Backwater Valve question

[Dante1]

hello everyone,
I’m adding a bathroom in the basement and had a question. I’m adding a shower, toilet and vanity. I managed to find the main drain line which is in line with the stack. I am wondering if I should install the back water valve then the “T-Y” to bathroom or should I install the “T-Y” and then the back water valve to the bathroom?

Thanks

 

[Sylvan]

Why would you want to use a "check" valve to impede flow ?

 

[Sponsor]

 

[Dante1]

Why would you want to use a "check" valve to impede flow ?

You install a backwater valve to prevent sewer back flow.

 

[Sylvan]

Then you KNOW it is after the house trap or LAST connection and ONLY if there really is a need for one and it better be accessible and a sign posted so some poor drain cleaner does not get their cable stuck