Since the post on infrastructure failure, I have received several inquiries for additional information on how to plug your sewer line. The method that I mentioned using Ready Crete works well if your house is on a slab or if access to your sewer lines is a problem. You need to find the clean out which is normally located on the outside of your home. Open the plastic screw lid with a wrench or large set of channel locks. Mix the Ready Crete per directions and pour into the clean out. Use a stick to tamp it down so that the line is completely blocked. This should be done before the sewage starts to backup.
The down side to this method is that when the emergency is over you will have to dig up your sewer line and replace this section. If the sewer backup has already started you have a real problem. Hopefully you can shove something in to make a temporary blockage while the Ready Crete sets.
Another method is to use an end cap these require that you have access to your sewer line and can cut it. Then you merely glue the cap in place using ABS glue. If you have good access this is the best method. If you are on a raised foundation (a crawl space under the house) this will probably be your best method.
A third method is to get a plumbers test plug. They can be found at most plumbing suppliers. They come in two types one is used similar to an end cap and requires that the line be cut. It is then placed in the line and tightened per the instructions with it. The other type is pneumatic. You shove it into the line and pump it up with air.
Most household sewer lines are 4 inch plastic, although some older homes may still be cast iron. In any emergency the earlier you can plug your line the better. Once the sewage starts to backup, your problems increase. Because of the differences in types of construction and materials, I cannot tell you exactly what you may have to do at your home. The blockage needs to be in the main sewer line entering your home so that one block will work for the entire system. Remember this will not be needed if you are on a septic tank or live on the up hill side of your sewer line.