The supply lines leading to the kitchen sink, both the hot and cold, begin at a water supply valve and end at the tap supply tubing that is attached to the faucet. The connections are all screw-on kinds, either hand-tightening nuts or even compression nuts, and in most cases this is where the problem lies. Virtually every contemporary kitchen sink supply line is really a do-it-yourself task, so repairing a leaky provide line is only going to require the use of tools that may be seen in every home toolbox.
Find the leak. Unless the leak is obvious — such as water squirting out from a connection or noticeably dripping off of a source valve — you will have to find it. Wipe down the supply line with a dry rag to remove all the moisture. Wrap toilet paper across the supply line beginning at the connections and the supply valve. Toilet paper will show wetness quickly, and you will be able to determine just where the leak emanates from by watching where the toilet paper gets wet.
Tighten the connections where the supply line attaches if it’s leaking there. Twist a hand-tightening nut a quarter run, or flip a compression nut a quarter turn using an adjustable wrench. In many cases the leak will stop after this is completed. If not, move on to Step 3.
Switch off the water at the source valve, which can be found under the sink. Eliminate the hand-tightening nut and then spread some plumber’s pipe compound onto the threads along with the drier inside the fitting. Tighten it down again, hand-tight. If the leak stops, the problem is solved. If the leak persists, the connection was compromised somehow, and it has to be replaced with a brand new supply line. If the compression nut doesn’t seal originally, back the nut off having an adjustable wrench and tighten it down once again. Once tightened, back it off and then tighten again. Sometimes the compression fitting has not seated correctly, and by loosening and tightening it two or three times, the fitting will finally seat. Turn the water on after trying to seat the matching. If it still leaks, you will need to install a new source line.
Turn the packing nut to the source valve if it’s water. Sometimes the leak will appear to be coming from the source line, but it’s actually coming from the packing nut on the valve. The packing nut is situated directly in the front of the on/off handle on the valve. Give it a quarter turn with a flexible wrench while the valve is turned on and the supply line is totally attached. You will see a difference instantly. If the water stops leaking, the packing nut was the problem. If the water continues leaking, the packing nut or the valve fixture was compromised. Replacement of this valve is the only fix in this scenario.