: Is it normal procedure to tie in graywater drain lines to the pipe that carries waste from the toilet to the septic tank?: Thank you very muchTerry, the short answer to your Question is yes. However, there are some systems that separate the greywater from the blackwater in order to more easily treat the greywater in a water recycling system. The treated greywater can then be used in an irrigation system or a separate plumbing system just for toilet flushing. Check out this web page http://www.alascanofmn.com