It is quite common for a single kitchen tap to have kitchen sink faucet leaking underneath at some point in your life, especially considering all use we give to a device of this type. Although most leaks are easy to fix, if tap is not treated immediately, even smallest leak can cost a lot of money in long run. Before moving on, you will have to determine where leak is coming from. If leak comes from base of handle, then problem is likely that some O-rings are worn out in cartridge that needs to be replaced.
Remove rings with a knife, and coat new ones with some heat-resistant plumber’s grease. However, if kitchen sink faucet leaking underneath comes from nozzle, then a completely new cartridge assembly has to be installed. With new cartridge correctly in place, you just need to adapt to old retention clip in slot on right. Take for reference how they were placed when you initially removed them to ensure a perfect fit.
Next, place bonnet on cartridge, screw assemblies down with its slide clamps, and reinstall handle. With everything back together and handle screwed in, turn on water valves to sink and verify that kitchen sink faucet leaking underneath has been fixed. Once you are sure that everything is working properly, reinstall decorative plastic cover and tap will be ready for use.