One Drain Is Slow
When only one drain is slow and the rest of the house drains fine, the clog is local to that fixture — usually in the P-trap or the branch line. This can sometimes indicate a buildup of hair and soap in a bathroom drain, grease in a kitchen sink, or a partially blocked trap arm. A plunger or P-trap cleaning often resolves it.
- —Hair and soap buildup in a bathroom sink or tub drain
- —Grease and food debris in a kitchen sink
- —Partial clog in the P-trap or trap arm
- —Slow-running drain that has never been cleaned
Try This First
Safe, simple steps you can try yourself. If any step feels beyond your comfort level, skip it and continue below.
- 1
Try a plunger
Use a flat-cup plunger for sinks. Fill the basin with an inch of water, place the plunger over the drain, and use push/pull strokes to create suction.
- 2
Remove and clean the P-trap
Place a bucket under the trap under the sink. Unscrew the slip nuts and remove the trap. Clean out any debris, then reinstall. This is the most effective fix for a slow sink.
- 3
Use a drain snake or zip tool
For hair in a tub or shower drain, a plastic zip tool (a $3 barbed strip) can pull out a surprising amount of hair. Feed it in, twist, and pull out the clog.
- 4
Avoid chemical drain cleaners
Chemical cleaners are corrosive, can damage older pipes, and rarely clear the full clog. If they don't work and a plumber has to open the line, the chemicals are hazardous to handle.
If the problem is resolved
If the drain flows freely after cleaning the trap or removing hair, you're done. To prevent recurrence, use a drain screen and avoid pouring grease down the kitchen sink.
If the problem persists
If the drain is still slow after cleaning the trap and plunging, the clog is deeper in the branch line. Continue below.
Stop and Call a Plumber If…
- The drain is still slow after cleaning the P-trap and plunging
- The clog returns within a few weeks — there's a deeper issue
- Multiple drains start running slow (main line problem)
- The drain starts gurgling or emitting sewer gas
- ✓Snaking the branch line beyond the P-trap
- ✓Camera-inspecting the branch if the clog is deep or recurring
- ✓Checking for a partially blocked vent pipe
- ✓Determining if the pipe has a belly or sag that collects debris
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Ask the AI PlumberReviewed by Paul Hall, Owner & Licensed Plumber
The Classic Plumber · Knoxville, TN · License #4268. This guidance is general — an onsite inspection may be required for a confirmed diagnosis.