Q: In 2013, we had our second level master shower remodeled. Since then about every two to three months a substantial amount of water pours through the fan/light vent in the first-story bathroom, which is directly below the master shower.
The plumber has come out once and could not locate the problem. The contractor is also unable to locate the leak. The leak has no association with the shower, flushing the toilet or using the vanity sink. Any suggestions would greatly be appreciated.
A: I have found situations similar to yours, and here are possible reasons a shower could leak.
1. If you have a fiberglass pan (bottom of the shower) it could be that the mortar underneath the pan was thrown in rather than spread out when the pan was installed, forming a cavity in the mortar that holds water until it overflows and leaks.
2. When the shower is on and there is no one in the shower, and therefore no weight on the drain, the shower does not leak. When someone is in the shower, the weight can push down on the floor and/or the drain and that may cause the shower to leak.
For instance, a small child may not have any effect on the drain, whereas an adult’s weight could cause the drain to leak.
3. Showers with glass walls can sometimes leak at the seams if the shower spray is hot. Hot water can cause the seams to expand when the water is splashed or directed at certain angles.
4. Another source of drips or leaks could be the vent fan in the first-floor bathroom. The fan is necessary to remove moisture from the bathroom.
If the fan is not properly ventilated to the exterior or if the vent pipe for the fan is exposed to cold air, condensation can form inside the vent pipe when the fan is used. Usually we see a water stain around the fan housing, but it can form a drip leak inside the fan.