What you're replacing and why it matters

A bathtub drain has two visible parts and one hidden one. The drain cover (or strainer) sits on top and catches hair. Below that is the drain body—a brass or plastic fitting that screws into the tub. Underneath, inside the wall, is the drain pipe that carries water away. When you replace a drain, you're usually replacing the body and cover together as a unit, which takes about 30 minutes if you have basic tools.

Drains fail for three reasons: the rubber gasket inside cracks and water leaks into the wall, the threads corrode and the cover spins without tightening, or the drain body itself cracks. If water pools around the base of the tub or drips into the cabinet below, the gasket has failed and replacement is the real fix—caulking over it is temporary.

Key Takeaways

  • You need a drain wrench (a specialized tool, about $8 to $15) or a large adjustable wrench to unscrew the old drain body from inside the tub.
  • The drain body screws into the tub from underneath, so you'll need access from below—either from a basement, crawl space, or by removing the panel under a built-in tub.
  • New drain kits come with the body, cover, gasket, and putty, and cost $15 to $40 depending on material and finish.
  • If you cannot access the drain from below, or if the old body is stuck, you may need to call a plumber rather than force it and crack the tub.

Gathering tools and the right replacement drain

Before you start, buy a new drain kit that matches your tub material. If your tub is cast iron or steel, get a metal drain body. If it's acrylic or fiberglass, a plastic body works fine and costs less. The kit should include the drain body, the strainer cover, a rubber gasket, and plumber's putty. Bring a photo of your old drain to the hardware store if you're unsure about the size—most are 1.5 inches in diameter, but some older tubs use 1.25 inches.

Gather these tools: a drain wrench (a flat tool with two pins that fit into holes on the drain body), a large adjustable wrench as a backup, a screwdriver, a bucket, and a flashlight. If you don't own a drain wrench, rent one from a tool rental counter for a few dollars or buy one—you'll use it again. Do not try to unscrew the drain with pliers; you'll strip the body and make the job harder.

Accessing the drain from below

The drain body screws into the tub from underneath, so you must reach it from below. If your tub sits over a basement or crawl space, go down there with your flashlight and look up at the tub bottom. You'll see the drain body sticking down. If your tub is on a second floor or over a finished room, look for an access panel—usually a removable piece of drywall or wood in the wall or cabinet directly under the drain. If there's no panel and no space below, you have a problem: the tub may be set in concrete or the wall is sealed. In that case, stop and call a plumber; forcing the drain from above can crack the tub.

Once you're below the tub, place your bucket under the drain to catch water that will spill when you unscrew it. Have your flashlight ready so you can see what you're doing.

Removing the old drain body

From below, insert the drain wrench into the two holes on the drain body and turn it counterclockwise. If the drain wrench doesn't fit, use a large adjustable wrench on the flat part of the body itself. Turn slowly and steadily; if it won't budge after a few seconds of firm pressure, stop. Forcing a stuck drain can crack the tub or break the fitting inside the wall. Spray the joint with penetrating oil (like WD-40), wait 15 minutes, and try again.

Once the body turns, unscrew it by hand until it comes free. Water will drip—that's normal. Lift the old body out and set it aside. From inside the tub, you can now pull out the old strainer cover. Scrape away the old putty around the drain hole using a scraper or old chisel.

Installing the new drain body and gasket

Roll a rope of plumber's putty about the thickness of a pencil and press it around the underside of the new drain body where it will touch the tub. This putty seals the gap and prevents water from leaking into the wall. Don't use caulk—putty is removable and won't harden, so the next person can replace the drain without chiseling.

Slide the rubber gasket onto the threads of the new drain body. From inside the tub, insert the body into the drain hole and push it down firmly so the putty spreads evenly. From below, thread the body back into the fitting inside the wall by hand first, then use the drain wrench to tighten it. Tighten firmly but not with all your strength—you want a watertight seal, not a crushed gasket. Wipe away excess putty from inside the tub with a damp cloth.

Attaching the strainer cover

The strainer cover screws onto the top of the drain body. Align the cover so the handle points the direction you want it, then turn it clockwise by hand until it's snug. Do not overtighten—the cover should be tight enough that it doesn't spin when you pull on it, but loose enough that you can unscrew it by hand later. If you strip the threads by forcing it, you'll have to replace the whole body again.

Run water in the tub and let it drain. Watch from below for drips around the drain body. If water leaks, the gasket may not be seated properly. In that case, you'll need to unscrew the body, check that the gasket is in place, and reinstall it.

When to call a plumber instead

Call a plumber if the old drain body won't unscrew after you've applied penetrating oil and waited, if you cannot access the drain from below, if water continues to leak after you've reinstalled the new body twice, or if you see cracks in the tub around the drain hole. Forcing a stuck drain or trying to work around a sealed tub can cause damage that costs far more to repair than hiring help from the start.

A plumber can also help if the drain pipe inside the wall is cracked or if the fitting that the body screws into is damaged. These are problems you can't see until the body is out, and they require different repairs than a straightforward drain replacement.

Frequently Asked Questions

Can I replace a drain without access from below?

Not safely. The drain body screws in from underneath, and trying to unscrew it from above will damage the tub. If there's no basement, crawl space, or access panel, a plumber may be able to cut an access hole in the wall or work from a different angle, but this is beyond a DIY job.

What if water still leaks after I install the new drain?

The gasket may not be seated evenly, or the body may not be tight enough. Unscrew the body, check that the gasket is sitting flat on the threads, and reinstall it. If it still leaks, the drain pipe fitting inside the wall may be damaged, and you'll need a plumber to inspect it.

Do I need to turn off the water before replacing a drain?

No. The drain carries water away from the tub; it doesn't bring water in. You can work on it with the water on. Just make sure the tub is empty before you start.

How long does a new drain last?

A properly installed drain with a good gasket usually lasts 10 to 20 years. The gasket will eventually crack from temperature changes and movement, but the body itself can last much longer if it's not forced or damaged during removal.

Can I use silicone caulk instead of plumber's putty?

No. Caulk hardens and bonds permanently, so the next person who needs to replace the drain will have to chisel it out, which risks damaging the tub. Putty stays soft and removable, making future replacements easier.