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Drainage & LeaksKitchen PlumbingPlumbingJanuary 08, 2023
Finding a Leak Under the Kitchen Sink
Have you ever opened the cabinet under your kitchen sink to find a soggy mess? Now, you have the unpleasant job of pulling wet cleaning supplies out of the cabinet and mopping everything up. Then, you still may not know the cause of the leak.
If it’s a big leak, it’s usually easy to spot. You will see corroded pipes or other obvious signs. If the leak is tiny, it may be harder to find. One small leak can get everything wet in a hurry.
As a homeowner, you may find this frustrating, but we see this problem frequently. We recommend the following system to test various parts of your kitchen sink’s plumbing setup to find the leak. Once you find the problem, you can determine the options for fixing it.
Be sure to dry everything in the cabinet thoroughly, including the drainpipes, water supply lines, garbage disposal, shut-off valves, etc. Mop up the excess water on the cabinet's floor, too.
While drying everything, you may see water returning right after you dry it away. If so, you have found the leak.
Start at the place where the pipes and/or disposal attach to the sink(s). Watch closely to see if this area leaks. You may need to feel the area with your fingers to detect moisture more easily at the leaking spot.
Still don’t see the leak? The next step is to start the dishwasher. Let it run for several minutes so it can fill with water. Then, manually stop the cycle and drain the dishwasher. (This is typically achieved by pushing the “cancel/drain” button, but your dishwasher may differ.) Most dishwashers drain into the side of the garbage disposal, near the top, through a white or black pipe. You ought to hear a water-draining or trickling sound. Some dishwashers drain through an “air gap” device on the countertop near the faucet. Check there also.
If the source of the leak is still a mystery, the next step is to grab your flashlight, check the faucet supply lines, and shut off the valves again. You could have missed a small leak when examining these areas. Signs of rust or white mineral deposits on the supply/valve hardware are signs that might indicate there is a tiny leak.
Test the faucet robustly, just as you tested the drainpipes. Turn it on and off several times, moving the handle every way it goes. Move the spout as well simultaneously. Test the sprayer several times, pulling it out and testing its functions. With each new test, keep looking for new puddles or drips under the cabinet. Some faucets only leak when put in a certain position or operated in one certain way.
You can protect your cabinet by placing several baking sheets or shallow containers under the potential leak points under your sink. You can also buy metal or rubber cabinet liners to protect the under-sink cabinet from undetected leaks.
You can return everything where it was and use your sink as you would otherwise. Check it periodically, especially after you have used it heavily. If you find water again, you can repeat the process described above. Your pans under the sink will protect your cabinet from damage and may even help you determine the location of the leak.
You may wish to consider getting a water alarm. These battery-powered devices sound an alarm when their sensors detect moisture. Some water alarms are Wi-Fi enabled and come with an app that can notify your smartphone when a leak is detected. These devices are useful in the kitchen sink and the water heater drain pan.
If it’s a big leak, it’s usually easy to spot. You will see corroded pipes or other obvious signs. If the leak is tiny, it may be harder to find. One small leak can get everything wet in a hurry.
As a homeowner, you may find this frustrating, but we see this problem frequently. We recommend the following system to test various parts of your kitchen sink’s plumbing setup to find the leak. Once you find the problem, you can determine the options for fixing it.
Establishing A Baseline
The first step to find a leak is to prepare the work area and establish a baseline. Preparation means removing everything in the cabinet where the leak is. To see under the sink and find the leak, you will probably need to lie down on your back inside the cabinet. Gather some old towels and grab a flashlight.Be sure to dry everything in the cabinet thoroughly, including the drainpipes, water supply lines, garbage disposal, shut-off valves, etc. Mop up the excess water on the cabinet's floor, too.
While drying everything, you may see water returning right after you dry it away. If so, you have found the leak.
The Flow Test
If you still haven’t found the leak after drying, you will need to test the drainpipes systematically. Most of the time, drainpipe leaks come from a drain line with a loose slip-joint connection. You will need to turn on the water to see the leaking drainpipe. Run the water in each basin for a few minutes and look under the sink with your flashlight for a leak.Start at the place where the pipes and/or disposal attach to the sink(s). Watch closely to see if this area leaks. You may need to feel the area with your fingers to detect moisture more easily at the leaking spot.
The Basin Test
If the flow test did not uncover the leak, try a stress test on the drainpipes. Stop up each basin and add water. This is called the “basin test.” When the basins are full, remove both stoppers and let them drain, then flip on the garbage disposer. All drainpipes are now under the most stress they will receive during normal usage. Keep watching the drainpipes and garbage disposal under the sink while the basins are draining and the disposer is on to look for the leak.Still don’t see the leak? The next step is to start the dishwasher. Let it run for several minutes so it can fill with water. Then, manually stop the cycle and drain the dishwasher. (This is typically achieved by pushing the “cancel/drain” button, but your dishwasher may differ.) Most dishwashers drain into the side of the garbage disposal, near the top, through a white or black pipe. You ought to hear a water-draining or trickling sound. Some dishwashers drain through an “air gap” device on the countertop near the faucet. Check there also.
The Faucet Stress Test
If the source of the leak is still a mystery, the next step is to grab your flashlight, check the faucet supply lines, and shut off the valves again. You could have missed a small leak when examining these areas. Signs of rust or white mineral deposits on the supply/valve hardware are signs that might indicate there is a tiny leak.Test the faucet robustly, just as you tested the drainpipes. Turn it on and off several times, moving the handle every way it goes. Move the spout as well simultaneously. Test the sprayer several times, pulling it out and testing its functions. With each new test, keep looking for new puddles or drips under the cabinet. Some faucets only leak when put in a certain position or operated in one certain way.
What’s Next?
If you still have not been able to diagnose the leak, you may have an intermittent leak. In this case, it is better to continue to watch the under-sink plumbing for a little while rather than take a guess at what is leaking and waste money if you guess wrong.You can protect your cabinet by placing several baking sheets or shallow containers under the potential leak points under your sink. You can also buy metal or rubber cabinet liners to protect the under-sink cabinet from undetected leaks.
You can return everything where it was and use your sink as you would otherwise. Check it periodically, especially after you have used it heavily. If you find water again, you can repeat the process described above. Your pans under the sink will protect your cabinet from damage and may even help you determine the location of the leak.
You may wish to consider getting a water alarm. These battery-powered devices sound an alarm when their sensors detect moisture. Some water alarms are Wi-Fi enabled and come with an app that can notify your smartphone when a leak is detected. These devices are useful in the kitchen sink and the water heater drain pan.
Conclusion
This process should help you find a leak under your kitchen sink. If you cannot find the leak under your sink after many tries, call us. Our licensed plumbers have years of experience finding elusive leaks and have all the tools and materials needed to fix the leak, whether it is a supply line, a valve, a drain, a faucet, or a garbage disposal. Find a location near you to schedule your next plumbing service.
