The trickiest part of replacing tub drain hardware isn’t the new install — it’s getting the corroded old strainer out without cracking the tub. A 30-year-old brass drain bonded to a fiberglass surround has thwarted more weekend projects than any other plumbing task. With the right tool and a few prep steps, the swap takes 45 minutes and runs under $40 in parts.
- When to Replace a Tub Drain
- Tools You'll Need
- Step 1: Identify Your Drain Type
- Step 2: Remove the Old Drain
- Alternative: Stripped Crossbar Removal
- Step 3: Clean the Drain Opening
- Step 4: Install the New Drain
- Step 5: Test for Leaks
- Common Issues and Fixes
- Drain Won't Thread All the Way
- New Drain Leaks From Top
- Drain Leaks Below Tub
- Stopper Doesn't Hold Water
- Cost Range
- Pro Tips From the Field
- FAQ
When to Replace a Tub Drain
Common reasons homeowners pull a tub drain:
- Persistent leak below the drain assembly into the floor or ceiling below
- Corroded or chipped drain finish (chrome flaking, rust spots)
- Outdated style — switching from old brushed finish to modern matte black or polished nickel
- Stripped crossbars on the strainer that no longer accept a drain key
- Switching mechanism — toe-touch, lift-and-turn, or push-pull replacements
If the leak is at the overflow plate (the round plate higher up on the tub end), that’s a separate gasket repair, often easier than a full drain replacement.
Tools You’ll Need
- Drain key or “smart dumbbell” tool — Cobra 365 ($12 at Home Depot) or Superior Tool 03825 ($18)
- Channel-lock pliers
- Plumber’s putty (Oatey Stain-Free, $5/14 oz)
- Flat screwdriver
- Towel or soft cloth (protects tub finish)
- Penetrating oil (PB Blaster or Liquid Wrench) for stuck drains
- Heat gun or hair dryer (last-resort persuasion for stuck drains)
- New drain assembly — $20-$35 depending on style and finish
Step 1: Identify Your Drain Type
Before buying parts, look at how the drain operates.
- Toe-touch (toe-tap) — push down with foot to open and close
- Lift-and-turn — small knob on top of strainer rotates
- Push-pull — pull up to open, push down to close
- Trip lever — handle on overflow plate connects to internal stopper
- Pop-up — similar to bathroom sink mechanism
The thread size at the tub shoe (the elbow below the drain) is almost always 1.5-inch standard pipe, but always confirm before buying. Big-box stores stock universal kits like Danco TRIM by Design that fit most modern tubs.
Step 2: Remove the Old Drain
Insert the drain key into the strainer crossbars. Apply firm steady pressure counter-clockwise. If it spins freely without unthreading, the crossbars are stripped — skip to the alternative removal section below.
For stuck drains, soak the threads with penetrating oil for 30 minutes. Then wrap a damp cloth around the drain key handle, apply heat from a hair dryer for 60 seconds (heat expands the metal slightly, breaking the corrosion bond), and try again.
Never hammer the strainer or strike it with a chisel. The shock can crack acrylic or fiberglass tubs, which costs $1,000+ to repair.
Alternative: Stripped Crossbar Removal
If the crossbars are stripped, use a Pasco Tub Drain Extractor ($25). It’s a tapered tool with reverse-cutting teeth that bites into the inside of the drain when turned counter-clockwise. Set it in place, give it a few taps with a small mallet, and turn with channel locks.
For desperate cases, a Dremel with a metal cutting wheel can score two relief cuts down the drain wall. Then use a flat screwdriver to fold the metal inward and pull it out. Slow, careful work — protect surrounding surfaces with painter’s tape.
Step 3: Clean the Drain Opening
Once the old drain is out, scrape away all old plumber’s putty from the rim of the tub. A plastic putty knife works without scratching. Wipe the drain opening with paper towels and rubbing alcohol to remove any oil residue. The new putty needs a clean, dry surface to seal properly.
Inspect the drain shoe (the elbow below) for cracks or corrosion. If it shows damage, address that before installing the new drain — leaks at the shoe ruin floors and ceilings.
Step 4: Install the New Drain
- Roll a rope of plumber’s putty between your palms — about 8 inches long, 1/2 inch thick.
- Press it onto the underside flange of the new drain strainer.
- Lower the strainer into the drain opening, threading it into the shoe by hand first.
- Use the drain key to tighten clockwise until snug. Don’t over-torque — that cracks the porcelain or fiberglass.
- Wipe excess putty squeeze-out from inside and around the drain.
- If the kit includes an overflow plate, replace that too. Remove the trip lever screws, swap the plate and gasket, and reinstall.
Step 5: Test for Leaks
Run water in the tub for 5 minutes, watching the area below if accessible (basement ceiling, crawlspace, or access panel). Then fill the tub halfway and check again. Static water tests pressure on the drain seal that running water doesn’t.
If you see a drip, tighten the drain a quarter-turn and retest. Persistent leaks usually mean insufficient putty or a damaged shoe.
Common Issues and Fixes
Drain Won’t Thread All the Way
Cross-threading. Back it out, clean the threads, and start over slowly by hand.
New Drain Leaks From Top
Putty wasn’t continuous around the flange. Remove, reroll, and reinstall.
Drain Leaks Below Tub
Damaged or worn shoe gasket. May require accessing the shoe from below or replacing the entire drain shoe assembly.
Stopper Doesn’t Hold Water
For lift-and-turn types, adjust the stopper post height. For trip-lever types, adjust the linkage rod inside the overflow.
Cost Range
- Universal drain kit: $20-$35
- Premium finish (matte black, brushed nickel): $40-$70
- Drain key tool: $12-$25 (one-time investment)
- Plumber’s putty: $5
- Penetrating oil: $7
Total DIY: $45-$110 including tool. Hiring a plumber for the same job runs $150-$300, mostly labor.
Pro Tips From the Field
Skip silicone caulk in place of plumber’s putty. Silicone bonds permanently and turns any future replacement into a nightmare. Putty stays pliable for decades and removes cleanly.
Take a photo of the old drain before removal. If you encounter unfamiliar parts during reinstall, the photo helps confirm orientation.
If the tub is a one-piece fiberglass surround glued to studs, work cautiously — flexing the floor of the tub puts stress on the seams.
FAQ
Can I replace a tub drain without going under the tub?
Yes for most drum or compression-style drains. The strainer threads into a shoe that stays in place. Only certain solvent-welded plastic systems require shoe replacement from below.
How tight should I tighten a tub drain?
Snug, plus a quarter-turn — about the same torque as a stuck pickle jar. Over-tightening cracks the tub. Under-tightening leaks. The plumber’s putty does most of the sealing work.
Do I need plumber’s putty or silicone for replacing tub drain?
Plumber’s putty is standard and easier to remove later. Some manufacturers spec silicone for stone or solid-surface tubs — check the tub manufacturer’s documentation if unsure.
Why is my tub drain still leaking after replacement?
Either the shoe gasket below the tub is worn, or the new putty seal is incomplete. Check both. The shoe gasket may require accessing the underside of the tub through a basement ceiling or access panel.
