Customer called us out for a clogged kitchen sink. On arrival the p trap had already been disassembled and cleared by the customer. I put it back together and tested the sink and it backed up within 30 seconds. Customers garbage disposal was also very old and rusted together. I quoted the customer to run a k400 down the kitchen sink line and remove and replace the garbage disposal with a new 1/2 HP Insinkerator. Customer agreed. I also recommended getting Endure drain line maintainer, the customer did not want to get it today. I removed the garbage disposal and ran the k 400 down the kitchen sink line 3 times. I then installed the new disposal and tested for any back ups by running the water for 20 minutes while I cleaned everything up. There were no signs of back ups.