Pull the stopper out of the drain. In most bathroom sinks it lifts free once you unscrew the pivot rod nut under the basin; in a shower, the cover pries up or comes out with a quarter turn. Do this before you spend a dollar, because a large share of bathroom clogs sit in the first four inches of pipe, wrapped around the stopper itself, and nothing on a store shelf clears that spot faster than your gloved hand and a paper towel. Below is the full escalation, ordered by cost and mess, with a clear line marking where the job stops being yours.
Quick answer: Work from cheapest to most invasive. Clear the stopper and visible hair, flush with hot water and dish soap, plunge with a cup plunger, open the P-trap, then run a 25-foot hand snake. Call a plumber the moment more than one fixture backs up at once, or when the snake hits something past the trap that will not clear. Skip chemical drain cleaners at every stage.
Step 1: clear the stopper and the first few inches
With the stopper out, look into the drain with a flashlight. In bathroom sinks, tubs, and showers, the usual culprit is a mat of hair bound together with soap scum, and it is almost always within reach.
Buy a barbed plastic drain strip if you do not own one. It is a flexible plastic band, about 20 inches long, with backward-facing teeth, and it costs around three dollars at any hardware store. Feed it down, twist once, and pull straight up. Repeat until it comes back clean. A wire coat hanger with a small hook bent into one end does the same job.
Two rules here. Always pull debris up and out, never push it deeper, because a clog you compact becomes a clog you cannot hook. And wear gloves; a six-month hair mat smells worse than you expect.
When the drain looks clear, run hot water for a full 30 seconds. If it swirls straight down without pooling, reassemble the stopper and stop reading. If it still drains slowly, the blockage sits deeper, so continue.
Step 2: flush with hot water and dish soap
This step targets kitchen sinks, where the enemy is congealed grease rather than hair. Squirt about two tablespoons of dish soap directly into the drain, then slowly pour in two quarts of very hot water. Dish soap is engineered to break grease into particles that water can carry, which is exactly the failure mode of a kitchen drain.
Mind the temperature. Water straight off a rolling boil can crack a cold porcelain basin and can soften PVC pipe, which is typically rated to about 140 degrees Fahrenheit. Let a boiled kettle sit for two minutes, or use the hottest water your tap produces. Pour, wait five minutes, then run the tap and watch the flow.
The famous baking soda and vinegar treatment deserves an honest word. The fizz is carbon dioxide, and it does no scrubbing on its own. That said, half a cup of baking soda followed by a cup of vinegar, left for 15 minutes and chased with hot water, can loosen a light film of buildup, and everything involved costs pennies. Treat it as a maybe, useful on a sluggish drain, useless on a blocked one.
Repeat the hot flush twice before moving on; grease releases in stages, and the second pour often finishes the job.
Step 3: plunge with a seal, not with muscle
Plunging fails for one reason more than any other: the wrong plunger. You want a cup plunger, the simple flat-rimmed dome, for sinks, tubs, and showers. The flanged plunger with the fold-out sleeve is shaped for toilets, and its rim will not seal on a flat surface.
The second failure is air leakage. A plunger works by moving a column of water against the clog, and every opening in the system bleeds off that pressure. Stuff a wet rag firmly into the sink’s overflow opening, the small hole near the rim. On a double kitchen sink, plug the second drain with a stopper and hold it down. On a tub, pack the rag into the overflow plate below the faucet.
Run enough water to cover the plunger’s cup by an inch, since water transmits force and air merely compresses. A thin smear of petroleum jelly on the rim improves the seal on textured surfaces. Then work in sets: 15 to 20 sharp strokes, keeping the seal the whole time, followed by a quick pull off the drain on the last stroke. Two or three sets is a fair trial. If the water suddenly gulps down, run hot water for a minute to carry the loosened material past the trap.
Field note: Chemical drain openers earn their bad reputation. The caustic ones generate heat that stresses old metal pipes, and when they fail, they leave a pipe full of lye-laced water that someone, you or the plumber you eventually call, has to open a trap into. A hook, a plunger, and a snake fix most of what the bottle promises, without the hazard.
Step 4: open the P-trap
The P-trap is the U-shaped bend directly under the sink, and it exists to hold water as a seal against sewer gas. It is also where dropped objects, coffee grounds, and grease plugs collect. Opening it sounds like plumbing; it is closer to unscrewing a jar.
Put a bucket under the trap; it holds roughly a pint of gray water and will release all of it. Loosen the two slip nuts, one at each end of the bend. On white PVC they usually turn by hand; on metal traps, use channel-lock pliers with tape on the jaws to protect the finish. Pull the bend free, dump it into the bucket, and scrub the inside with a bottle brush or a rag on a stick.
While the trap is off, shine a flashlight into the pipe stub in the wall. If you can see the blockage, hook it out now. Reassemble with each washer seated flat in its nut, tighten hand-tight plus a quarter turn, and run water while watching for drips. The whole operation takes ten minutes, and it is one of the highest-value moves in the entire set of repairs worth learning to do yourself.
Step 5: run a drain snake
If the trap was clear and the drain still will not flow, the clog lives in the branch line inside the wall. This is hand-auger territory. A quarter-inch by 25-foot drum snake costs about 25 to 35 dollars and belongs in any serious home tool kit.
The easiest access is the one you already opened: with the P-trap off, feed the cable directly into the wall stub. You skip the tight bends under the basin and reach the blockage with most of your 25 feet to spare. Push the cable in until you feel resistance, lock the setscrew, and crank the drum clockwise while applying light forward pressure.
Learn to read what the cable tells you. A soft, spongy stop that gives as you crank is the clog, so keep turning until the cable surges forward, then pull back slowly and drag the debris out with it. A hard, abrupt stop is usually a fitting where the pipe turns, so pull back a few inches, rotate, and guide the tip past it rather than forcing it. For a tub, feed the snake through the overflow plate opening rather than the drain, since the path is straighter.
Run several minutes of hot water afterward. A snake pokes a hole through a clog more often than it removes one, and the flush is what scours out the remainder.
When to stop and call the plumber
Everything above assumes the problem is local to one fixture. Certain signs say otherwise.
Call a plumber when more than one fixture backs up at the same time, when flushing the toilet pushes water up into the tub or shower, or when a floor drain in the basement overflows. Those point to the main line, past the reach of a 25-foot cable. Call when your snake hits a firm blockage near its full length, when a clog you cleared returns within a couple of weeks, which suggests a partial obstruction or a root intrusion, or when the drain gurgles and smells of sewage even while flowing. And if your home has old galvanized steel drains that shed rust flakes when you snake them, stop early, because aggressive cable work can open a leak.
A plumber brings a motorized auger with 75 feet or more of cable, plus a camera to see what it is fighting. When you call, list what you already tried. Saying the trap was clean and a hand snake stalled at 20 feet turns a diagnostic visit into a targeted one, and that usually shows up on the bill in your favor.