My basement toilet and shower will not drain after it rains
If your basement has a back flow preventer when the water level is high the pressure in the line from a raised water level is probably the cause. I had this happen, built the bathroom in the summer, it worked great until several days of rain then no draining like you have. Whatever you do don't make the mistake I did and think the back flow valve was plugged , when I opened it up got all the brown trout from the line above. I ended up having to add a pump to the system if I remember correctly it was around 500$ for the tank&amp; pump a small one but we never had any problems after that.