Replacement P-Trap (UK Guide: Sizes, Types & Installation)
A P-trap is the essential curved pipe section under your sink that holds water to prevent sewer gases from entering your home. If you've spotted a leak or a smell, it's time for a replacement.
What does a P-trap actually do?
In UK plumbing, the P-trap is a simple but vital component designed to:
- Create a Water Seal: Blocks foul drainage odours from entering the room.
- Connect Waste: Securely joins the sink waste to the main drainage pipe.
- Catch Debris: Allows for easy removal to clear hair or grease blockages.
Common Signs You Need a Replacement
P-traps are common sources of under-sink leaks. Look out for these red flags:
Where to Buy Replacement P-Traps in the UK
Pricing typically ranges from £3 to £15 depending on the type and brand. We recommend buying from established UK trade merchants to ensure the fittings meet British Standards for waste drainage.
| Retailer | Stock Status | Benefit | Link |
|---|---|---|---|
| Screwfix | In Stock | Huge range of McAlpine & Floplast | View Range |
| Toolstation | Available | Great value on standard 40mm traps | Check Stock |
| City Plumbing | In Stock | High-quality trade grade parts | View Prices |
How to Install a New P-Trap
Replacing a trap is a straightforward DIY task that usually requires no tools other than your hands.
Clear the Area
Place a bucket or towel directly under the old trap. There will be standing water inside the "U" bend that will spill out once unscrewed.
Unscrew the Old Unit
Unscrew the large plastic nuts at both ends of the trap by hand. If they are stuck, use an adjustable wrench gently. Slide the old unit out and clean the pipe ends.
Fit New Washers & Tighten
Slide the new nuts and washers onto the pipes. Align the new P-trap and tighten the nuts by hand only. Overtightening can crack the plastic or deform the seal.
Check for Leaks
Run the tap at full pressure. Watch the joints closely. If a drip appears, give the nut a tiny extra turn or check that the washer is sitting flat.
💡 Pro Tips for a Leak-Free Finish
- Hand-tighten only: You rarely need tools for plastic waste fittings.
- New Washers: Never reuse old, compressed washers; always use the ones supplied with the new trap.
- Alignment: Ensure the pipes enter the trap straight. If they are at an angle, the seal will eventually fail.