A.Master plumber Rex Cauldwell responds: Yes, the line will definitely clog up more often. In my experience, having a shallow pitch for 30 feet is asking for trouble — especially on a kitchen drain line, which is more prone to clogging anyway because of all the grease and food solids it has to carry. For one thing, the pipe is rarely set dead straight, but instead tends to wander slightly up and down, which speeds up the clogging process.

Before installing the disposal, I would either increase the slope of the pipe or increase its size to 3 inches. Either strategy has its difficulties. Increasing the slope of the pipe often requires cutting joists, which may not be possible. Increasing the pipe size will require cutting in a new tee on the main cast iron line — which is not an...

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