I get some of the strangest looks from employees at Home Depot when I tell them what I need parts for. The drain here is made of 1 inch pipe and t fittings. There is a 1 inch elbow at the end (not shown.) The elbow in the picture has a 1/2 inch threaded opening that is supposed to be for a relief valve but it makes a great drain for this part of the system. Due to the slow water flow from the drip system there is no danger of overflow from a smaller pipe.