Design Master Plumbing automatically inserts a break when two pipes cross. The lower elevation pipe is the one that breaks. This setting determines the width of the break.
To set the width, select:
DM Plumbing 
Customization Options Edit Standards List
The Design Master Plumbing Options dialog will appear.
Set the value to the desired width. The number in the value field is the size of the break on a printed drawing. The example of 0.1 means that the break width will print at 1/10th of an inch.