I have a house built in 1915. The drain pipes leading into the basement from outside are thick lead. At the elbow(on top) on 2 of these pipes is a small hole which seems to have a cork or wood stopper of some kind..we accidentally found one on the floor while looking for the reason water was gushing into the basement every rainstorm. Evidentally the wood stopper just shot out like a wine cork! Anyone know the purpose of the small hole on the top of these elbows?