There is a mystery leak in my basement near the drain hole and near an outside wall. The house is 3 stories and it takes forever for the bathroom sink and tub to drain which is on the 3rd floor. Recently had a major flood in the basement where all the flooring /drywall had to be removed. They had fans etc going for 4 days to dry everything up, but went down to the basment and there is water coming up from the floor near the drain hole. They said the flood was due to heavy rains and not being able to hold it. Want to get this fixed before they start fixing the damage. Not sure if there is a leak in the main drain, or how to check it. House is 50+ years old. Hopefully seeling it soon and moving back to the country. Basement has always had small leakage since we bought it 2 yrs ago. Didn't know any of this stuff before I bought it. Any help would be appreciated!