It’s a set of threes. There are three rules you need to know about drain pipe. First, drain pipes need to slope downwards. Sloping up doesn’t do anything useful. Sloping downward does. In fact, some pipe needs to slope downward only slightly (like no more than 1/4 inch down for each foot of distance). This is common in plumbing pipe to make sure that solids, like cell phones and jewelry, are able to keep up with the liquids, like flat beer. Second, drains need to go somewhere eventually. Plumbi
