Go to the hardware store and buy either a "water closet" or "closet" auger (a type of plumbing snake) and/or a "force ball" plunger. Your local hardware store should carry these, if not go online to find one. Both of these items are mechanical (so to speak) and do not employ the use of chemicals. The force ball plunger is the one that can capture more air to force down the drain. The plungers that are really flat, are useless, except for muting a trumpet! Also, you might have roots in your sewer line. I have lived in several old houses with this problem. Eventually the sewage backs up into the tub then overflows all over the floor. Not pleasant! If this is happening to you, call a plumber with a mechanical auger, it will cut the roots out and remove them. There is a chemical product called "Root Be Gone" at the hardware store, but I'm sure it isn't environmentally friendly, as it kills the roots inside the sewer-line. Until the sewer-line is replaced, you will need to do this once a year. Happy unclogging!