I drilled a hole in the cap and fit a nylon elbow into it from above. It's 1/2" barb (hose end) to 1/2" male NPT (end that goes through the cap). That threads into a PVC fitting that is 1/2" female NPT on top, and a meant-to-be-glued socket on the bottom that fits the OD of 1/2" PVC pipe. No need to glue as it's a tight friction fit.

I drilled a hole in the cap and fit a nylon elbow into it from above. It's 1/2" barb (hose end) to 1/2" male NPT (end that goes through the cap). That threads into a PVC fitting that is 1/2" female NPT on top, and a meant-to-be-glued socket on the bottom that fits the OD of 1/2" PVC pipe. No need to glue as it's a tight friction fit.