I want to add a PVC standpipe for the washing machine and have the 2" PVC trap drain into an existing 2" copper DWV pipe. Would like to tap into the copper DWV pipe by cutting out a segment and putting in a PVC sanitary tee. I was hoping to use a shielded coupling to connect the top and bottom side of the tee to the copper piping with a PVC spacer, but code provides the following:

"705.18 Joints between different materials. Joints between different piping materials shall be made with a mechanical joint of the compression or mechanical-sealing type . . . or as required by sections 705.18.1 through 05.18.7. . ."

"705.18.4 Plastic pipe or tubing to other piping material. Joints between different types of plastic type or between plastic pipe and other piping material shall be made with an approved adapter fitting. Joints between plastic pipe and cast iron hub pipe shall be made by a caulked joint or a mechanical compression joint."

Question: Does this mean that I cannot use a mechanical-sealing type coupling to go from copper to PVC, or is 705.18.4 just providing an alternative to 705.18? Was hoping I could avoid using copper fittings, since they are expensive and I probably would need to buy pipe and don't want to spend $100 for 10 ft, when I only need a couple feet.

Thoughts would be appreciated. Thanks!