Step one: where exactly is the water coming from
Dry the whole fixture, then run it and watch. People routinely replace a cartridge when the actual failure was a two-cent O-ring.
Dripping from the spout with the faucet off. The part that shuts the water off is not sealing — the cartridge, ball assembly, disc, or a compression washer.
Water seeping around the base of the spout when it is running. The O-rings sealing the spout to the body have failed. The valve is fine.
Water appearing at the handle. The packing nut or the bonnet washer under the handle.
Water under the sink but the faucet is dry. Not a faucet fault at all — check the supply line connections and the shutoff valves. This is the version that quietly ruins a cabinet floor.
Step two: identify the type
There are four, and you can usually tell from the outside.
- Cartridge. A single handle that lifts and swivels, or two handles that turn smoothly through about a quarter turn with no gradual tightening. Most common in modern homes. Repair is a whole replacement cartridge.
- Ball. A single handle sitting on a rounded cap, usually over a domed body. Common on older kitchen faucets. Repairs come as a kit — springs, seats and O-rings — because the parts are small and it is not worth doing twice.
- Ceramic disc. A single lever over a wide cylindrical body, feels solid and precise. Very long lived. When they do leak it is usually the inlet seals, not the discs themselves.
- Compression. Two handles that keep tightening the harder you turn, with a definite stop. Older fixtures. The rubber washer at the bottom of the stem is what fails, and it is the cheapest repair of the lot.
Worth knowing
If you cannot tell, take a photo of the faucet and the removed part to the plumbing supply counter. Bringing the actual part beats any amount of description — these vary by manufacturer far more than the four categories suggest.
The repair, in order
The sequence is the same regardless of type, and two steps in it are the ones people skip and regret.
Shut off the supply at the valves under the sink, then open the faucet to confirm it is actually off and to relieve pressure. If the shutoffs will not close — common on valves that have not moved in ten years — stop and shut off at the main instead.
Plug the drain. Every faucet contains at least one small part that will find the opening. This is the step people skip.
Remove the handle. The screw is usually under a decorative cap that prises off. Then the retaining nut or clip, then the working part.
Lay the parts out in order as they come off. Reassembly is where this goes wrong, and photographs of each stage cost nothing.
Replace, grease, reassemble. Use plumber's silicone grease on new O-rings — never petroleum jelly, which degrades rubber. Hand-tight plus a nudge; overtightening cracks plastic and distorts new seals.
Open the supply slowly and run it for a minute, watching. Fast repressurising can dislodge a seal you have just fitted.
Why faucets fail faster here
Hard water is the reason a faucet in Boerne does not last as long as the same faucet elsewhere.
Mineral scale forms on the sealing surfaces inside the valve. A cartridge or disc relies on two smooth faces meeting precisely; scale on either one holds them apart by a fraction, which is all a drip needs. It also makes handles stiff, and stiff handles get forced, which damages the mechanism.
The aerator scales too — that is the weak-flow complaint rather than the drip, and it cleans out in vinegar.
A softener genuinely extends the life of every valve and seal in the house. It is not the reason most people buy one, but it is a real part of the return.
When to stop and call
If the shutoff valves under the sink will not close or start weeping when you turn them, deal with that first — it is a bigger problem than the drip and it is the one that will matter in an emergency.
If the faucet body itself is cracked or corroded, no internal part will fix it.
If a new cartridge drips too, the seat inside the body is likely worn or scaled. Some can be dressed or replaced; some cannot, and that is a faucet replacement.
And if the leak is under the sink rather than at the faucet, treat it as more urgent than it looks. A slow supply-line drip inside a closed cabinet is how people find out about mould rather than about plumbing.