/diy/ - Do It Yourself

Problem:

Washing machine and sink drain into the same pipe. (brown arrow in pic related). Water starts backing up into sink and washing machine drain pipe.

Snake drain to what I think in stack. Plenty of snake unrolled until hit barrier. snake won't penetrate. assume clog is where red arrow indicates.

Pour drain opener into sink and washing machine drain pipe and let it sit for hours. nothing happens.

Note: The run between the sick and washing machine is long and kind of up-slope to the stack/main drain (it was like that when I bought the house) so a gallon of drain cleaner may not get to the stack/main drain).

Go up to roof and pour half bottle of drain cleaner down stack pipe.

Next morning sink has drained. water flows well but not quickly. assume clog is open but not gone.

Question:

Would it be smart to pour foaming drain cleaner down the stack to try to clear out what is remaining of the clog?