If the lowest drain in your basement (or other shower drain or toilet) is lower than this temporarily raised water level, you will find your basement drain backing up. In some cases the pressure created by the raised water level is so great that water raw sewage will be spewing several feet into the room from basement drains.
Flush the toilet and the water backs up into the bathtub or shower drains. Run the sink closest to the toilet for a minute and the toilet bubbles or the water level in the toilet rises. Use your washing machine and the toilet overflows or water backs up into the tub or shower.
You run to the bathroom and see a terrifying sight: dirty water rising up from your shower drain, threatening to overflow. As a homeowner, one of the scariest plumbing issues you can experience is having dirty water come up from your shower drain — especially if it reeks of raw sewage and is about to overflow the bathtub.
When water is backing up out of a floor drain, the causes are many. It typically means the house drain under your basement floor is full of water. That can mean a rainstorm has surcharged the drain system, or even the public sewer system. If there hasn't been a recent heavy rain, the there is probably a main line clog.
There's one trunk (main sewer line) that runs water waste out of the home. There are multiple small branches (secondary lines) that feed into that main line. If the clog is in in a secondary sewer line, then only a few drains will back up. In your case, the water from the toilet is backing up into the shower.
Today we had a really big storm and after raining all day the rain just came down in buckets. At that point water started to come out of the floor drain in my basement. I lifted the cover to the