11+ Shower Backing Up When Toilet Is Flushed Images. A shower drain backup isn't as common as a toilet or sink backups. There are just some things that should be kept separate—like your toilet and your shower, for instance.
Using a cup hold the cup upside down over the turn the water supply back on and let the tank refill.
Back them up with references or personal experience. 'toilet doesn't seem to want to flush properly and when it does there seems an airlock in the system somewhere which is coming up through the plug hole if it was an installation issue, then surely you'd of noticed after day 1. This is not an uusual as when the toilet is flushed more cold water is drawn usually from the cold water pipe that suplies the shower with cold water so generaly the water under the shower gets hotter. A clogged toilet on its own is bad, but when your toilet is backing up into your shower, things go from bad to worse.