing old caulking and applying a fresh bead can help maintain a watertight seal and prevent leaks.
- Improper application of sealant: Improper application of sealant can also cause leaks. If the sealant is not applied evenly or if there are gaps, water can find its way through. Make sure to apply sealant smoothly and evenly, pressing it firmly into place to ensure a good seal. Using the right type of sealant for your sink material is crucial to achieving a long-lasting bond.
- Reapplying sealant or caulking: When reapplying sealant or caulking, it’s important to clean the area thoroughly. Remove any old caulk or sealant and dry the surface completely before applying new material. This ensures that the new sealant adheres properly and forms a watertight barrier. If the problem persists despite reapplication, it might be wise to seek professional assistance to avoid further water damage and ensure a proper fix.
Tap Leaks
Could it be your taps causing the problem?
- Leaking tap base: A leaking tap base is a common issue that can cause a leak under the bathroom sink. Water can seep through if the base is not tightly sealed, leading to drips and puddles. Regularly check the tap base and ensure it is securely attached. Tightening any loose screws can help maintain a watertight seal and prevent leaks.
- Faulty O-rings or washers: Faulty O-rings or washers are another common cause of leaks in taps. These small components can wear out over time, leading to water leaks. If you notice water leaking from the tap, it may be time to replace the O-rings or washers. Ensure you have the correct size and type for your specific tap model to ensure a proper fit and prevent further leaks.
- Loose or damaged tap components: Loose or damaged tap components can also result in leaks. Check all parts of the tap, including handles and spouts, for any signs of damage or wear. Tighten any loose parts and replace any damaged components. Regular maintenance and timely repairs can prevent small issues from becoming major problems, ensuring your tap operates smoothly and without leaks.
Ensure Your Bathroom Sink is Leak Free Today
Addressing a leak under the bathroom sink promptly is crucial to prevent further water damage and costly repairs. By identifying common causes such as loose connections, faulty sink drains, and deteriorated sealants, you can take the necessary steps to fix these issues effectively.
Regular maintenance and inspections can help prevent bathroom sink leaks. If you encounter persistent leaks despite DIY repairs, seeking professional assistance is advisable. A professional plumber can ensure that all plumbing components are properly installed and functioning, providing peace of mind and a leak-free bathroom.
Please note: This information is provided for advice purposes only. Regulations differ from state to state, so please consult your local authorities or an industry professional before proceeding with any work. See our Terms & Conditions here.