Step 4 of 6
Sink P-trap step 4 of 6: Brush it clean
Push a bottle brush through the U-bend from both ends to scrub off the grease and hair, then rinse it out in another sink or a bucket of water. Look into it: it should be clear all the way round.
Tools: none, just your hands
All 6 steps
What you need
- Bucket or bowl · to catch the water in the trap
- Bottle brush · long and thin
- Rubber gloves · and an old towel
- Slip-joint pliers · only if a nut is stuck
- New slip washers · only if one is cracked or flattened
Questions
Why does a sink have a P-trap?
The water that always stands in its U-bend stops sewer gas coming up the drain into the room. It is also where hair, soap and grease collect, so it is where most sinks clog.
Do I need tools to take a P-trap off?
Usually not: a plastic trap’s slip nuts undo by hand. Slip-joint pliers help if one is stuck; wrap a cloth round a metal nut so they do not scratch it.
Which way does the slip washer go?
Tapered side down, into the U-bend, with the flat side up against the slip nut. The trap maker’s sheet puts it as “cone side down, into the lower side of the trap”.
How tight should the slip nuts be?
Hand-tight, then a little more, about a quarter turn, to seal. Overtightening cracks plastic nuts. Check them again for drips after two or three days.
It still drips after putting it back. What now?
Undo the nut that drips and check its washer: it may be upside down, cracked or squashed. Put it the right way round, or fit a new one, and tighten again.
Safety
Wear gloves: the water in a trap is dirty. Do not pour chemical drain cleaner into a sink you are about to take apart, and if you already have, wear eye protection and let a plumber do it.
About this guide
This guide shows a common bathroom sink’s plastic P-trap, 1¼ inches (32 mm) across: a tailpiece from the basin, a U-bend held on by two slip nuts, each over a tapered washer, and a trap arm into the wall. A kitchen sink’s trap is usually 1½ inches and comes apart the same way.
The steps follow a P-trap maker’s instruction sheet: pull the bend straight down to take it off; the rubber washer goes cone side down into the trap; hand-tighten every nut, then a little more to seal, and test for leaks. The water-flow readings are illustrative.
Sources: P-trap installation instructions (sheet sold with a trap at Lowe’s), iFixit: How to unclog a sink.
The 3D models, drawings and text are our own.