What you need to know before you start

A bathtub drain replacement is a job most homeowners can do in an afternoon with basic tools. The drain assembly sits underneath the tub and connects to your home's plumbing line. You will need to remove the old drain, clean the opening, and install a new one using plumber's putty or caulk to seal it. The whole process takes two to four hours depending on how corroded the old drain is and whether you hit any complications underneath.

Before you begin, turn off the water supply to the bathroom if you can locate the shutoff valve. If you cannot find it, you should know where your home's main water shutoff is located in case something goes wrong. You do not need to drain the tub first — the drain itself holds very little water — but have towels ready because water will spill when you disconnect the drain trap underneath.

Key Takeaways

  • You will need a drain removal tool (or a large pipe wrench), plumber's putty or silicone caulk, a new drain assembly, and basic hand tools like a screwdriver and adjustable wrench.
  • The drain sits in two parts: the visible trim ring on top of the tub and the threaded pipe underneath that connects to your plumbing line.
  • Most old drains unscrew by turning counterclockwise from underneath the tub, though some are glued in place and require cutting or prying.
  • After removing the old drain, you must clean away all old putty and debris before installing the new one, or it will leak.
  • The new drain needs plumber's putty around the threads to seal it; silicone caulk works but takes longer to cure and is harder to remove later.

Gather your tools and materials

You will need a drain removal tool (a specialized wrench that costs $8 to $15 at any hardware store) or a large pipe wrench if you already own one. A drain removal tool has two pins that fit into holes on the drain collar, making it much easier to turn than a wrench. You will also need an adjustable wrench to disconnect the trap underneath, a screwdriver (usually flathead), a putty knife or old butter knife to scrape away old putty, and a bucket to catch water.

For materials, buy a new drain assembly (the complete kit costs $15 to $40 depending on finish and quality), a container of plumber's putty, and either a rag or sponge for cleanup. Plumber's putty is the standard choice because it stays pliable, does not harden, and is easy to remove if you need to service the drain later. If you prefer silicone caulk instead, buy 100% silicone caulk rated for bathrooms — not acrylic latex caulk, which will fail in a wet environment.

Remove the old drain from underneath the tub

The drain assembly has two parts: the trim ring (the visible piece on top of the tub) and the threaded pipe underneath. You will work from below. If your tub is on a second floor or you cannot access underneath, you may need to remove the ceiling panel below or work from a basement if the tub is against an outside wall. Shine a flashlight up into the drain opening to see what you are working with.

Place your bucket underneath the drain trap to catch water. Use your adjustable wrench to loosen the slip nut (the large nut that connects the trap to the drain pipe) by turning it counterclockwise. Once it is loose enough, unscrew it by hand and pull the trap down. Water will spill — this is normal. Set the trap aside.

Now look at the drain collar (the threaded part that sticks up into the tub). Use your drain removal tool or pipe wrench to grip it and turn counterclockwise. If the drain is old, it may not budge at first. Apply penetrating oil (like WD-40) and wait 15 minutes, then try again. If it still will not turn, the drain may be glued in place. In that case, you will need to cut it out using a reciprocating saw or hacksaw, which is slower but still manageable. Once the old drain is out, scrape away every bit of old putty from the opening using your putty knife.

Install the new drain with a proper seal

Roll a rope of plumber's putty about the thickness of a pencil and press it around the threads of the new drain pipe. Do not use too much — a thin, even ring is all you need. The putty fills the gaps and prevents water from seeping down around the drain. If you are using silicone caulk instead, apply a bead around the threads, but know that it will take 24 hours to cure fully and you cannot use the tub during that time.

Insert the new drain into the opening from above and screw it down by hand as far as it will go. Then, from underneath, use your drain removal tool or wrench to tighten it another quarter turn. Do not over-tighten — you only need it snug enough that it does not move. Excess pressure can crack the tub or strip the threads. Wipe away any putty that squeezes out around the trim ring using a damp rag.

Reconnect the trap and test for leaks

Slide the trap back up and hand-tighten the slip nut onto the drain pipe. Use your adjustable wrench to snug it another quarter turn. Again, snug is the goal — over-tightening can crack plastic traps or strip metal threads. Turn the water back on and run water down the drain for 30 seconds while you watch underneath for drips.

If water drips from the slip nut connection, tighten it slightly more. If water seeps around the drain collar where it meets the tub, you did not use enough putty or did not clean away old putty completely. In that case, you will need to remove the drain again, clean the opening thoroughly, and reinstall with fresh putty. If water leaks from inside the trap itself, the trap is damaged and needs replacement.

Common problems and how to fix them

If the old drain will not unscrew, do not force it — you risk cracking the tub or stripping the threads. Apply penetrating oil and wait several hours or overnight. If it still will not move, use a reciprocating saw or hacksaw to cut the drain pipe just below the tub. You can then unscrew what remains from underneath. This takes longer but avoids damage.

If you see water pooling underneath the tub after installation, the most common cause is old putty left in the opening. The new putty cannot seal properly if it is not in direct contact with clean surfaces. Remove the drain, scrape the opening completely clean, and reinstall. A second common cause is over-tightening the trap connection, which can crack plastic fittings. Loosen it slightly and see if the leak stops.

If the drain leaks only when you first run water, wait a few minutes. Air trapped in the new putty can create small bubbles that seal as water pressure pushes the putty into place. If the leak continues after five minutes of running water, the seal is not working and you need to remove and reinstall the drain.

When to call a plumber instead

If the drain opening is cracked or the tub itself is damaged, a new drain will not seal properly and you need professional repair. If you cannot access the space underneath the tub (such as in a mobile home or a tub built into a sealed platform), a plumber has specialized tools and techniques to work around this. If the old drain is so corroded that cutting it out damages the surrounding pipe, or if you discover the drain line itself is cracked or leaking, those are plumbing problems beyond a simple drain swap.

If you are uncomfortable working with tools or do not have access to the space underneath your tub, a plumber can complete this job in one to two hours. The cost is typically $150 to $300 in labor plus the cost of the drain assembly itself.

Frequently Asked Questions

Can I replace a drain without accessing the space underneath?

Not easily. You need to disconnect the trap and unscrew the drain collar from below. If your tub is in a sealed platform or mobile home, you may need to cut an access hole in the floor or wall, which is why a plumber is often the better choice in these situations.

What is the difference between plumber's putty and silicone caulk?

Plumber's putty stays soft and pliable, making it easy to remove if you need to service the drain later. Silicone caulk hardens and lasts longer, but it takes 24 hours to cure and is difficult to remove. For a drain you might need to access again, putty is the better choice.

How long does a new drain last?

A quality drain assembly typically lasts 15 to 30 years depending on water quality and how often the tub is used. If your water is hard or acidic, the metal parts may corrode faster. The putty or caulk seal usually needs refreshing every 5 to 10 years if you notice slow draining or leaks.

Do I need to turn off the water before I start?

It is not strictly necessary because you are not cutting into supply lines, but it is a good safety habit. At minimum, know where your main shutoff is in case something goes wrong. If you accidentally damage a pipe underneath, you will want to stop the water flow immediately.

What if water is still pooling under the tub after I finish?

The most common cause is incomplete cleaning of old putty before you installed the new drain. Remove the drain, scrape the opening completely clean with a putty knife, and reinstall with fresh putty. If the leak is from the trap connection, try tightening the slip nut slightly — but stop if you feel resistance, as over-tightening can crack plastic.