To fix a leaky faucet, do not start by taking it apart — start by naming it. The most common cause of a drip is a single worn sealing part, but which part depends entirely on the faucet type: a rubber washer on a compression faucet, the cartridge itself on a cartridge faucet, the seats and springs on a ball faucet, or the inlet seals on a ceramic-disc faucet. Identify the type, note where the water appears — from the spout, around the handle, or at the base — shut the water off, and replace that matching part.
Shut the water off first, every time. Moen states that any repair on its faucets requires the water supply to be shut off, and that failing to do so could result in flooding or injury. Close both shut-off valves under the sink, open the faucet to confirm the water is off, and plug the drain so the first screw you drop does not disappear. If a shut-off valve will not turn or drips when closed, stop — that valve is now the job, and a plumber’s job if you cannot isolate the water at the main.
Step 1: Name the leak before you name the part
Dry the whole fixture with a towel, then watch it: run the faucet, shut it off, observe for a minute. The location narrows the part list more honestly than any guess:
- Drip from the spout with the faucet off. The part that shuts the water off is no longer sealing: the cartridge on a cartridge faucet (Moen gives exactly that diagnosis for its faucets), the seats and springs on a ball faucet, the washer on a compression faucet, the seals or disc cartridge on a ceramic-disc faucet. Delta Faucet’s own guidance for a two-handle kitchen faucet dripping from the spout starts the same way: the seats and springs wear out, and replacing them is the first fix.
- Leak around or under the handle, usually while the faucet is running. Think O-rings, packing or a loose retaining nut. On a single-handle faucet a handle leak can run down and puddle at the base, imitating a base leak — as Moen warns — so confirm the highest wet point, not the lowest puddle.
- Leak at the base of the spout where it meets the deck. On a swivelling kitchen spout this is typically the spout O-rings. On other faucets, water at the base is often the handle leak above travelling down, or a supply connection below the sink — check under the cabinet by hand, with a torch, before dismantling the faucet.
- Leak under the sink. Supply lines, shut-off valves and drain connections live there; none is fixed by a cartridge. Dry everything, run the faucet, and find the wet fitting. A leak at a supply connection or valve is a different repair, closer to the shut-off work in toilet keeps running, and a corroded pipe or a valve that will not close belongs to a plumber.
Step 2: Identify your faucet type
Four mechanisms cover nearly every household faucet. You can tell them apart by the handles and how they move:
| Type | How to recognise it | Part that usually causes a spout drip |
|---|---|---|
| Compression | Two handles that keep turning and tighten down with a squeeze at the end; older fixtures | Rubber washer at the bottom of the stem, and the valve seat beneath it |
| Cartridge | One handle that lifts and swivels, or two handles that turn smoothly about a quarter turn; most common in modern homes | The cartridge — a single replaceable unit, brand- and model-specific |
| Ball | Single handle sitting over a rounded, domed cap; common on older kitchen faucets | Two small rubber seats on springs under the ball, plus O-rings |
| Ceramic disc | Single lever over a wide, solid cylindrical body; smooth, precise movement, about a quarter turn | Inlet seals under the disc cartridge; the discs themselves rarely fail |
The handle test settles most arguments. Multiple full turns with a tightening feel at the end means compression. A short, smooth quarter-turn with no squeeze means cartridge or ceramic disc. A single handle that moves in every direction over a dome means ball. When in doubt, photograph the faucet and note any brand name on it before you shop — cartridges are not interchangeable between makers, and often not between one maker’s own ranges.
Tools and parts to have ready
Basic tools for any of the four repairs: an adjustable wrench, Phillips and flat screwdrivers, an Allen (hex) key set, needle-nose pliers, a cloth or tape to protect finished surfaces, silicone plumber’s grease, and the replacement part itself — washer and O-ring assortment for compression, the matched cartridge for cartridge and ceramic-disc types, or a seats-and-springs kit for a ball faucet. Take the old part with you when you buy: washers must match in diameter and thickness, seats and springs come in maker-specific sizes such as Delta’s RP4993 sets, and a cartridge must match in length, stem shape and orientation tabs. Lay parts out in removal order on a towel and photograph each stage; reassembly errors cause more repeat leaks than worn parts do.
The repair sequence that applies to every type
- Shut off both supplies under the sink (clockwise), open the faucet to drain pressure and confirm nothing flows, and plug the drain.
- Remove the handle. The screw hides under a decorative cap that prises off, or is a set screw in the side or underside of a lever, loosened with an Allen key.
- Remove the retaining hardware — a bonnet nut, a packing nut or a U-shaped retaining clip — noting its order and orientation.
- Lift out the working part (stem, cartridge, ball assembly or disc cartridge) straight, without prying against the faucet body.
- Replace the worn sealing part for your type, following the type sections below, and lightly grease new O-rings with silicone grease. Never use petroleum jelly or petroleum-based lubricants on rubber seals; Moen’s cartridge service instructions specify the supplied grease for the seals and warn against petroleum products, which degrade rubber.
- Reassemble in reverse, snug rather than forced — overtightening distorts new seals and cracks plastic parts.
- Turn the water back on slowly, with the faucet open to flush air and debris, then shut it and watch the spout, handle and base, and check under the sink.
Compression faucets: replace the washer, check the seat
Unscrew the packing nut and draw the whole stem out. At the bottom of the stem is the rubber washer, held by a small brass screw. Remove the screw, fit an exact-size washer, and refit the screw firmly without crushing the rubber. While the stem is out, run a fingertip over the valve seat down in the faucet body — the brass surface the washer presses against. If it feels rough or pitted, a new washer will fail again quickly: a removable seat can be unscrewed with a seat wrench and replaced, and a fixed seat can be resurfaced with a seat-dressing tool, but a badly corroded body makes a whole-faucet replacement more sensible than a third washer.
