I am looking for the right size bulkhead to slip fit over a 1" schedule 40 pvc pipe. BRS "As we’ve explained, a 1-inch bulkhead accepts 1-inch PVC pipe and fittings. " I buy a 1" bulkhead and vendor says fits 1" pvc and doesn't fit. 1" pvc OD is 1.315" and every 1" bulkhead I find lists 1.2" for hole size. What am I missing here?