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How to determine source of leak underneath kitchen sink?

Getting Established

How to determine source of leak underneath kitchen sink?

Hi Bunnings community,


I was hoping you could please help me with a method to identify the source of a leak underneath my kitchen sink.


1. We recently installed a new tap. new tapnew tap

2. Since the installation, we've noticed small puddles of water (less than 30mL) after a few hours. We placed a coloured towel underneath the sink and also noticed it got damp after several hours.

3. We've reconnected the hot and cold water connections to the water source. 2.jfif3.jfif


4. To test, we let the tap run on hot and cold water for a minute each. We then checked the junctions (pictured above) as well as the body of the pipes? and the base of the tap under the sink. 4.JPG


5. The only place I could feel moisture was at the junction of the cold water pipe/tap, but it was only a couple of drops.Jhur_0-1718167991930.png


6. It is difficult to find an active leak immediately after running the tap, but when we leave a coloured towel under the sink overnight we notice the damp zone is near the wall. 




Does anyone have any suggestions on how we can approach this problem?

Is there something a plumber can do that we can't do ourselves to determine the source of the problem?


Thank you in advance for your help.


Bunnings Team Member
Bunnings Team Member

Re: How to determine source of leak underneath kitchen sink?

Hello @Jhur 


Thanks for sharing your question about the leak underneath your kitchen sink. I suggest doing a paper towel test if the leak is very slow. The technique is to wrap a paper towel on each hose and taping the edge so that it does not unravel itself. 


Leave the paper towels attached overnight and when you wake up in the morning you can check which paper towel is damp. Once you've determined which hose is leaking, I suggest trying some basic repair methods such as putting Kinetic 12mm x 10m White Standard Thread Seal and replacing the Kinetic 1 / 2" Rubber Dome Washer - 4 Pack


You'll need to repeat the test to make sure that the leak has been repaired. If you still find a slow leak occurring it might be necessary to change the hose itself. If the leak proves to be too tricky, I suggest engaging the services of a licensed plumber to give your kitchen a thorough check.  


If you need further assistance, please let me know.




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Getting Established

Re: How to determine source of leak underneath kitchen sink?

Thank you Eric. 


Such a simple but elegant way to check - really appreciate the support.

Getting Established

Re: How to determine source of leak underneath kitchen sink?

Hi Jhur,


Based on the steps you've already taken, here's a more structured approach to pinpointing the leak:

1. Check the Connections:
- Ensure that all connections to the mixer tap, including the hot and cold water lines, are tightly secured. A loose connection can often be the source of a slow leak.

2. Inspect the Cartridge:
- Since it's a new mixer tap, there's a possibility that the cartridge inside the tap is not properly seated or is defective. The cartridge controls the flow of water, and a bad connection here can cause leaks.

3. Use a Dry Tissue Test:
- Dry all areas under the sink and the tap connections completely. Then, use a dry tissue or paper towel to wipe each connection and joint one by one while the water is running. This can help identify even the smallest leaks as the tissue will show moisture immediately.

4. Food Coloring Test:
- Add a few drops of food coloring to the water and run the tap. This can help trace the exact point of the leak if the colored water appears at the leak spot.

5. Examine Seals and Washers:
- Check the seals and washers within the tap assembly. A faulty or improperly installed washer or seal can be a common cause of leaks.

6. Use PTFE Tape:
- If you find that the connections are not perfectly sealed, you can use PTFE (Teflon) tape on the threads of the connections. Wrap the PTFE tape around the threads 2-3 times before reconnecting to ensure a tight seal.

7. Professional Inspection:
- If the above steps do not reveal the source of the leak, consider having a professional plumber inspect the installation. Plumbers have specialized tools and experience to identify and fix issues that might not be apparent through basic inspection.


Additional Tips:

- Ensure Proper Alignment: Sometimes the connections might seem tight but are not aligned correctly, causing minor leaks.
- Check for Cracks or Defects: Look for any cracks or defects in the pipes or fittings that might be causing the leak.


I hope these steps help you identify and resolve the leak under your kitchen sink. Let us know how it goes, and if you need further assistance, feel free to ask!


Best Regards,


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