When cutting out a section of cast iron building drain to insert an MJ wye, how much pipe should be removed?

When cutting out a section of cast iron building drain to insert a mechanical joint (MJ) wye, it is important to consider the length of pipe that needs to be removed to accommodate the fitting properly. The correct amount of pipe to be cut is typically 1/4 to 1/2 inch longer than the wye itself. This additional length accounts for the proper spacing needed for the MJ fittings, which includes the joint and any necessary movement or adjustments during installation.

By removing this specified amount, you ensure that there is adequate overlap for the joint, allowing for a secure and leak-free connection. Additionally, this length allows for the installation of any necessary sealing or gasket materials that might be used with the MJ wye.

Other choices suggest either too little or too much material removal, which could lead to installation challenges, such as insufficient joint strength if too little is cut, or excessive gaps if too much is cut. Thus, the option of removing 1/4 to 1/2 inch longer than the wye strikes the appropriate balance for a successful installation.