That steady tick, tick, tick at two in the morning is more than annoying. It is money running down the drain. Understanding what causes a faucet to drip comes down to a handful of worn parts inside the valve, and in most cases you can fix it yourself for less than $30 in an afternoon. A single drip per second wastes roughly 3,000 gallons a year, enough to fill about 60 average bathtubs, so a leak you have been ignoring for six months has already cost you real dollars on the water bill.
After 20 years of service calls, I can tell you the vast majority of drips trace back to four or five failure points. Which one you have depends mostly on the type of faucet sitting on your sink. Let me walk you through the causes, how to tell them apart, and what each repair actually costs.
- First, Identify Your Faucet Type
- Worn Rubber Washers: The Number One Cause
- A Corroded or Pitted Valve Seat
- Worn O-Rings and Handle Drips
- A Damaged Cartridge
- Ceramic Disc Wear and Ball Assembly Problems
- High Water Pressure and Water Hammer
- How to Diagnose Which Part Is Failing
- Repair Costs and When to Call a Pro
First, Identify Your Faucet Type
You cannot fix a drip until you know what is inside the body. There are four common valve designs, and each fails in its own way.
- Compression faucets: The old-school design with two separate handles, one for hot and one for cold. You feel resistance as you tighten the handle down. These use rubber washers and are the drippiest style ever made.
- Ball faucets: A single handle that swivels over a rounded cap, common on older kitchen sinks. Inside sits a slotted metal or plastic ball riding on spring-loaded rubber seats.
- Cartridge faucets: Single or double handle, but the handle moves smoothly with no compression feel. A replaceable cartridge sleeve controls flow. Moen, Delta and Price Pfister all use versions of this.
- Ceramic disc faucets: A premium single-handle design with two polished ceramic discs that slide over each other. Durable, but not immune to failure.
Pull the handle and look. If you see a large brass nut and a stem with a screw holding a black rubber washer at the bottom, you have a compression faucet. If a plastic sleeve lifts straight out, it is a cartridge. Knowing this narrows the cause immediately.
Worn Rubber Washers: The Number One Cause
On compression faucets, the washer is a small rubber or nylon disc at the bottom of the stem. Every time you shut the water off, that washer presses hard against the valve seat to stop flow. Metal on rubber, thousands of times a year, grinds the washer flat and cracked.
Once the washer no longer seals cleanly, water sneaks past and drips from the spout. This is the classic cause of a dripping spout on a two-handle sink. A pack of assorted washers costs about $3 to $6 at any hardware store, and swapping one takes ten minutes: shut off the supply, unscrew the packing nut, pull the stem, remove the brass screw, and press in a matching washer. Size matters here. A washer that is even 1/16 inch too small will keep dripping.
A Corroded or Pitted Valve Seat
Sometimes you replace the washer and the drip comes right back within a week. When that happens, the valve seat is the villain. The seat is the brass ring the washer presses into, and years of mineral-laden water pit and roughen its surface. A rough seat chews through new washers and never lets them seal.
You have two options. A seat-dressing tool, about $10 to $15, grinds the brass smooth again in a couple of minutes. Or you replace the seat outright if it is the removable type, using a seat wrench that costs around $8. If the seat is not removable and the pitting is deep, the whole faucet body may need replacing. This is one of the more overlooked answers to what causes a faucet to drip after an otherwise correct repair.
Worn O-Rings and Handle Drips
Not every leak comes out of the spout. If water seeps from around the base of the handle, the O-ring is the usual suspect. The O-ring is a small rubber loop that seals the stem or cartridge where it enters the faucet body. Over five to ten years the rubber hardens, shrinks and cracks.
O-rings are dirt cheap, often 50 cents to $2 each, but you must match the exact diameter and thickness. I keep a plumber’s O-ring assortment box in the truck for this reason. A quick smear of plumber’s silicone grease on the new ring extends its life and keeps the handle turning smoothly. Ignore a leaking O-ring and the constant moisture will corrode the metal underneath and warp the cabinet base below.
