Here's a picture of what the faucet looked like before I replaced it, pictured next to its replacement part, which I found at Lowe's. ["Universal Tub Filler Spout - Chrome" by BrassCraft® Mixet® brand (SWD0447 D, Genuine Mixet Repair Part - Part #50 PK).] Cost was $11.75 + tax.
I thought perhaps this was the only source of the leak. However I still had a leak after replacing this part:
I realized I needed to replace the cartridge. Pictured on the right is the original cartridge next to its replacement part:
After searching at both Lowe's and Home Depot, I finally located the Kohler replacement cartridge at my local Ace Hardware: The Lasco Coralais Single-Lever model number is: S-331-3. The cost was $25 plus tax.
The package for the replacement cartridge offered additional help at the following website: www.lasco.net. Here are the step-by-step directions that I located for replacing the faulty cartridge:
Faucet Stem Removal
Step 1: Turn off water to house or under the sink you are working on.
Step 2: Using a screwdriver pry up and remove the button from the top of the handle.
Step 3: Remove the screw from the top of the handle.
Step 4: Pull the handle off. (Use 13-2701 Handle puller if necessary)
Shower and wide spread faucets require the removal of the flange at this point of the repair
Step 5: A Using a pair of pliers (use masking tape to protect the finish) unscrew the flange from the faucet stem body this should expose the stem assembly.
Step 6: Using an adjustable wrench or deep socket unscrew the stem bonnet from the faucet body, Or remove the cap nut from the top of the faucet body.
Step 7: Remove the stem or cartridge from the faucet body.
Cartridge Stem Repair
Step 8: Using a pair of pliers pull up to remove the cartridge assembly. (Plastic cartridges should be replaced rather than repaired)
Step 9: Pull cartridge apart by pushing down on the top of the stem.
Step 10: Using a screwdriver pull the o-rings off the stem and bonnet assemblies.
Step 11: Replace all o-rings.
Step 12: Using a pair of pliers remove the seal and spring from the faucet body.
Step 13: replace the spring then the seal. (Apply a small amount of silicon grease)
Step 14: Reinstall the cartridge.
Step 15: Tighten the cap nut over the cartridge.
Reinstall the stem or cartridge into the faucet body. Repeat process for the other stem.
Step 16: Turn on water and check for leaks.
Step 17: Replace handles and screw into stem.
Step 18: Push handle button onto handle.
The view of the area where I removed the faulty cartridge:
Here's the new cartridge ready to be installed:
Installing the cartridge is easy... just make sure the main water valve is turned off.
Be sure to use plumbing tape to make a tight seal before screwing on the next part:
Approximate total repair cost: $37 + tax