Thinking about adding a sink to your kitchen island? It’s one of the most popular kitchen upgrades homeowners are making right now, and for good reason. A kitchen island sink adds a lot of convenience, whether you’re rinsing produce, washing hands between cooking tasks, or just cutting down on trips across the kitchen.
But before you start picking out faucets, there’s some important planning to do. Kitchen island plumbing is a bit more involved than your standard sink installation, and getting the prep work right makes all the difference. Here’s what you need to know before the project gets off the ground.
Step 1: Decide What You Need at Your Island
Before anything else, figure out what you actually want your island to do. Are you adding just a sink? A dishwasher? A garbage disposal? Each of these requires its own plumbing considerations, so it helps to have the full picture from the start.
For most homeowners, the island sink is the main feature—but this is also a great time to think about whether a dishwasher on the island makes sense for your kitchen layout. Planning for both upfront is a lot easier than going back and retrofitting later.
Step 2: Understand What Island Plumbing Involves
Here’s where kitchen island plumbing gets a little different from a standard sink setup. Because your island sits in the middle of the floor—not against a wall—your supply lines and drain line have to run under the floor to reach it.
That means your plumber will need to:
- Run supply lines (hot and cold water) from an existing connection point under the floor to your island
- Install a drain line that connects to your home’s main drain system, also running under the floor
- Ensure proper venting so your drain flows correctly without gurgling or slow drainage
The venting piece is often the trickiest part of a kitchen island installation. Traditional venting runs through the walls and up through the roof, but that’s not an option in the middle of a room. Most plumbers use an air admittance valve (AAV) for island sinks, which allows air into the drain system without needing to run a vent pipe through the floor and ceiling. It’s a well-accepted solution, but it does need to be installed correctly and in compliance with your local building codes.
Step 3: Check Your Home’s Plumbing Layout
Not all homes are set up the same way, and your existing plumbing layout will have a big impact on the scope of this project.
A few things your plumber will assess:
- Where the nearest water supply lines are: Supply lines need to be run to the island, so this determines how much material is needed.
- Your home’s drain slope: Drain lines need to slope downward at the right pitch (typically ¼ inch per foot) to carry waste away properly
- What’s under your floor: Is it a crawl space, a slab, or a basement? This affects how easy (or complex) it is to run new lines.
Homes built on slabs can make this more involved, since running new lines may require cutting through the concrete. It’s worth knowing this before you start budgeting.
Step 4: Think About Your Island Design
Your island’s construction has a real impact on the plumbing installation. A few design details that matter:
- Cabinet space inside the island: Your plumber needs enough room to install the drain, supply connections, and any shutoff valves.
- Sink placement within the island: Centering the sink over where the drain line will run keeps things cleaner and more efficient.
- Island dimensions: Larger islands may need more supply line length, which can affect water pressure if not properly sized.
If you’re having a custom island built, loop in your plumber before the cabinetry is finalized. A quick conversation up front can save you from having to modify the cabinets after the fact.
Step 5: Get Your Permits Sorted
Kitchen plumbing projects sometimes require a permit in Louisiana municipalities. Permitted work is inspected, which protects you as the homeowner and ensures the work is done to code. Unpermitted plumbing can create problems when it comes time to sell your home or file an insurance claim.
Your plumber should be able to pull the necessary permits for you and will know exactly what’s required in your area.
Step 6: Plan for Flooring and Finishing Work
Depending on your floor type, running lines under the floor may require removing and replacing a section of flooring. If you have tile, hardwood, or another finished floor, build this into your project plan and budget.
In some cases, homeowners choose to coordinate the island plumbing with a larger kitchen remodel so everything can be done at once—minimizing disruption and keeping costs down.
Step 7: Call in a Licensed Plumber
This is not a DIY project. Between the permitting requirements, the venting considerations, and the need to tap into your home’s existing supply and drain lines correctly, kitchen island plumbing really needs a licensed, experienced professional.
A skilled plumber will assess your specific setup, give you an honest estimate of the work involved, and make sure everything is installed to code. They’ll also help you avoid the most common mistakes—like improper drain slope or incorrect venting—that can lead to slow drains, gurgling pipes, or even sewer odors in your kitchen.
Ready to Add a Sink to Your Kitchen Island?
Goodbee Plumbing has been helping homeowners across the Northshore and New Orleans area tackle projects like this for over 25 years. Whether you’re in Covington, Mandeville, Metairie, or anywhere in between, our team is ready to walk you through the process and get your kitchen island plumbing done right.
Give us a buzz at 985-893-1883 or contact us to get started with a phone estimate!