Customer stated shower drain had backed up and black debris came out of drain. This unit is located on the second floor. All other fixtures in this unit are draining properly. Large amount of buildup backed up into shower. Ran fixtures verifying proper drainage. All fixtures in unit below are draining properly. Ran shower for 10 minutes verifying proper drainage. Provided estimate to attempt to clear shower drain line. Also provided estimate to inspect drain with camera. Customer will proceed with drain cleaning if unit backs up again. Thank you for choosing CPI plumbing and Heating.