Performed leak detection on customers master bathtub and found leak to be cause of the overlfow. Replaced overflow gasket and re tested and no longer saw any further leaks. As a result of the leak customer has water damage to surrounding walls, subfloor and ceiling/walls located below bathtub. Due to the bathtub being on a mortar bed and having particle board support located under the tub that’s damaged/compromised due to the water I strongly recommend removal of bathtub insert and surrounding damaged drywall in order to prevent further damage and mold growth. Once bathtub and drywall is removed we can then properly treat remaining structure with antimicrobial.