What You Need to Know Before Starting

Replacing a bathtub drain is a task most homeowners can do in an afternoon with basic tools. The drain assembly sits underneath the tub and connects to your home's plumbing—when it leaks, backs up, or won't hold water, replacement is usually faster than repair. You will need to remove the old drain, clean the opening, and screw in a new one with plumber's putty or a rubber gasket to seal it.

The job requires no special skills, but you do need to know whether your drain is a threaded drain (screws out) or a pop-up drain (lifts out). Most bathtubs have one of these two types. Once you identify which you have, the replacement takes about 30 to 45 minutes.

Key Takeaways

  • Threaded drains unscrew from underneath the tub; pop-up drains lift straight out after you remove the overflow plate.
  • You will need a drain wrench or pipe wrench, a screwdriver, plumber's putty or a rubber gasket, and a bucket to catch water.
  • Always turn off the water supply to your bathroom before you begin, and have a bucket ready because old drain pipes hold standing water.
  • The new drain must match your old one in size and type, or it will not fit the opening or connect properly to the pipes below.
  • Plumber's putty hardens in 24 hours; do not run water through the drain until it has fully set.

Identify Your Drain Type

Look at the drain opening in the bottom of your tub. If you see a visible screw or seam running around the edge of the drain body, you have a threaded drain—it unscrews from below. If the drain has a lever or knob on the overflow plate (the opening on the side of the tub), you have a pop-up drain—the whole assembly lifts out as one piece.

Pop-up drains are more common in modern tubs. Threaded drains are older and more common in cast iron or steel tubs. Knowing which type you have tells you exactly how to remove it and what replacement part to buy. Take a photo of your drain with your phone and bring it to the hardware store, or measure the diameter of the opening with a ruler—most tubs use 1.5-inch or 2-inch drains.

Gather Your Tools and Materials

You will need a drain wrench (a specialized tool with two pins that fit into holes on the drain body) or a pipe wrench if you cannot find a drain wrench. You will also need a screwdriver, a bucket, plumber's putty or a rubber gasket (depending on your drain type), a rag, and a flashlight to see under the tub. If your tub is on a second floor or you cannot access the space below it, you may need to work from inside the tub only.

Buy your replacement drain before you start. Bring the old drain with you to the store, or write down the exact size and type. Mismatched drains will not seal properly and will leak into the walls below your tub.

Remove the Old Threaded Drain

Turn off the water supply to your bathroom at the main shutoff valve. Place a bucket under the drain opening from below the tub (in the basement or crawl space, if you have access). Unscrew the overflow plate on the side of the tub and set it aside.

From underneath the tub, use your drain wrench or pipe wrench to grip the drain body and turn it counterclockwise. The drain will unscrew in one piece. Pull it out and let any standing water drain into the bucket. Use a rag to wipe away old plumber's putty or caulk from the opening—scrape gently so you do not damage the tub surface. Inspect the threads on the underside of the tub opening; they should be clean and free of debris.

Remove the Old Pop-Up Drain

Turn off the water supply. Remove the overflow plate by unscrewing the two bolts that hold it to the tub wall. The overflow plate is connected to a rod that runs down inside the wall and connects to the pop-up stopper mechanism. Pull the overflow plate and rod assembly straight out—it will come free as one unit.

Now you can see the drain body at the bottom of the tub. It will have a threaded collar underneath. Use your drain wrench or pipe wrench to unscrew this collar from below, or grip the drain body itself from above and turn counterclockwise. Once loose, lift the entire pop-up assembly out of the tub. Clean the opening thoroughly with a rag and remove all old putty or gasket material.

Install the New Drain

For a threaded drain, explore a ring of plumber's putty around the underside of the new drain body (about the thickness of a pencil). Press the drain into the opening from above and hold it straight. From below, screw the threaded collar hand-tight, then use your wrench to tighten it another quarter turn. Do not over-tighten—you will crack the tub. Wipe away excess putty with a damp rag.

For a pop-up drain, check whether your new drain uses a rubber gasket or plumber's putty. If it uses a gasket, slide the gasket onto the drain body before inserting it. Insert the drain assembly from above, making sure the overflow connection rod is aligned with the overflow hole in the tub wall. From below, hand-tighten the collar, then use your wrench for a final quarter turn. Reinstall the overflow plate and tighten its bolts.

Test and Wait Before Using

Do not run water through the drain for at least 24 hours if you used plumber's putty—it needs time to harden and create a watertight seal. If you used a rubber gasket, you can test the drain after one hour by filling the tub halfway and watching for leaks underneath.

Once the putty has set, fill the tub and let it drain completely. Watch from below (or have someone check the basement or crawl space) for any drips around the drain connection. A small amount of moisture is normal, but steady dripping means the seal is not tight. If that happens, turn off the water, let the area dry, and tighten the collar another quarter turn.

Frequently Asked Questions

What if I cannot access the space under my tub?

You can still replace a threaded drain from above if the tub is on a second floor or sits over a finished ceiling. Use a drain key (a specialized wrench with a long handle) to grip and turn the drain from inside the tub. You will need to work carefully to avoid dropping the wrench down the drain opening. For pop-up drains, you must access the overflow assembly, which usually requires removing the overflow plate from inside the tub wall.

Can I use caulk instead of plumber's putty?

No. Silicone caulk does not create a watertight seal on threaded drains the way plumber's putty does. Putty is designed to compress and conform to the threads as you tighten the drain. Caulk stays flexible and will eventually allow water to seep through. Use plumber's putty for threaded drains and a rubber gasket for pop-up drains.

What size drain do I need?

Most bathtubs use either 1.5-inch or 2-inch drains. Measure the diameter of your drain opening with a ruler, or take a photo to the hardware store. If you buy the wrong size, it will not fit the opening or thread properly onto the pipes below. The drain size is usually printed on the packaging of the replacement part.

How do I know if my drain is leaking?

Fill the tub and let it sit for 10 minutes without draining. If the water level drops noticeably, the drain is leaking. Check underneath the tub for water drips or stains on the ceiling below. A slow leak may not show up right away, so monitor the area for a few days after installation.

Do I need to replace the overflow plate too?

Only if it is cracked, corroded, or does not fit your new drain assembly. Most overflow plates are interchangeable, but pop-up drain kits sometimes include a new plate. Check the packaging of your replacement drain to see what is included.