Busting concrete slab

Old journeyman showed me to use sledge hammer. Forgot weight . Said in basement floor tap the floor find "hollow" sound and proceed to bust it there . I now am 68-have a rental- with a slab which I think could be thicker than the 3-4" basements floors I remember. Had ducts cleaned. Guy was good. Some how noticed cold air return duct at bottom entrance to furnace filling with water when adjacent laundry tray drain ran. S trap 2" galv riser from floor drains L.T. I must repair. I thought of a liner. I thought of running a cable to make sure its open. I will bust the floor the 2 x2 area my duct cleaning guy recommended. He claims he has seen and fixed many of these old rusted pipes under floor. Just wondering any ideas what to rent to break this floor. How many amps max and if I should just hire it out to some handyman on craigs. Motown

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