Patedepollo

Plumbing fixtures demand more repairs than pipes. Take pop-up sink stoppers. Even slightly out of adjustment, they leak. You can buy a rubber plug more easily than repair the stopper. Measure across the mouth of the open drain, and buy a plug to fit. However, that’s not the real answer.
Pop-up drain stoppers incur several problems. They become clogged with hair, rods warp or come loose, and the stopper gets bent so the drain won’t seal. To make repairs, first lift the stopper itself upward and twist to release it. Scrape off or untangle any collected debris. Clean the drain with a strong cleaner such as Drano. Scrape the stopper lip, and the drain edge where it fits, with fine steel wool.
Reverse the removal steps to replace the stopper. Try the stopper handle. If the stopper still doesn’t seal, pull it out, rotate it a half-turn, and reseat it.
For persistent leaking, get under the fixture. With a wrench, tighten. the stopper-lever assembly where it connects to the drain. If it’s corroded, clean it. Reseal it with new pipe dope if the old dope looks rotten; otherwise, leaks occur at the trap.
One arm of the lever assembly has either several notches or a threaded adjustment. Slip the arm rod into another notch (or turn the adjustment) until you find a position that seals the drain. Take out a bent plunger by backing out the screw that locks it into the assembly. Try a plumbing-supply shop for a replacement.
Lubricate the shaft of a balky plunger with silicone spray. That might free it up enough that it can seal properly and keep water in the sink (for at least a half-hour).