Post By Admin
May 5, 2026You probably don’t think much about the P-trap under your sink—until it starts leaking or clogging up.
This curved pipe plays a significant role in keeping sewer gases out of your home, but over time, it can get damaged or blocked.
But, no need to worry. All you need is a quick P-trap swap to fix the problem.
Our guide will break down everything you need to know. But if you’d rather skip the hassle and let the pros handle it, our bathroom renovation service is just a call away!
How Does a P-Trap Work?
The P-trap gets its name from its shape—it looks like the letter “P” when viewed from the side.
It consists of a curved section (like a “U”) connected to a straight pipe that goes into the wall, forming a “P” shape. This design helps trap water, preventing sewer gases from entering your home.
Those gases contain harmful substances like methane and hydrogen sulfide, which can cause bad odours, dizziness, or even health issues with prolonged exposure.
That’s why, holding a small amount of water in its bend will create a seal that blocks these gases from entering your home.
Quick tip: In most Australian homes, it’s common to use P-trap that are made from PVC or chrome-plated metal. The material is known for its lightweight, easier to cut and install, and most consider it as the better option for DIY replacements.
What Should You Prepare Before Replacing a P-Trap?
Before you start replacing your P-trap, gather the right tools to make the whole job a lot easier.
Here’s what you’ll need:
- A bucket or bowl – to catch any leftover water in the P-trap.
- Adjustable wrench or channel-lock pliers – to loosen and tighten slip joint nuts.
- Plumber’s tape – for sealing connections if needed.
- New P-trap kit – ensure it matches your sink’s diameter (usually 1¼ or 1½ inches).
- Gloves – to keep your hands clean.
- Old towel or rags – for wiping up spills.
Prior to getting a replacement for yourself, make sure you have measured the existing P-trap. For kitchen sinks, you can opt for a 1½-inch pipe, while bathroom sinks typically use 1¼-inch.
To save you from uncertainty, bring the old trap with you to the hardware store to make sure everything lines up properly.
Also, before starting, turn off the water supply valves under the sink to avoid any accidental leaks while you’re working.
6 Steps to Replace a P-Trap Under the Sink
Now that you have your tools ready, let’s get into how to change a P-trap under the sink.
1. Place a Bucket Under the P-Trap
First things first, slide a bucket or bowl under the P-trap. This will catch any trapped water or debris, preventing a messy spill.
2. Turn Off the Water Supply & Loosen the Slip Joint Nuts
To turn the shutoff valves under the sink, simply twist them clockwise and wait until they stop. Alternatively, switch off the main water supply to your home if you have difficulty in finding them.
Once you’ve done that, use an adjustable wrench or channel-lock pliers to loosen the slip joint nuts on both ends of the P-trap.
These nuts help secure the trap to the pipe from the sink (also known as tailpiece) and the waste pipe that leads into the wall or floor. Carefully slide them off once they’re loose.
3. Remove the Old P-Trap
Gently pull the old P-trap down and away from the pipes. Be prepared for some water and gunk to come out—this is a great time to check for blockages.
If your sink has been draining slowly, this might also help unblock a sink before installing the new trap.
4. Clean the Pipe Connections
Wipe down the pipe ends with a rag to remove any debris or old plumber’s tape. A clean connection ensures a tight seal and prevents leaks.
5. Install the New P-Trap
Take your new P-trap and align it with the pipes. Slide the slip joint nuts over the connections and hand-tighten them first. Then, use your wrench or pliers to give them a firm—but not overly tight—turn to secure the trap.
6. Check for Leaks
Turn on the sink and let the water run for a few minutes. Watch for leaks around the connections. If you see any drips, slightly tighten the nuts or apply plumber’s tape to create a better seal.
Bonus Tips:
- Unlike kitchen sinks, bathroom sinks usually have smaller P-traps. Double-check the size before buying a replacement.
- If your sink still drains slowly after installation, try unblocking the bathroom sink with a plunger or drain cleaner before assuming there’s another issue.
- If the slip joint nuts are too tight to loosen by hand, wrap a rag around them before using pliers for a better grip without damaging them.
- Avoid flexible P-traps (corrugated tubing). This is because they tend to catch debris more easily and are not compliant with Australian plumbing standards. Our best advice to you is for a longer-lasting and cleaner setup, stick with rigid PVC or ABS.
When Should You Bring In a Plumber?
Replacing the P-trap does not always come as an effective solution to fully solve the issue. So, the moment you run into any of the situations below, it’s best to bring in a licensed plumber:
- The P-trap still leaks post-installation (this could point to a deeper issue with the pipe alignment or seals)
- The pipe inside the wall is cracked or damaged
- You find no accessible shutoff valves under your sink
- Noticing signs of tree root intrusion or ongoing drainage problems
Situations as of the above are likely more than a simple DIY fix. Let us quickly identify the problem and handle any underlying leaking pipes before they turn into repairs that cost massively.
FAQ about P-Trap Replacement
How do you tell if a P-trap is clogged?
If water drains slowly or not at all, your P-trap might be clogged. You may also notice bad odours coming from the drain, which means trapped debris is starting to smell.
Are all sink p traps the same size?
No, sink P-traps come in different sizes. The common sizes for sink are either 1 1⁄2 or 1 1⁄4 inches.
Can you remove the P-trap without turning off water?
Yes, you don’t need to turn off the water supply. Just make sure the faucet is off and place a bucket underneath to catch any trapped water when you remove the P-trap.
How frequently should I get a replacement for my P-trap?
When maintained and installed properly, PVC P-trap can last for decades. As for chrome or brass traps, they may wear out faster (within 5–15 years depending on moisture exposure). It’s best to replace it once you notice any cracks, corrosion, or ongoing leaks.
Is a P-trap different from an S-trap?
Yes it is as P-trap has a horizontal pipe that connects to the wall, while an S-trap runs straight down into the floor. S-traps are no longer compliant under Australian plumbing standards (AS/NZS 3500) since they can lose their water seal. If you already own one, call a plumber nearby and ask them to replace it for you.
I have dealt with a slow-draining sink before, could it be caused by my P-trap?
There’s a possibility. Because the curved section is designed to hold water, it can also trap debris like hair, grease, and soap buildup. So, you can try cleaning the P-trap as a good first step before replacing it.
Conclusion
Now that you know how to replace a P-trap, you can tackle this issue with confidence.
But let’s be honest, not everyone enjoys DIY projects. If you’d rather not deal with leaks, wrenches, and trapped water, there’s no shame in leaving it to the experts.
Skip the hassle and call Neighbourhood Plumbing! Our team will handle any plumbing issues quickly and efficiently.
About the Author
From unclogging the toughest drains to repairing leaking toilets, Ricky is a seasoned plumber who has brought his craftmanship to homes across Melbourne. He is passionate about sharing plumbing tips just as much as he is about fixing your plumbing issues. So, when your taps or pipes begin leaking, you know who to call.