A compression faucet that leaks around the stem while running has a packing or stem O-ring fault, not a seat-washer fault. Replace that O-ring or packing while the stem is out — doing both in one visit is cheaper than opening the faucet twice.
Cartridge faucets: replace the cartridge as a unit
With the handle off, remove the retaining clip or nut. Moen’s service-kit procedure for its 1225 cartridge shows the pattern makers expect: the cartridge’s small and large O-rings and grommets sit in specific grooves, and a seal placed in the wrong groove will leak — which is why most makers intend the whole cartridge to be swapped rather than rebuilt. Grip the stem and pull the cartridge straight out; a cartridge seated for years may need a gentle quarter-turn to break it free, and a puller tool exists for stubborn ones. Do not lever it out with a screwdriver against the valve body.
Before the new cartridge goes in, flush and wipe the valve body clean — grit left inside scores the new seals. Note the old cartridge’s orientation (any notch, tab or hot/cold marking) and insert the new one the same way, refit the clip or nut without forcing it, and reassemble. If hot and cold arrive reversed, makers such as Moen direct you to rotate the stem 180 degrees rather than removing the cartridge again. The same shut-off-first discipline applies to the neighbouring jobs in this family — no hot water in the house starts with the same “confirm the supply before condemning the part” logic at the water heater.
Ball faucets: replace the seats and springs as a kit
Loosen the handle set screw, lift the handle, unscrew the cap and lift out the cam and the ball. Under the ball sit two rubber seats, each on a spring. Hook them out with a pencil or an Allen key, as Delta directs, wipe the ports clean, and fit the new set: the large end of each spring goes into the faucet body and the small end into its seat. Inspect the ball while it is out: a pitted or scratched ball will not seal against new seats, and if the drip persists after new seats and springs, Delta’s sequence is to replace the stem or ball-side components next, not repeat the same kit. Refit the ball with its peg or slot aligned to the body, then the cam and cap, snug rather than cranked down.
Ceramic-disc faucets: seals first, disc cartridge second
Remove the handle and the escutcheon or retaining hardware to lift the disc cartridge out. Kohler’s service-kit instructions capture the essentials: water off, pressure relieved, cartridge out, body wiped clean, and the replacement’s tabs aligned with the slots so it seats in its one correct orientation. The ceramic discs themselves are hard-wearing; the leak is usually the rubber inlet seals beneath the cartridge, distorted by grit or age. Clean the seal seats, fit new seals, and only replace the disc cartridge if a disc is visibly cracked or the leak survives new seals. Flush the body first — grit between the discs defeats the repair.
When to call a plumber
Call rather than continue if: a shut-off valve will not close, leaks when closed, or is heavily corroded; the leak is under the sink at a supply line, valve or pipe rather than in the faucet; the faucet body itself is cracked or the seat is corroded beyond dressing; a cartridge will not come out with reasonable force and the puller; or the drip survives a correctly matched new part fitted in the right orientation — which suggests body wear or a supply-pressure problem rather than another seal. If several faucets in the house drip at once, suspect the water pressure itself, not several worn parts failing together. Renters should also stop at the shut-off stage in many leases: the faucet is the landlord’s fixture, and a written record of the drip protects you better than a repair that goes wrong. If the leak has been dripping into a cabinet or wall, deal with the water damage promptly — a stopped drip does not dry a soaked cabinet by itself, much as a drained appliance still needs follow-through, as in dishwasher not draining.
Frequently asked questions
Why does my faucet drip only at night? Often it does not — a slow drip is audible in a quiet house, and higher overnight water pressure as neighbourhood demand falls can push past a worn seal that holds during the day. The part is still worn; fix it the same way.
Can I just replace the O-rings instead of the cartridge? Sometimes — for a handle or base leak on a cartridge faucet, where O-rings are the seal at fault. For a spout drip, makers direct you to the cartridge itself: the seals that shut the water off are inside it and are not reliably serviceable separately.
How do I know whether the hot or the cold side is leaking on a two-handle faucet? Shut off only the hot supply under the sink and wait. If the drip stops, the hot side is the culprit; if it continues, restore the hot and shut off the cold to confirm. Delta’s procedure troubleshoots the hot valve first this way.
Is a dripping faucet urgent? It will not flood the house, but it worsens as the seat erodes. Fix it within days, and shut the supplies off if you have to wait for a matched part.
How much water does a dripping faucet actually waste? More than it looks. The U.S. Environmental Protection Agency’s WaterSense program puts it plainly: a faucet dripping once per second wastes more than 3,000 gallons a year — roughly the water for more than 180 showers — and worn washers and gaskets are the usual cause it names.
Should I repair the faucet or replace the whole thing? Repair it when the fault is one worn part — a washer, a cartridge, a set of seats and springs — and the body is sound. Replace it when the body itself is cracked or corroded, the seat is worn beyond dressing, the maker no longer supplies the cartridge, or a correctly matched new part still drips. What does not make sense is a third washer into a corroded body: the part is cheap, the leak is not in the part.
This article is general information based on the faucet manufacturers’ guidance linked above and checked in November 2026. Designs and cartridge fittings vary by maker and model — match every replacement part to the part you removed, follow your model’s instructions where they differ, and stop at any corroded valve, pipe or fitting and use a licensed plumber.