How To Vent A Kitchen Sink Under A Window? (8 Step Guide)

Last Updated On May 26, 2022
how to vent a kitchen sink under a window

Do you need to vent your kitchen sink, but there is a window in the way? Many homeowners like to look out the window when they wash dishes and prep for dinner. It also provides natural light, brightening up the appearance of the kitchen. 

However, the delightful window can make kitchen sink ventilation more difficult since you can’t use the traditional vent line. 

In this PlumbingNav guide, we will cover:

  • What you need to know about venting a kitchen sink under a window
  • Supplies you’ll need to vent a kitchen sink under a window
  • How to vent a kitchen sink under a window

What's In This Guide?

      What You Need To Know About Venting A Kitchen Sink Under A Window

      All kitchen sinks require a sink vent according to the international plumbing code.         

      Proper plumbing ventilation prevents trap seal loss, material deterioration, and flow retardation.       

      Trap seal loss occurs when the P-trap or the S-trap of a fixture loses a proper seal. Trap seal loss occurs due to:

      • Siphonage
      • Back pressure
      • Evaporation
      • Capillary attraction
      • Wind effect      

      Corrosion occurs naturally over time, especially when plumbing encounters hot temperatures and high water pressure. Plumbing ventilation can also prevent material deterioration thanks to corrosion since the airflow helps dry out your plumbing properly. Corrosion will also create drinking water problems.     

      Water flow retardation occurs for a number of reasons and can lead to a stubborn sewer line clog or allow sewer gas to get into your home. 

      How Plumbing Ventilation Works

      Your plumbing system’s ventilation system connects your plumbing pipes to your home’s main ventilation system using a vent pipe or vent stack, in which the air in your pipes is ventilated up through your home and out the roof. No water flows through the plumbing vent.

      It’s important to encourage proper airflow using an upward slope. However, what do you do if a window prevents you from creating the proper upward slope? Learn what to do below.

      Air Admittance Valve

      An air admittance valve (AAV) is an alternative plumbing ventilation method that doesn’t require a connection to your home’s main ventilation system, making them easy to install. Air admittance valves are accepted according to most municipal plumbing codes, but they don’t provide as effective a solution.

      did you know how to vent a kitchen sink under a window

      Supplies You’ll Need To Vent A Kitchen Sink Under A Window

      PVC Plumbing Vent Pipe

      The first thing you will need when venting a kitchen sink under a window is a vent pipe. Most vent pipes are made from PVC plastic or PEX plastic. While PVC plastic and PEX plastic may not work for all plumbing applications, the inexpensive material works well for air ventilation. A vent pipe for your kitchen sink should not be smaller than 1.5” in diameter to prevent clogs. 

      PVC Sanitary Tee

      A sanitary tee, or elbow, is a plumbing fixture that allows you to connect your plumbing system to your ventilation system, and it works in a similar fashion as a splitter. It’s generally made out of PVC plastic. The sanitary tee you will use for a regular kitchen sink will have two 2” openings with an additional 1.25” port.  

      PVC Cement 

      PVC cement is a sealant that attaches PVC pipe together to ensure you don’t experience a leak. It works using chemicals that melt the surface of both materials then harden to ensure an airtight connection. You must use PVC according to the instructions or it can possibly allow the chemicals to infiltrate into your drinking water and create a foul odor. 

      Hack Saw

      A hack saw is a type of saw that can easily cut through PVC pipe. You can use a manual hack saw, which will require more effort on your part, or you can use a powered hack saw if you have one available. 

      Power Drill 

      You will need a power drill to allow you to drill into the kitchen wall and feed the ventilation pipe at the proper locations. 

      How To Vent A Kitchen Sink Under A Window (8 Steps)

      Venting a kitchen sink under a window is similar to venting a kitchen sink without a window but with extra considerations to accommodate for the window. Follow this simple guide to vent a kitchen sink under a window yourself. 

      Step 1: Prep 

      Clean your sink and remove all items that may get in your way. You will need access to the plumbing in the kitchen sink cabinet. 

      Locate the shutoff valve for your kitchen sink and use it to prevent water from flowing to your kitchen sink while you work.  

      Step 2: Attach Sanitation Tee

      You will now attach the sanitary tee to your drain pipe, or drain line, using PVC cement with the 1.25” port facing upward. Ideally, you don’t want to attach it more than 3.5’ from the P trap. 

      Step 3: Add PVC Pipe to Opening

      Use your hack saw to cut 2” of PVC pipe 1.5” in diameter and attach it to the opening of the elbow that is facing upward. 

      Step 4: Configure Ventilation Placement

      With the window in the way, you can’t attach the ventilation pipe to the ventilation system as normal since you need to create an adequate slope. 

      Use chalk to draw a vertical slope around your window at a rate of ¼” per foot until you get past the window to your vertical pipe, also known as your ventilation stack.  

      Step 5: Drill Holes in Studs 

      Drill holes through your chalk line wherever you can find a stud, also known as a load-bearing beam. You want to drill the holes into the studs so that you don’t compromise the integrity of your kitchen walls. 

      Most walls have a stud every 16 – 24 inches. You can find the studs in your wall using a stud finder or tapping on the wall. 

      Use a drill bit 1.75” in diameter. 

      Step 6: Feed Vent Piping Upwards 

      Feed your horizontal pipe through the holes you drilled into the wall and connect using an elbow at each hole. 

      You may need to feed vertical pipe up to your attic to finally reach the vent stack. This may require you to drill through your ceiling plate and feed the pipe accordingly. 

      Step 7: Attach Vent Pipe to Vent Stack

      When you find a convenient location, attach the sanitary tee to the vent stack using PVC cement. 

      You will then use a horizontal pipe to connect the vent pipe to the vent stack. 

      At this time, you should be completely ventilated. Restore water to your kitchen sink and check the vent to ensure everything works properly. 

      Step 8: Clean Up

      Clean up any dust you created throughout the process and cover any holes. 

      FAQs For How To Vent A Kitchen Sink Under A Window 

      Does a kitchen sink drain need to be vented?

      Yes, according to the building code applicable in 49 states, you need to vent your kitchen sink drain. 

      Should a kitchen sink be under the window?

      A window above the kitchen sink allows natural light to enter your home and gives you something to look at when you clean up after dinner. 

      How do you vent under a sink?

      To vent under a sink, you add ventilation piping to your vent stack in a horizontal direction around the window. 

      How far does a vent need to be from a window?

      The vent should be able to go around the window at a horizontal slop of ¼” per foot.

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      About Plumbing Navigator

      We write about "all things plumbing," helping you navigate common questions, repairs, and the best plumbing products on the market.

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      We write about “all things plumbing,” helping you navigate common questions, repairs, and the best plumbing products on the market.

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