I discovered my mainline from the house to my septic tank is broken. I looks like the iron pipe was connected with about 2 feet of tar paper pipe, which then connected with blue plastic. The blue plastic line runs the rest of the distance (about 14' to the tank). The break is in the old tar pipe portion between the iron and plastic. Can I use a piece of white pvc to replace the gap between the blue and iron? Is white pvc the same as the blue?

I'm guessing a full replacement is the "right" thing to do, but I have extra white PVC layign around from an old gutter drain project and thought it could save me a trip to the plunbing supply (if it's just the same).