Where tub drains fail
Under the tub, the drain fitting screws into a curved piece called the drain shoe, with a gasket and putty sealing it to the tub. The shoe connects to the overflow pipe and then to the trap. Any of those seals can let go as rubber ages, putty dries out or the tub shifts slightly over years of use.
Unlike an overflow leak, a drain leak shows up whenever water runs down the drain, including after a shower. It is often slow, so the first sign may be a faint ceiling stain, a soft spot in the floor beside the tub or a musty smell.
Checking for a drain leak
- Rule out the overflow.Run the two-fill test: if water appears below even when the tub is filled only partway, the overflow is not the only suspect.
- Run a shower only.Run the shower with the drain open for several minutes and check below. A leak now points to the drain or the walls and grout.
- Plug and release.Fill a few inches with the drain plugged, then pull the plug. A leak right as the water rushes out points to the drain fitting or shoe.
- Look at the access panel.If there is a panel behind the tub, shine a light on the drain and trap while water drains.
Tub drain repair options
| Problem | Typical repair | Access needed |
|---|---|---|
| Dried putty or gasket at the drain flange | Remove the drain fitting, reseal and reinstall | Usually from inside the tub |
| Cracked or corroded drain shoe | Replace the drain shoe and often the overflow with it | Access panel, wall or ceiling below |
| Loose slip joint at the trap | Tighten or replace the washer | Access panel or ceiling below |
| Cracked tub at the drain | Tub repair or replacement | Varies, often significant |
What drives the cost
- Whether the fix can be done from inside the tub
- Whether the drain shoe and overflow are metal, plastic or a mix
- Access: an existing panel, a new wall opening or the ceiling below
- Whether the drain is set in a slab and harder to reach
- Repairs to drywall, flooring or ceiling afterward
What to ask
- Which tests did you run, and which one brought the leak back?
- Can the drain be resealed from the tub, or does the shoe need replacing?
- If the overflow is the same age, should both be replaced together?
- What opening will you need, and who patches it?
Common questions
Can a slow tub drain cause a leak?
A slow drain itself doesn't leak, but water standing in the tub longer puts more time on a weak drain seal. Clearing the clog and checking the seal together makes sense.
Is a drain leak worse than an overflow leak?
It usually leaks more often, since every shower triggers it. Both cause damage over time.
Do I need a new tub?
Rarely. Most drain leaks are fixed with new seals or a new drain shoe. A cracked tub is the exception.
General information for Fullerton, not a quote or professional advice. In an emergency, call 911.