How To Install Bathroom Sink Drain/Faucet, No Leaks Under Gasket, Threads [SOLVED] 2025

Your host Jeff Ostroff shows you the correct way to install a bathroom sink drain and faucet without getting that annoying leak underneath the bathroom sink, with water dripping down the threaded drain pipe and out the black rubber gasket. This bathroom sink drain leaking underneath affects a lot of people who otherwise installed their bathroom drain according to the drain manufacturer's instructions. You'll avoid bathroom sink drain leaking threads forever.

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Table of Contents (Click to jump to any chapter)
0:00 Introduction of bathroom sink leaking underneath gasket problem
0:34 Anatomy of Threaded Drain Pipe, Causes of Leaks
2:30 Solution to Problem Installing Sink Drain with No Leaks
4:30 Wrapping Plumber's Teflon Tape Around Bathroom Drain Threads
6:50 Installing Drain Flange and Threaded Drain Pipe
10:08 Installing Bathroom Sink Faucet
11:20 Installing Bathroom Faucet Stopper, Lift Rod Assembly
12:15 Removing Bathroom Sink Aerator, Flushing Faucet
12:35 Water Testing Bathroom Faucet, Drain For Leaks
13:15 Checking Downward Slop of P-Trap Arm Into Waste Pipe
13:35 More Leak Testing Hot Water, Overflow, Overnight Drips
14:45 Discussion: Plumber's Putty Not Recommended On Drain Gasket

📺 WATCH: How To Install Kitchen Faucets: DIY Plumbing Tips: https://youtu.be/1oz-PvAW1Fc
📺 WATCH: How To Fix Bathroom Sink Drain Leaks Underneath Gasket, Threads [SOLVED]: https://youtu.be/NkWS8vnUA4s
📺 WATCH: Why is my Kitchen Sink P-Trap Leaking at Connection Nut?: https://youtu.be/cEjiICErSQg
📺 WATCH: How to Replace A Kitchen Sink Drain Strainer, Repair Leak: https://youtu.be/nBlyqU7NJJI
📺 WATCH: How To Fix Leaking Shut Off Valve FAST DIY - Avoid Plumber: https://youtu.be/7LH5eUmx2HI
📺 WATCH: 4 Plumbing Parts/Tools You Should NEVER Use. https://youtu.be/hpP36QTjNNU​
📺 WATCH: How To Repair/Replace Leaking P-Trap Pipe Under Bathroom Sink: https://youtu.be/NkWS8vnUA4s​
📺 WATCH: How to Install P Trap Under Bathroom Sink, Drain Pipe Off Center: https://youtu.be/b_OSgwpteR4
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Should your leaking drain repair use plumber's putty to avoid staining the bathroom vanity sink. We'll also cover Teflon tape (plumber's tape), pipe dope sealant, and silicone to fix the bathroom sink drain.

The lower Teflon tape for the black bathroom drain gasket should be wrapped counter clockwise, to match direction of the drain gasket screwing upward from underneath the leaking sink basin. The upper Teflon tape should wrap clockwise around threads of the leaking drain pipe to match the direction of the drain flange inside the sink, screwing downward onto the pipe threads in a clockwise motion.

You still have to fill up the sink basin with water until it starts to drain out through the overflow hole, then you also need to let the water suddenly all drain out. You have been moving a lot of parts underneath your bathroom vanity sink, so make sure to test for the sink trap leaking as well. If the sink trap is leaking, we add pipe thread sealant to the leaking trap connection.

Causes of your bathroom sink drain leaking underneath

If the drain hole in the sink has imperfections preventing the gasket from mating to the sink for a perfect seal. Some people have issues installing Moen faucet systems with Moen drains and they have a leak. Drain leaks happen with Glacier Bay as well, the leaking vanity drain is allowing water to leak down the threads of the drain pipe under the vanity sink. It is one root cause of your bathroom sink leaking from the drain gasket.

The drain repair solution for this vanity sink leaking issue is to wrap plumber's tape around the top of the pipe threads where the drain flange will screw on. Wrap tape on pipe threads where rubber drain gasket mates to the bottom of the basin underneath the vanity.