Actually, the waste pipe needs to be 21-22 inches above the finished floor surface to the center line of the pipe. This will allow you to connect to the tailpiece of the sink without using any extentions. The water lines need to be 24 inches above the finished floor and 4 inches each side of the center line of the sink. This will allow you to use standard 12 inch supplies. Make sure to vent the sink properly. The vent should run vertical above the tee for the trap arm to at least 6 inches above the top of the sink, then it can run horizontally over to the toilet vent and tie in. The toilet vent should tie into the venting system of the house, or you will get sewer gas buildup in your basement bathroom.