How to Connect 1 1/4 Sink Drain to 1 1/2 P Trap

When you’re building a new home, it’s important to consider all of the little details. A lot goes into designing and constructing a house, but one detail that may not be on your radar is how to connect 1 1/4 sink drain to 1 1/2 p trap. This blog post will tell you everything you need to know about this process so you can get started right away! 

How to Connect 1 14 Sink Drain to 1 12 P Trap

Why is 1 1/4″ to 1 1/2″ P Trap Important?

The size of your drain matters. The diameter, or width, of the p trap for your sink, is determined by the width of the drain opening on your existing sink. If you’re replacing a current sink with a new one, you’ll likely need to adjust the size of the p trap so they are compatible.

There are many reasons why you may need to connect a 1 1/4 sink drain to a 1 1/2 P Trap, but the most common reason is for new construction. Today’s home designs often call for shallow sinks with small diameter drains and wider countertops. If your drain doesn’t connect to the p trap, you’ll need a new one from your local hardware store.

Materials You Needs:

Materials You Needs
  • 1 1/4 inch drain pipe
  • 1 1/2 inch p trap
  • Measuring tape
  • Utility knife
  • Pencil
  • Teflon tape or pipe dope (optional)  
  • 1 pair of pliers (not shown)

Instructions On How to Connect 1 1/4 Sink Drain to 1 1/2 P Trap

1. Measure the length of the new section of piping you are putting it, from where it turns downwards to where it will be connected with the P Trap you have already installed. There should be at least 1 1/2 inches between these points, and if you want to make sure there is, add another inch for good measure.

Measure the Length

2. On the open end of the piping, which goes down towards your drain that’s already installed, drill a hole big enough to fit the P Trap Adapter Fitting through it.

3. Place the adapter fitting in with the rubber gasket facing downwards and screw it into place using a wrench.

4. Attach your new section of piping by connecting it to the P Trap Adapter Fitting. Tighten in a clockwise direction only, and this ensures that you won’t be able to tighten it further once everything is in place.

5. Now, we will work on the open end of your new section of piping that you connected to the P Trap Adapter Fitting, measure 1 inch below the opening, and drill a hole big enough for another adapter fitting (if you can manage to leave this one out it would be ideal, but not always possible).

6. Insert the P Trap again with the rubber gasket facing downwards and attach it to the new piece of piping you just connected, tighten in a clockwise direction only.

7. In order to connect your new section of piping that leads from underneath your sink into the drainpipe that is already installed, unscrew both of these screws from the P Trap Adapter Fitting and attach the Flexible Dishwasher Connector to it and tighten in a clockwise direction.

8. Now, let’s work on the flexible dishwasher connector while holding onto this section of piping. Pull upward to connect it with your new section underneath your sink and allow it enough room so that you can add the rubber washer and then twist, unscrew the screws on your P Trap Adapter Fitting, attach it with the rubber gasket facing downwards, and tighten in a clockwise direction only.

9. Once you have done this with both pieces of piping, attach your new section to the opening of these water lines by unscrewing them slightly, aligning them correctly, and screwing them tightly into place.

10. Test to see if all of the connections are tight and that there is no leakage whatsoever, turn your water on and check again for leaks making sure everything is firmly in place. Once you feel confident that they’re all right, you’re done with this project.

Test to See All Connections

You Can Check It Out to Remove Sink Drain Pipe Coming Out of Wall

Tips and Suggestions

  • If you are adding extra piping to your sink drain, use 1 inch for every additional foot of piping.
  • Always remember to use Teflon tape or pipe dope when connecting P Trap Adapter Fitting with other pieces of pipings to ensure no leakage will occur over time.
  • Remember that this project may take longer than the estimated amount given. It all depends on your level of skill and experience. Plus, if you’re a newbie, always remember to take it slow and easy.
  • In case you have to buy any materials or tools, always check your local hardware store for better deals.
  • When connecting the P Trap Adapter Fitting with other pieces of pipings, make sure it’s tight, and there’s no leakage whatsoever before proceeding to the next step.
  • Always read the manufacturer’s instructions on how to use this specific tool before using it.
  • Read the warning and safety labels on every tool before using them to ensure you have a safe experience when working with tools.
  • Always work in a well-ventilated area to keep yourself away from fumes, chemicals, and other hazardous materials that may be released during this project.
  • Never forget to wear protective gear like gloves, eye goggles, and a mask in case you’re working with hazardous materials.
  • If you’re adding an extra piece of piping to your sink drain, make sure you add the dishwasher connector as well for proper drainage.
  • When installing additional piping underneath your kitchen sink, make sure there’s enough room for it.
  • Before drilling a hole in your kitchen sink, always make sure to use a center punch first in order to create a starting point.
  • When you’re connecting the dishwasher connector with your new piece of piping, insert this section into your sink drain and twist it clockwise.


The answer is simple for those wondering how to connect 1 1/4 sink drain to 1 1/2 p trap. First, you will need an adapter that includes a pop-up stopper. Your sink trap contains several different components. The most important of these is the p-Trap. This is located beneath your sink with a bend to hold water and prevent sewer gases from entering your home. If you only have a 1 1/4 inch drain, then it will be necessary to install a trap adapter to achieve a water-tight connection with your existing p-trap. Thank you for reading our article; if you have any questions or concerns, please comment below.

You may also check it out: How to Plumb a Double Kitchen Sink With Disposal and Dishwasher

Smart Home Pick