I don't want Poop in my house!!

There is a thread about how long the water will flow out of the faucets after SHTF. Someone said something about only a matter of time when the electricity stops that we may start seeing the sewage back-up thru the shower, toilet etc..How does one stop this? What can you put over the shower drain or toilet. I don't want poop in my house. That is one stinky mess I dont want to clean up. Is there anything I can prepare right now to put over the drain? Im thinking maybe a 5 gallon bucket filled with cement to sit over the drain. But what about the toilet? Kitchen drains? Help