How to Install a Kitchen Sink Strainer Basket | DIY Leak-Free Seating

Installing a kitchen sink strainer basket means sealing the flange from above and tightening a locknut from below, a job most DIYers finish in under an hour.

A loose or leaking strainer basket is one of the few kitchen repairs that can turn a slow drip into a cabinet full of water. The whole process for how to install a kitchen sink strainer basket comes down to one reliable sequence: seal the top, secure the bottom, reconnect the pipe, and test. You won’t need specialty tools beyond a basin wrench and plumber’s putty, and the steps below work for virtually any standard 3-1/2 inch basket.

Before you start, grab a flashlight and look under the sink, the existing strainer’s locknut is almost always accessible without removing the P-trap entirely.

What You Need for the Job

Gather these items first so you don’t have to stop mid-project. Most of these are standard plumbing supplies you may already have.

• Plumber’s putty — or silicone sealant, depending on your sink material
• Basin wrench — for reaching the locknut in tight spaces
• Adjustable wrench or channel-lock pliers — for the tailpiece nut
• Screwdriver — for removing the old strainer’s basket retainer
• Bucket and rags — for water left in the trap
• Replacement strainer basket — standard size is 3-1/2 inches

The basket size matters more than the brand. Most kitchen sinks in the US accept a 3-1/2 inch strainer, but a few European models use a 90 mm opening, so measure the hole before buying.

Step-by-Step Installation: From Old Strainer to New

These six steps cover the full swap, including removing the old unit. If you’re installing into a brand-new sink, skip step one and start at step two.

Step 1: Remove the Old Assembly

Place a bucket under the trap. Unscrew the slip nuts connecting the tailpiece to the drain pipe, then remove the tailpiece. From above, lift out the basket or lid. From below, loosen the locknut with a basin wrench while holding the strainer body steady from above. Once the locknut and washers drop free, push the old strainer up and out. Clean off every trace of old putty or debris from the sink hole — leftover putty is the most common cause of leaks in a “new” install.

Step 2: Form the Seal Around the Hole

Roll plumber’s putty into a rope about the thickness of a pencil, then press it around the underside of the strainer flange, not around the hole itself. For granite, quartz, or composite sinks, skip the putty and use a clear silicone sealant instead — putty’s oils can stain stone. Press the strainer into the hole from above and twist it lightly to squeeze out excess putty. Keep the strainer centered and level; the flange should sit flush against the sink surface.

Step 3: Assemble the Washers and Locknut From Below

From underneath, slide the parts onto the strainer body in the correct order. Kraus’s installation guide for its ST-4 model specifies a specific sequence: slip on the large rubber washer first, then the fiber washer, then thread the locknut. Some manufacturer instructions call for a foam washer against the sink with the rubber washer below it — check your strainer’s included parts and follow that order. Tighten the locknut with the basin wrench while your helper — or your other hand — holds the strainer body firmly in place from above. Do not over-tighten; snug is correct, and crushing the rubber washer will cause leaks.

Step 4: Trim the Putty and Reconnect the Tailpiece

Wipe away the putty that squeezed out from the flange with a damp cloth. Reattach the tailpiece to the strainer body, then reconnect the trap, tightening the slip nuts by hand until snug, plus a quarter turn. If your strainer has a separate tailpiece that threads into the body, apply a thin layer of pipe thread sealant or wrap Teflon tape on the threads before connecting.

Step 5: Replace the Basket or Lid

Drop the basket into the strainer and give it a half-turn to lock it. If your model uses a stopper, test that it opens and closes smoothly before moving on. For models like the KOHLER K-8799, you’ll also need to reinstall the retaining screw that holds the assembly together — check the manufacturer’s sheet for your specific model.

Step 6: Test for Leaks

Put the drain stopper in or plug the basket, fill the sink halfway with water, then release it all at once. The sudden rush of water is the best leak test there is. Feel underneath around the locknut and tailpiece connections. If anything weeps, tighten that joint a quarter turn and re-test. Most leaks trace back to a missed washer or leftover debris — not to a flaw in the new parts.

Mistakes That Cause Leaks

Three errors cause nearly every failed strainer install, and all are easy to avoid.

• Wrong washer order. The foam, rubber, and fiber washers only seal in the order the manufacturer specifies.
• Not holding the strainer steady. If the body spins while you tighten the locknut, the putty seal breaks and the flange shifts off-center.
• Over-tightening. Crushing the rubber washer deforms it and defeats the seal. Snug is enough.

Choosing the right replacement matters as much as the install itself. Our tested roundup of the best kitchen sink basket strainers covers models from budget stainless picks to KOHLER’s premium units, with the dimensions verified so you buy the right size the first time.

Installation Cheat Sheet

Keep this condensed version for quick reference during the job.

One thing worth checking before you buy: whether your strainer is rated for use with a garbage disposal. Most basket strainers are, but the manufacturer’s spec sheet will say so explicitly — using a non-compatible unit voids the warranty and can back up the drain.

Professional plumbers charge $150 to $300 for this job, but the part itself costs between $15 and $90. KOHLER basket strainers currently list from around $50 up to $93, while solid budget options sit near $15 — either way, you’re saving most of the cost by doing the work yourself.