What are bad dewatering problems

What could be causing drainage problems in our new bathroom?

If the problem isn't in your new drains, check the drain to the sewer.

When I lived in Mississippi, I suddenly had problems with water all over my house. When the washing machine was empty, water got into the tub. When we flushed the toilet, it was secured. I told my new neighbor about it and she said her toilet was secured, her tub filled with water at odd times. Within a few hours we realized that not only were each of us having problems, but that we were having problems together! When she was washing, my tub pulled back. When I flushed my toilet, hers would retreat. We knew it had to be the sewer, so we called the city to come out. Over 3 days and nights the city made us flush colored toilet paper and look down the manhole to see if our color got past. Our colors didn't come by so they found there was a plug in the Y where their drains and my drains met before going into the sewer. Fortunately, the plug was on the city side of the Y, so the city had to pay for the repairs. A tree root had found a crack in her side of the pipe and over time it had formed a ball of roots that clogged the pipes so that she and I drained each other. We became lifelong friends so it wasn't all bad. :-D I wish you all the best ...