That’s a good question. First, look underneath the sink and check to be sure that the strap assembly that operates the stopper is properly adjusted, and that the nut holding the horizontal rod in the drain assembly is secure. Be sure the stopper is properly adjusted.
Note: The chrome cap on the stopper is not designed to be flush with the flange. A seal is created by the weight of the water, which pushes the rubber seal under the stopper against the flange in the sink.
If your drain stopper has been installed to be non-removable, check to see if any section of the pivot rod or strap assembly is hitting something (a bottle of cleaner, for instance) underneath the counter or sink. If that’s what’s happening, then the stopper can't drop far enough to create a seal in the sink. Depending on what is blocking the action of the pivot rod or strap, you may be able to rotate the pop-up sink stopper slightly, so that it no longer bumps against anything under the sink.
If everything seems to be adjusted properly, check the amount of silicone or putty between the flange and the sink itself. (Although a white gasket is supplied with each non-metallic pop-up to seal under the flange, if a sink has an unusually rough surface in the drain area, it may be necessary to use silicone instead of the gasket.) It is possible to determine if there is insufficient silicone or putty under the flange by using a rubber stopper to seal the drain opening only. You can also press down on the stopper to attempt a manual seal, and determine if water is leaking around the pop-up flange. If there is insufficient silicone or putty between the sink and the pop-up flange, water will leak out of the sink into the drain, even with the drain outlet fully closed.
Note: Water will not leak onto the cabinet floor; it will seep into the drain via the overflow holes in the drain body.
To remove a pop-up sink stopper that was installed as irremovable, you’re going to need to work under your sink. Put a pillow under your back, and slide on under there.
- First, remove the nut that holds the horizontal rod to the body of the pop-up stopper.
- Lift the stopper out.
- Reattach the nut that holds the horizontal rod to the pop-up body.
- Now test to see if water is leaking around the flange, by plugging your drain with a rubber stopper.
- Do not cover the outside of the drain flange.
- If the leak continues, remove the flange and apply more silicone or putty under the flange.
To remove the flange:
- Unscrew the large nut under the sink.
- Pull the flange straight up through the sink. If the flange sticks to the sink, gently pry it loose.
- Apply a fresh, uniform-round bead of silicone or putty.
- Reinstall the flange and tighten the nut under the sink.
Note: Do not rotate the flange or pop-up stopper body after re-installation. Rotation may cause the silicone or putty seal to break, which may cause leakage.
Caution: Before using plumber's putty, be sure to read the warning labels to make sure it won't stain marble or attack plastic sinks or rubber components.