Step 3: Cutting the overflow hole
A 2-3/8 circle will be used for your overflow hole. Determine what side of the barrel you want your overflow hole to be on. Measure down from the top of the barrel approximately 4 inches. The bottom of the 2-3/8 circle should be slightly below this mark.
Again, using an appropriate saw, cut out the circle you just traced.
Note: The 2-3/8" hole is appropriate for the 2" PVC male adapter. It will be too big if you use 1-1/2" fittings.