1. High-quality faucets come with flexible plastic gaskets that create a durable watertight seal at the bottom of the faucet, where it meets the sink deck. However, an inexpensive faucet may have a flimsy-looking foam seal that doesn’t do a good job of sealing and disintegrates after a few years. If that is the case with your faucet, discard the seal and press a ring of plumber’s putty into the sealant groove on the underside of the faucet body.
2. Insert the faucet tailpieces through the holes in the sink. From below, thread washers and mounting nuts over the tailpieces, then tighten the mounting nuts with a basin wrench until snug. Put a dab of pipe joint compound on the threads of the stop valves and thread the metal nuts of the flexible supply risers to these. Wrench tighten about a half-turn past hand tight. Overtightening these nuts will strip the threads. Now tighten the coupling nuts to the faucet tailpieces with a basin wrench.
3. Slide the lift rod of the new faucet into its hole behind the spout. Thread it into the clevis past the clevis screw. Push the pivot rod all the way down so the stopper is open. With the lift rod also all the way down, tighten the clevis to the lift rod.
4. Grease the fluted valve stems with faucet grease, then put the handles in place. Tighten the handle screws firmly, so they won’t come loose during operation. Cover each handle screw with the appropriate index cap – Hot or Cold.
5. Unscrew the aerator from the end of the spout. Turn the hot and cold water taps on full. Turn the water back on at the stop valves and flush out the faucet for a couple of minutes before turning off the water at the faucet. Check the riser connections for drips. Tighten a compression nut only until the drip stops. Replace the aerator.