The humble sink trap is a part of everyday plumbing systems. So how do you install one beneath your bathroom basin? Well, in this guide we’ll explain how and why they’re vital to your plumbing for the bathroom. You’ll also find advice on what you need to do to install a bathroom sink in place for a useful and supportive system.

Table of contents

What is a sink trap?

You might also be asking yourself “What is a bottle trap?”. Sink traps and bottle traps are the same thing, just with different names. So, to answer both questions we’ll be referring to them as sink traps from here on.

Sink traps are an essential part of basin plumbing, attached to the waste plug under the sink. It is used to help keep your bathroom hygienic and defend against bacteria. Sink traps can also prevent harmful gasses from rising up through the drainage system below the home and entering through the waste.

Many sink traps also come with a removable filter. A useful feature that is used to help block items from making their way down the drain. Maybe items like rings, earrings or other items that you’ve accidentally found yourself dropping down the sink!

How to install a bathroom sink drain trap

When installing a bathroom sink trap, you’ll typically be able to find a trap with the essentials for fitting. So, when you get your sink trap, ensure the following is included. If not, purchase separately:

  • Sink trap main body
  • Outlet pipe
  • Outlet pipe wall cover
  • ‘Top hat’ washer
  • Tapered seal
  • Silicone sealant

Now onto the fitting!

1. Fit the waste to the sink trap.

Place the ‘top hat’ washer inside the threaded top flange. This ensures a secure seal when the waste plug is screwed to the sink trap.

2. Put the waste pipe attachments together.

Fit the tapered seal, tapered end first, into the sink trap’s body. You can now insert the outlet pipe into the sink trap, making sure the waste outlet pipe is horizontal from the sink trap.

Note: If the length is excessive, you can shorten it as needed.

3. Fit the pipe to the mains drain system

Use the pipe cover to conceal connections from view, ensuring it sits flush with the wall. Use silicone sealant if you want a more secure covering.

Note: There is no fixing method for the pipe cover because of its flush sitting and might not be needed. Use your judgment to choose whether the pipe cover is needed.

When you return the basin and accessories, be careful in doing so. Avoid damaging the finishes and fittings, keeping the bathroom furniture clean regularly with a soft, damp cloth. Do not use abrasive cleaning chemicals or detergents as these can cause deterioration.

What is a P trap?

Another style of trap is the plumbing trap. The curved pieces of drainpipe underneath your sink and basin often referred to as P traps, do a lot of dirty work. Over time they crack, leak, become corroded or get plugged with years of amassed soap and grease.

This section will explain how to change a plumbing trap. Before we move on, it’s important to remember that when replacing a plumbing trap, you should use the same type of trap you remove. For example, use plastic for plastic.

How to change a plumbing trap

1. Turn off the water stops.

This is so that no one can turn on the tap while the trap is being removed. Make sure there is a clear work area and place a bucket under the trap to catch water.

2. Inspect the trap.

If there is a nut located on the lowest part of the inverted ‘P’, unscrew it with a pair of pliers. Let the water drain out into the bucket.

3. Unscrew the nuts holding the P trap by hand.

Grip the trap tight with one hand and turn each nut counterclockwise until they start to loosen. You must unscrew two nuts to remove the trap.

4. Remove the P trap.

Push the fixings out of the way, pulling down on the section of the trap connected to the tailpipe. If the trap is still full, place the bucket under the trap opening before you attempt this. Once that end of the trap is free, the other end should pull away from the drainpipe with little effort.

5. You can now install your new P trap using the nuts provided.

Once installed, turn the water back on and give it a test. Ensure that you continue to complete regular maintenance on your drainage system.

Plumbing Waste Pipe Trap P Shaped Outlet Trap

Need more plumbing supplies? Explore our range at Plumbing Superstore. For additional questions on other products or projects, check out our other range of help and advice or contact our friendly customer service team for support.

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