Sources of Bathtub Overflow
One of the main causes of bathtub overflow can be found in the overflow drain. As time goes on, the gasket inside the drain can become brittle and cracked. This causes any water to reach the overflow and cause a massive leak.
Once the water reaches the wall cavity connected to the tub, this can cause the leak to go everywhere except through the drain where it’s supposed to. Checking the connection between the bathtub and overflow drain is of utmost importance, especially if you think that the seal or the gasket has been compromised.
Other causes can be as simple as the overflow plate being unsecured, allowing water to enter the overflow and not allowing the tub to drain properly. It’s also possible that the seal around the shower parts has minor cracks that might need re-caulking to close off any potential leaks.