Cracks in basement cement that seem to leak more when water is running?
More leakage when you run the water points firmly to leaking from sewer line. A leaking water line would, if anything leak less when the water was run (or more likely just not change) since it has water under pressure in it all times.
A sewer line does not have water in it until you run the water, so if the leak leaks more when the water is running, it's from a sewer line. Crude home test method is to toss some food coloring (or unsweetened drink mix, which can be a handy source of strong color) into the toilet and flush, and see if the leak color changes to match (it will generally be more dilute, so use a strong color mix.)