Reddit reviews EZ-Flo 43507 3" Sewer Relief Valve

You didn't name your source, and generally simply googling things doesn't always give you an authoritative answer. Whereas talking directly with an authority who can give an authoritative answer is generally better, especially when it involves very large financial transactions.

So if you actually are responsible for the sewer past your property line, I wouldn't buy that house. The line has a 7+ foot dip in the line. Anything getting put down the sewer besides shit and toilet paper is going to eventually clog up that line. Even using the garbage disposal could be a bad idea, depending what is going down, could contribute. Like rice tends to get really gummy after going through disposals. Or even if you have a kid, who might flush a toy down the toilet. Not something you want sitting at the bottom of a dip in a sewer line. But it does have that cleanout 60' out. You could put a sewer relief at the 60' cleanout, so when the sewer does backup, it'll just come out of that cleanout instead of making its way back to the house.

The roots aren't that bad and can be controlled without the use of a sewer machine.

The dip in the line is the most concerning just because of how long it is.