Direct answer: If your faucet drips under the sink, the leak is usually coming from the first pressurized connection above the drip point: most often a loose supply hose connection, a failing faucet supply hose, a leaking pull-down sprayer hose, or water tracking down from the faucet body or shank.
Most likely: Start by drying everything completely, then run only the faucet while watching with a flashlight. The first spot that turns wet matters more than where the drip finally lands.
Under-sink faucet leaks fool people all the time because water runs along hoses, mounting hardware, and the sink bottom before it drops. Reality check: the puddle is rarely directly under the actual leak. Common wrong move: tightening every nut hard enough to crack a fitting or twist a hose.
Don’t start with: Don’t start by replacing the whole faucet or buying random hoses just because the cabinet floor is wet.
The cabinet stays dry until you open the faucet, then you see drips or a fast bead forming under the sink.
Start here: Watch the faucet supply hoses, sprayer hose, and faucet shank while someone runs hot and cold separately.
You find a steady drip or dampness under the sink even when nobody has used the faucet for hours.
Start here: Check the pressurized hot and cold faucet supply hose connections at the shutoff valves and where they attach to the faucet.
Water forms around the mounting hardware or runs down the threaded faucet shank.
Start here: Dry the faucet underside and check whether water is coming down from above the sink deck or from the faucet body itself.
You see water on the spray hose, weight, or loop of hose under the sink, usually while using the sprayer.
Start here: Run the faucet, then use the sprayer head and watch the full hose length for a split or leaking connection.
This is the most common under-sink faucet leak, especially if the drip happens with the faucet off as well as on.
Quick check: Dry the hot and cold hose ends at both connections, wrap each with a dry paper towel, and see which one wets first.
If the leak shows up mainly when using the sprayer or moving the spout, the hose often has a split or a bad end fitting.
Quick check: Run water through the sprayer and watch the hose where it bends, rubs, or passes the counterweight.
A leak above the sink can run down the faucet shank and make it look like an under-sink connection problem.
Quick check: Wipe the faucet dry above and below the sink, then look for fresh water starting at the faucet base before anything below gets wet.
If water appears inside the faucet body and then comes down through the center under the sink while the faucet runs, the internal sealing parts may be leaking.
Quick check: With the underside dry, run the faucet and look for water emerging from the faucet body or shank area rather than from a hose fitting.
You need to separate a true faucet leak from water that has simply traveled along parts under the sink.
Next move: If you spot one exact fitting or hose turning wet first, you already have the main repair path. If everything stays dry with the faucet off, the leak likely happens only during use and you need to test it under flow.
What to conclude: A leak with the faucet off points to a pressurized connection or hose. A leak only during use points more toward the sprayer hose, faucet body, or water tracking down from above.
Loose or failing faucet supply hose connections are the most common cause and the least destructive place to start.
Next move: If a careful snug stops the drip and the connection stays dry, monitor it through several uses before calling it fixed. If the same connection still weeps or the hose body is wet, the faucet supply hose is the likely failed part.
What to conclude: A connection that immediately rewets is usually dealing with a bad hose end seal, damaged fitting, or a worn faucet supply hose rather than simple looseness.
Some faucet leaks only show up when water is moving, and the pull-down hose is a common lookalike.
Next move: If the leak clearly follows the sprayer hose during spray use, you have a solid hose-replacement diagnosis. If the hoses stay dry but water starts at the faucet center or shank, move to the faucet body and base check.
A faucet base leak often runs down the shank and fools people into replacing good hoses.
Next move: If you confirm water is tracking down from above, stop chasing the under-sink fittings and address the faucet base or upper-body leak. If the top stays dry and water still appears from the center underside while the faucet runs, the internal faucet parts are more suspect.
By now you should know whether the leak is at a connection, in a hose, or inside the faucet body.
A good result: If all tested conditions stay dry, the repair path was correct.
If not: If a new hose or cartridge does not stop the leak, the faucet body or another nearby plumbing connection may be the real source and it is time for a closer in-person diagnosis.
What to conclude: You only want to buy the part that matches the leak pattern you actually saw. Guessing here usually turns one trip into three.
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That usually points to a leak that happens under flow, not a constant pressure leak. The most common spots are the pull-down faucet sprayer hose, a faucet supply hose that opens up under pressure, or water leaking through the faucet body and running down the center shank.
Yes. Water from the faucet base or handle area can run down the faucet shank and drip below the sink, making the under-sink fittings look guilty when they are not. Dry both above and below the sink and watch for the first wet point.
Only a little, and only if the fitting is clearly just loose. If a careful snug does not stop it right away, or the hose itself is wet, stop tightening and treat it as a bad hose or damaged fitting. Cranking harder often makes the repair worse.
The leak usually shows up when you use the sprayer or move the hose. Look for a split, rub mark, pinhole spray, or a drip at one of the hose ends near the weight or where the hose bends.
A cartridge becomes more likely when the external faucet hoses stay dry but water leaks through the faucet body or center shank while the faucet is running. It is less likely if the drip is clearly starting at a hose connection under the sink.
Not usually. Many under-sink faucet leaks come from a faucet supply hose or pull-down faucet sprayer hose. Replace the whole faucet only when the body is cracked, parts are unavailable, or the leak source is in the faucet body and repair is not practical.