First bit of advise. we think is important! If you have a drainage backup, avoid chemical drain cleaner at all cost!!! Many of these products are acids or caustics that react to the materials your plumbing is made of as well as the goop in the drain.
First these chemical generally will puddle in the bottom of the piping which will attack only the bottom on the blockage at best. If it corrodes its way thu it is generally on the bottom where it can eat away at the pipe and it produces only a small hole thru the blockage at the bottom of the pipe so the water drains away, but the biggest part of the blockage is still there. By the time most homeowners notice a backup, the original blockage is way down the line and enough stuff has flowed into the drain to fill it all the way back to the source. Thats a long way for the drain cleaner to trickle down to the blockage.
The second danger is the drain is now full of a corrosive soup that attacks the plumbers cable as well as your pipes. This can damage these cables as well as expose the plumber to potential corrosive burns.
Today there are products that clean and maintain open pipes with friendly bacteria that consumes the organic matter that enters your drains.
IDEA - When leaving home for more than a fews days we recommend shutting off the water to your home and preventing any surprising water leaks while gone. Water damage is actually the biggest source of homeowner insurance claims!
Run ice thru your disposer once in awhile to clean the chamber and blades.