Customer called in with a leak from the upstairs through the ceiling into the downstairs. Arrived on site and inspected the issue. There is visible water damage on the basement ceiling directly below the upstairs bathtub. Provided pricing to attempt to locate the leak. The customer accepted the pricing. Laid down heavy plastic sheeting to protect the carpets in the basement. Made a small hole in the basement ceiling in the area with the water damage. Used a small camera to inspect the drain piping under the bathtub. Began running water into the bathroom lavatory and tub. There are no signs of a leak. Began splashing water onto the tub overflow, immediately water started dripping into the wall and onto the basement ceiling. The overflow cover is very loose because the screw that holds the cover on is not tightened. There is also no sealant around the overflow cover. Once the overflow cover had been removed we noticed the overflow gasket was not making contact with the outer t