Why the overflow leaks
The overflow is the opening behind the round cover plate near the top of the tub. Behind it, a pipe runs down to join the drain. A rubber gasket seals that pipe against the back of the tub, and when that gasket shrinks, cracks or shifts, water from a full bath runs down the outside of the pipe instead of inside it.
Because the overflow only gets wet when the water level is high, this leak hides. Showers never trigger it, and shallow baths may not either. The telltale is a stain on the ceiling or wall below that grows only after someone takes a deep bath.
The two-fill test
Do this when someone can watch the ceiling or wall below. Have towels ready.
- Fill below the overflow.Plug the tub and fill it to a few inches under the overflow opening. Wait at least 20 minutes and check below for drips.
- Drain and dry.If nothing showed, drain the tub and let the area below dry so a later leak is easy to spot.
- Fill above the overflow.Fill again until water is running into the overflow opening, then turn the water off and watch below.
- Read the result.A leak only on the high fill points to the overflow gasket. A leak on both fills points lower, to the drain or the tub itself.
How the repair is reached
From inside the tub
- Some overflow assemblies can be reseated or regasketed from the front
- Uses special gaskets designed for front installation
- No wall or ceiling opening
- Works only with certain assemblies and enough room
From behind or below
- Through an access panel or a small opening behind the tub
- Or through the ceiling below on a second floor
- Lets the plumber see and replace the whole overflow pipe
- Means a drywall patch afterward
What drives the cost
- Whether the gasket can be replaced from the front of the tub
- Whether there is an access panel behind the tub
- Whether the overflow and drain pipes are old and brittle enough to replace
- How much ceiling or wall drywall has to be opened and patched
- Whether water damage below needs drying or repair
What to ask
- Did you test below and above the overflow, and what did each show?
- Can this be done from the tub side, or do you need to open the ceiling?
- Will you replace the full overflow and drain assembly or just the gasket?
- Who patches the ceiling afterward?
Common questions
Is it safe to use the shower while the overflow leaks?
Usually yes, since a shower doesn't fill the tub high enough to reach the overflow. Avoid deep baths until it is fixed.
Will caulking around the overflow plate fix it?
No. The leak is at the gasket behind the tub wall, not at the cover plate, so caulk on the plate won't stop it.
Does a single-story house have this problem too?
Yes, but the water ends up in the wall, floor or slab instead of a ceiling, so it can go unnoticed longer. Look for swollen baseboard or damp flooring next to the tub.
General information for Fullerton, not a quote or professional advice. In an emergency, call 911.