What can I use to stop the back flow of water from the toilet and washer In to the shower? The washer has a trap and when the washer drains and the toilet is used at the same time, water flows back into shower drain located in the basement.

Hi Tcepeda

Most likely, there is nothing to "use" here as your drain line is probably partially blocked up and needs to be snaked to correct the problem.

You can rent a snake or call a local plumber... ;)

Mark

You have a blockage downstream from the shower. Is the toilet in the basement with the shower? Is there a cleanout located on any other put the vertical stacks in the basement? Let me know, back to you, Tom

You have a blockage downstream from the shower. Is the toilet in the basement with the shower? Is there a cleanout located on any other put the vertical stacks in the basement? Let me know, back to you, Tom

Yes the toilet is the same room with the shower. And also I noticed a bad odor from the drains right before they back up

Hi tcepeda, I'm curious, are you on city sewer or a septic?

Hi tcepeda, I'm curious, are you on city sewer or a septic?

City sewer line

Thanks tcepeda, let us know how you do and good luck

The solution here would be you pull the toilet and snake the main drain. Good luck, Tom