Drain Strainer — Kitchen Sink Basket Drain Assembly Guide

A drain strainer is a basket-style drain insert that sits in a kitchen sink drain opening to catch food particles and debris while allowing water to pass through, and connects to the tailpiece below as the starting point of the drain assembly.

Drain Strainer (Kitchen Sink Strainer) diagram — labeled parts, dimensions, and installation context

What It Is

A drain strainer consists of the strainer body — a flanged cup that fits into the sink drain hole — and a removable basket that catches solids. The flange sits on top of the sink surface, sealed with plumber's putty or a gasket. The body threads into a locknut from below the sink, clamping the assembly to the sink deck. The lower end of the body accepts a tailpiece via a slip-joint nut.

The strainer is both a functional filter and the structural anchor for the kitchen drain assembly. A loose or improperly sealed strainer body is one of the most common sources of under-sink leaks, particularly around the flange where it meets the sink surface.

Types

Strainer bodies are available in stainless steel and chrome-plated brass. Basket styles include lift-and-clean and twist-to-lock. Some include a built-in stopper for filling the sink. Deep-cup variants for garbage disposals are a separate category with a different mounting system.

Where It Is Used

Drain strainers are used in kitchen sinks, utility sinks, bar sinks, and laundry sinks. They are not used in bathroom lavatories, which use a pop-up drain instead.

How to Identify One

The strainer is the perforated cup visible in the kitchen sink drain opening. It can be lifted out for cleaning. The mounting hardware underneath the sink consists of a rubber gasket, friction ring, and locknut threaded onto the strainer body.

Replacement

Replace a drain strainer when it corrodes, the basket no longer seals, the strainer body leaks at the flange, or when upgrading a sink. Installation requires removing the locknut from below — a basket wrench or locknut wrench simplifies this. Putty or a gasket seals the new flange. No permit is required.

Drain Strainer (Kitchen Sink Strainer) — FAQ

Why is water leaking under my kitchen sink at the drain?

The most common cause is a failed seal between the strainer flange and the sink surface — typically old or missing plumber's putty, or a cracked strainer body. Remove the strainer and reseal it with fresh putty or the manufacturer's gasket.

Can I use silicone instead of plumber's putty on a drain strainer?

Silicone works but is harder to remove later. Plumber's putty is traditional and preferred for most metal sinks. Check the strainer manufacturer's instructions — some composite or solid-surface sinks require silicone or a gasket instead of putty.

What size drain strainer fits my kitchen sink?

Most kitchen sinks have a standard 3-1/2-inch drain opening, and standard strainers are designed for this size. Confirm your opening before purchasing — some older or specialty sinks may differ.

How do I tighten a loose drain strainer from below?

Use a basket wrench or a large locknut wrench to tighten the locknut onto the strainer body from under the sink. Hold the strainer basket with a screwdriver through the crossbar to prevent it from spinning while you tighten.

How often should I replace a drain strainer?

A quality stainless strainer can last the life of the sink with basket replacements. Replace the full assembly when the body corrodes, the flange seal fails repeatedly, or the threads are stripped.