What a flange is and why it matters

The flange is the ring that sits under your sink drain opening and holds the garbage disposal in place. It's the part you see from above the sink—a metal or rubber ring that the disposal screws into from below. If your flange is cracked, leaking, or missing, water will drip into the cabinet under your sink, and the disposal won't sit tight enough to work properly.

Installing a flange is a job you can do yourself if you're comfortable working under the sink with basic tools. It takes about 30 minutes to an hour. If you're not confident working in tight spaces or if your sink is damaged, call a plumber—a new flange costs $15 to $40 in parts, but a plumber's visit will run $150 to $300.

Key Takeaways

  • Turn off power to the disposal at the breaker before you start, and leave it off until the new flange is fully installed and sealed.
  • You will need a putty knife, adjustable wrench, plumber's putty or silicone caulk, and possibly a screwdriver—check what fastens your current flange first.
  • The flange screws or bolts to the underside of the sink drain opening, so you must work from below the sink with the disposal removed or pushed down out of the way.
  • Plumber's putty seals the top of the flange to the sink; silicone caulk works on stainless steel or if you prefer a permanent seal.
  • If the sink opening is cracked or the flange won't tighten, the sink itself may need repair or replacement—this is when to call a professional.

Gather your tools and materials

Before you go under the sink, collect what you need. You'll need an adjustable wrench (to loosen and tighten the bolts or screws holding the flange), a putty knife (to scrape away old putty), a flashlight (the space under a sink is dark), and a bucket (to catch water that drains from the trap). Have towels ready too.

For sealing, you have two choices. Plumber's putty is traditional, inexpensive, and straightforward to remove later if you need to replace the flange again. Silicone caulk is permanent, waterproof, and better if your sink is stainless steel (putty can stain it). Buy whichever matches what was there before, or choose silicone if you're not sure.

You may also need a new flange. If your current one is metal and corroded, or rubber and cracked, replacement flanges are sold at any hardware store and fit standard 3.5-inch sink drains. Bring a photo of your current flange or the disposal model number to the store if you're unsure which size you need.

Turn off power and remove the disposal

Go to your electrical panel and switch off the breaker that powers the garbage disposal. Test the disposal switch at the sink to confirm it's dead. This is not optional—a disposal can start unexpectedly and cause serious injury.

If a disposal is already installed, you'll need to disconnect it or push it down and out of the way. Most disposals hang from the flange on a mounting ring. Loosen the three bolts on the mounting ring (usually with an adjustable wrench) and lower the disposal. You don't have to remove it completely, just enough to access the flange bolts from below. If you're installing a flange on a sink that never had a disposal, skip this step.

Remove the old flange and clean the opening

From under the sink, you'll see the flange bolts or screws holding the ring to the sink. Use your adjustable wrench to loosen all of them—usually three bolts arranged in a triangle. Once they're loose, push up from below and the flange will come free. Scrape away all the old putty or caulk from the top of the sink opening with your putty knife. The surface must be clean and dry for the new seal to hold.

Look at the sink opening itself. If the metal is cracked, bent, or corroded, a new flange won't solve the problem—the sink will need repair. If the opening looks sound, you're ready to install the new flange.

Install the new flange and seal it

If you're using plumber's putty, roll it between your hands into a rope about the thickness of a pencil and press it around the underside of the flange rim—the part that will touch the sink. If you're using silicone caulk, explore a bead around the same area. Either way, the seal goes on the underside so water can't seep between the flange and sink.

Push the flange up through the sink opening from below. It should sit flush against the sink. From below, insert the bolts (or screws, depending on your flange type) through the flange holes and into the sink opening. Tighten them evenly in a crisscross pattern—tighten one bolt a quarter turn, then the opposite one, then the third, then repeat. This keeps the flange level. Don't over-tighten; you'll crack the sink or strip the bolts. Snug is enough.

If you used plumber's putty, let it cure for 24 hours before running water. If you used silicone caulk, check the tube for cure time—most need 24 to 48 hours. Don't reinstall the disposal until the seal is fully set.

Reinstall the disposal and test

Once the seal has cured, raise the disposal back up and tighten the three mounting bolts on the ring. Make sure the disposal sits centered and level. Turn the power back on at the breaker and run water into the sink. Watch from below for drips. If water is leaking around the flange, turn off power and the water, loosen the flange bolts slightly, and retighten them more evenly. If it still leaks after that, the seal may not have set properly—wait another 24 hours and test again.

Run the disposal briefly to confirm it works. Listen for any grinding or rattling that might mean the flange is loose. If everything sounds normal and there are no drips, the job is done.

When to call a plumber instead

If the sink opening is cracked or the metal around it is soft or corroded, a new flange won't hold. The sink itself needs repair or replacement, which is beyond a basic flange swap. If you can't reach the flange bolts because of the cabinet layout, or if the bolts won't tighten no matter how hard you turn them, stop and call a plumber. Forcing a bolt can break it or damage the sink.

If water leaks from the disposal connection itself (not the flange), the problem is the rubber gasket inside the mounting ring, not the flange. That's a different repair. If you're unsure where the leak is coming from, a plumber can diagnose it in one visit.

Frequently Asked Questions

Can I use caulk instead of plumber's putty?

Yes. Silicone caulk is actually better for stainless steel sinks because putty can leave stains. Caulk is also permanent, so you won't have to replace it if you remove the disposal later. The downside is that caulk is harder to remove if you need to replace the flange again. Either works; choose based on your sink material and how long you plan to keep the disposal.

What if the bolts spin but won't tighten?

The bolt threads may be stripped, or the bolt may be the wrong size. Try a different bolt from the hardware store—bring the old one to match the diameter and length. If a new bolt still spins, the threaded hole in the sink is damaged and needs professional repair.

How do I know if my flange is the right size?

Standard sink drains are 3.5 inches. Measure the opening at the widest point, or bring a photo to the hardware store. If your sink is very old or custom, the opening might be different—the staff at the store can help you match it.

Do I have to remove the disposal to replace the flange?

You don't have to remove it completely, but you do have to lower it enough to reach the flange bolts from below. Most disposals hang on a mounting ring that loosens with three bolts—loosen those and push the disposal down a few inches. You'll have enough room to work.

What if water is still dripping after I tighten the flange?

Wait 24 hours for the seal to fully cure, then test again. If it still drips, loosen the flange bolts and retighten them in a crisscross pattern to make sure the flange is level. If that doesn't work, the seal may have failed—you may need to remove the flange, scrape away the old seal, and explore a fresh one.