Tub overflow leaks in St. Louis homes are easy to misread. Water shows up under the tub, on the ceiling below, or along the baseboard, and it is not always clear whether it came from the tub, the drain, or a supply line behind the wall. This guide walks through the overflow parts in order so you can narrow it down before you open the wall or call anyone.
What the overflow is
Most bathtubs have a small opening near the top of the tub wall, often covered by a decorative plate held on by a few screws. That opening is the overflow. Behind it, a short passage carries water down into the drain body below the tub, so water that rises above the normal fill line goes to the drain instead of onto the bathroom floor. The same passage also connects to the trip lever, the knob or lever you pull to open and close the stopper. Because one passage serves both jobs, a problem with the overflow can look like a drain problem, and the reverse is also true.
The gasket and linkage
Where the overflow passage meets the drain body, there is a gasket or sealing ring. Over the years it can harden, shrink, or slip out of position. The trip lever linkage also passes through this area, and a loose or bent linkage can change how the seal sits. Some tubs give you access to the overflow tube from the panel below the tub. Others only allow access from the front or back of the bath surround.
Signs it is the overflow
- Water collects behind or around the overflow plate when the tub is full.
- Drips appear under the tub mainly when the water is running or the tub is filling near the top.
- The leak stops when you drain the tub below the overflow opening.
- You see a stain or soft spot on the subfloor or basement ceiling directly under the tub.
If the leak keeps going when the tub is empty and the stopper is closed, look elsewhere first, such as the supply valves, the tub spout, or the wall behind the faucet.
A simple test you can run
- Dry the tub, the floor around it, and the area under the tub as well as you can. Place a paper towel or a flat piece of cardboard under the drain area so you can see fresh moisture.
- Close the stopper and fill the tub with water until it reaches just above the overflow opening.
- Watch the overflow plate and the area beneath the tub for several minutes. Check the towel again after the water has been sitting.
- Drain the tub and check whether any water is still trickling from the overflow or the drain body.
Take notes on which step produced the water. If it appears only when the tub is full to the overflow line, the gasket or overflow passage is the likely source. If it appears during draining, the drain body or its connection is more likely.
What you can check without opening the wall
Remove the overflow plate if it comes off with a screwdriver. Look inside the opening for cracked caulk, a loose tube, or residue that shows where water has been running. Check the trip lever for play. If the lever moves freely but the stopper does not seal, the problem may be the linkage rather than the overflow, and that is a separate repair.
When to open the access panel
If the test points to the overflow passage, you will need access from below. In many St. Louis basements, the area under a tub is reachable through a panel in the wall of a lower room or through a crawl space hatch. Before you disconnect anything, shut off the water supply to the bathroom and place a bucket and towels below the work area. Older tubs can hold rust and sediment in the drain body, so expect some debris when you loosen the overflow tube.
Where to stop and get help
If you find a cracked drain body, a damaged tub floor, or water on the subfloor that has been there a long time, stop and have a licensed plumber look at it. Keep your test notes and photos. They will help whoever comes out understand what you already ruled out, and they will save time on the call.