Irrigation mainline crossing sewer line
I'm in the process of installing a sprinkler system. In digging the trench for the mainline, I discovered that I need to cross my house's main sewer line. Unfortunately, the sewer line is only 18" deep at the top.
Even though a permit isn't required here for sprinklers, I'm assuming that the mainline has to, or at least should, follow the same code limitations as the building supply lines. The California plumbing code (609.2) requires that all water pipes crossing sewer pipes made of clay, or materials not approved for indoor use, have a separation of at least 12". Additionally, the pipes must be buried at least 12" under ground.
Thus I believe that I need to replace a 3' section of the clay pipe with PVC/ABS, which will allow me to run the pipes with 6" separation. From my research it seems the best method for connecting clay to PVC/ABS is the flexible connectors, such as the ones may by Fernco.
Not having dealt with DWV lines before, I wanted to check to see if this sounded correct/logical before I had it added to my current plumbing permit. Also, I was curious if there were any better ideas for the situation, and/or for connecting clay to plastic pipe.
Finally, the sewer line runs parallel to the sidewalk leading up to the house. With the edge of the sidewalk pretty much on top of the center of the pipe. Are there any good methods to support the sidewalk while the area around the pipe is excavated?
Thanks in advance.