You’re staring at that crusty, lime-scaled sprout and wondering if today is the day it finally snaps off. Honestly, most people wait until the drip-drip-drip sounds like a drum kit in their skull before they even think about how to change a faucet in the bathroom. It’s intimidating. There’s water, there’s cramped spaces under the sink, and there’s the very real fear of flooding your hallway. But here’s the thing: it’s mostly just unscrewing stuff and screwing it back on.
I’ve seen folks spend $300 on a plumber for a job that takes forty-five minutes if you don't get distracted by your phone. You don't need a van full of tools. You mostly just need a wrench that actually fits and a bit of patience for when the old nut won't budge.
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Why your old faucet is fighting you
Before you even touch the new hardware, you have to kill the old stuff. This is where the nightmare starts. Rust. Corrosion. That weird green gunk called verdigris that builds up on copper and brass over a decade. If you live somewhere with hard water, like Phoenix or Indianapolis, those mineral deposits act like natural superglue.
You’ll crawl under there and realize the mounting nuts are basically fused to the shank. This is why you need a basin wrench. It’s a weird, spindly tool with a floppy head that reaches up into that dark "no man's land" behind the sink bowl. Without it, you’ll be scraping your knuckles and swearing at a standard crescent wrench that can't quite turn.
Turning off the juice
First step? Shut-off valves. They’re those oval handles under the sink. Turn them clockwise. If they don't move, stop. Do not force them with a giant pair of pliers or you might snap the stem and then you actually will have a flood. If they’re frozen, you might have to shut off the main water line to the whole house. Once the water is "off," open the faucet handles to bleed out the pressure and the leftover water. If you skip this, you’re getting a face full of lukewarm pipe water the second you loosen the supply lines.
The messy middle of how to change a faucet in the bathroom
Disconnect the supply lines first. These are the flexible braided hoses (usually) connecting the shut-off valve to the faucet. Use two wrenches: one to hold the valve steady and one to turn the nut. If you don't hold the valve steady, you risk twisting the copper pipe coming out of the wall. That’s a "bad day" scenario.
Now, the pop-up drain. People forget this part. Most new faucets come with a matching drain assembly. You have to disconnect the pivot rod—the horizontal stick that moves the stopper up and down—and then unscrew the large nut holding the drain flange to the sink.
Dealing with the "Triple Threat" hole configuration
Sinks usually come in three flavors: single-hole, 4-inch centerset, or 8-inch widespread. You need to know what you have before you buy the replacement.
- Centerset: The most common. Three holes, four inches apart. The faucet and handles are one solid unit.
- Widespread: Three separate pieces. This gives you more room to clean between the handles, but it's a bit more of a pain to install because of the extra hoses underneath.
- Single-hole: Just one hole. If you’re putting a single-hole faucet into a three-hole sink, you’ll need an "escutcheon" plate to hide the extra holes.
Putting the new one in (The easy part)
Clean the sink surface. Seriously. Get all that old plumber’s putty and gunk off the porcelain. If the surface isn't smooth, the new gasket won't seal, and water will leak through the holes every time you splash around.
Most modern faucets from brands like Delta, Moen, or Kohler use a plastic gasket or a pre-installed foam seal. If yours doesn't, you’ll need a rope of plumber’s putty. Roll it in your hands like Play-Doh until it’s a thin snake, wrap it around the base, and set the faucet down.
The tightening dance
Drop the faucet through the holes. Underneath, you’ll slide on the washers and the mounting nuts. Here’s a tip: have someone hold the faucet straight from above while you tighten from below. There is nothing more annoying than finishing the job, crawling out from under the cabinet, and seeing your new faucet is crooked by five degrees.
Let's talk about the drain assembly
This is where the leaks usually happen. You’ll take the new drain flange, slather the underside with plumber's putty (unless the instructions specifically say use the provided rubber gasket), and shove it through the hole from the top. Underneath, you have a big rubber gasket, a plastic washer, and a large locking nut.
Don't over-tighten. If you crank it too hard on a thin porcelain or plastic sink, you can actually crack the basin. Snug is good. Tight is fine. "Herculean" is a mistake.
Then comes the P-trap. That U-shaped pipe. If it's old and plastic, it might just crumble when you touch it. If it’s metal and rusted, just replace it. A new plastic P-trap kit costs ten bucks and will save you a leak in three months. Connect the tailpiece of the new drain to the P-trap using the slip nuts and washers. Make sure the beveled (pointed) end of the washer is facing the joint.
The moment of truth: Testing for leaks
Take the aerator—the little screen at the tip of the spout—off. You want to flush the lines. Sometimes bits of sediment or old rubber from the valves break loose, and if the aerator is on, they’ll clog it instantly.
Slowly turn the water valves back on. Check the connections at the wall. Check the connections at the faucet. Now, turn the faucet on full blast—both hot and cold. Let it run for a minute.
Where to look for "stealth" leaks
- The base of the faucet: If water is pooling on the counter, your base gasket or putty isn't doing its job.
- The supply line nuts: If there's a slow drip, give it a quarter-turn with the wrench.
- The pop-up drain nut: This is the most common culprit. If it drips here, you might need to adjust the rubber gasket underneath.
Maintenance and the "Why" behind the upgrade
Changing a faucet isn't just about aesthetics. Older faucets, especially those made before the mid-90s, often don't meet modern "Low Lead" standards. According to the EPA’s Safe Drinking Water Act, newer fixtures are required to have significantly lower lead content. Plus, modern faucets use aerators that limit flow to about 1.2 to 1.5 gallons per minute (GPM), compared to the old 2.5 GPM water-wasters. You're saving money on the water bill while making the bathroom look less like a 1974 time capsule.
If you run into a situation where the copper pipes are literally crumbling or the shut-off valves won't stop leaking even after you've tightened the packing nut, that’s your signal to stop. There is no shame in calling a pro if the house’s plumbing infrastructure is failing. But if the pipes are solid, you’ve got this.
Actionable Next Steps
- Measure your "centers": Use a ruler to check the distance between the center of the far-left hole and the center of the far-right hole. If it’s 4 inches, buy a centerset. If it’s 8, go widespread.
- Buy a Basin Wrench: Do not try to do this with just a pair of pliers. It’s $15 at any hardware store and will save you three hours of frustration.
- Get new supply lines: Don’t reuse the old ones. The rubber seals inside them get brittle over time. Spending $12 on new braided stainless steel lines is cheap insurance against a burst pipe.
- Clear the deck: Empty everything out from under the sink before you start. You need room to lie on your back. Put a towel down to catch the inevitable half-cup of water that’s sitting in the lines.
- Take a photo: Before you take anything apart, snap a picture of the setup underneath. If you forget how the pivot rod for the drain connects, you’ll be glad you have the reference.
Once the air stops sputtering out of the tap and the water runs clear, screw that aerator back on. You’re done. You saved a few hundred dollars and you don't have to listen to that rhythmic dripping while you're trying to sleep anymore.