A Damaged Cartridge
Cartridge faucets do not use washers, so when they drip the fix is almost always a new cartridge. Inside the sleeve are rubber seals and precise ports that meter hot and cold water. Sediment scores those seals, and hard-water scale builds up until the cartridge can no longer close fully.
Replacement cartridges run $10 to $30 depending on brand. Moen’s 1225 and Delta’s RP series are the most common. The trick is buying the exact model, because a Moen cartridge will not fit a Delta body. Bring the old one to the store or note the faucet’s model number stamped under the spout. Pulling a stubborn, scaled-in cartridge sometimes takes a puller tool, roughly $15, but the swap itself is straightforward: shut off water, remove the retaining clip, lift the old cartridge, drop in the new one.
Ceramic Disc Wear and Ball Assembly Problems
Ceramic disc faucets are the most durable, but nothing lasts forever. The two discs are polished flat to seal against each other. Grit from a water heater flush or a repair upstream can scratch them, and a scratched disc drips. The disc cartridge is a single replaceable unit, usually $20 to $40.
Ball faucets are the fussiest to diagnose because several small parts share the load. Under the ball sit two rubber seats, each backed by a little spring. Those springs weaken and the seats compress until they no longer push firmly against the ball. A ball-faucet repair kit, about $15, includes new springs, seats, cam and O-rings. Replace all of them at once. Doing just one part while the rest are worn is a false economy that has you back under the sink in a month.
High Water Pressure and Water Hammer
Sometimes the faucet parts are fine and the plumbing itself is the problem. Residential water pressure should sit between 40 and 60 psi. Anything over 80 psi stresses every washer, seal and cartridge in the house, and you will notice faucets that drip only at certain times of day, usually late at night when neighborhood demand drops and street pressure spikes.
Buy a $12 pressure gauge that threads onto a hose bib and check it. If you read over 80 psi, install a pressure-reducing valve, or PRV, on the main line. A PRV costs $50 to $100 for the part, and a plumber will charge $250 to $400 installed. It pays for itself by protecting the water heater, dishwasher and every faucet in the house.
Water hammer, that banging you hear when a valve shuts, sends shock waves that hammer seals loose over time. Adding hammer arrestors or making sure air chambers are charged can stop the drip that follows. Loose or cross-threaded parts from a sloppy prior repair cause the same trouble, so if a faucet started dripping right after someone worked on it, recheck that the packing nut and mounting hardware are snug and seated straight.
How to Diagnose Which Part Is Failing
Work through it methodically and you will pin down the cause without guessing.
- Note where the water appears. Spout drip points to washers, seats, cartridges or discs. Handle-base leak points to O-rings or packing.
- Note which handle. On a two-handle sink, feel which side is warm. If only the hot side drips, you only need to service the hot stem.
- Check the pressure with a gauge before tearing anything apart, especially if multiple fixtures drip.
- Open the valve and inspect. A flattened washer, a gritty seat, a cracked O-ring or a scaled cartridge usually reveals itself the moment you have it in the light.
Always shut off the angle stops under the sink first, then open the faucet to bleed pressure before you disassemble anything.
Repair Costs and When to Call a Pro
The parts to answer what causes a faucet to drip are cheap. Washers, O-rings and seats run $3 to $15, and a full cartridge or ball kit tops out around $30. Basic hand tools cover the labor if you do it yourself.
If you would rather not, a plumber’s service call runs $75 to $150 for the first hour, which is usually all a drip repair takes. Weigh that against the water waste. At 3,000 gallons a year per dripping second, plus the sleep you lose, a $100 repair or a $20 do-it-yourself Saturday is money well spent. If a faucet is over 15 years old, corroded green at the base, or you have already replaced parts twice, stop patching it and put in a new faucet for $80 to $250. Some drips are the faucet telling you its time is up.
