Our washing machine drain backs up every 6 months or so. It is a 2" cast iron pipe and we can only get the smallest snake through. The large snake won't penetrate past 2' down the drain. Is this a 1/4 turn problem? Will I have to tear out the drywall and replace the cast iron pipe with pvc? Could an object be preventing me from getting the snake past the turn? Would jetting solve the problem? What would you recommend I do? Herman