> I thought they contained lye, which is a base. <
That rings a bell, now that you mention it. So I did a little research. It turns out that some drain cleaners use sodium hydroxide (lye), and some use sulfuric acid instead.
One site mentioned that the sulfuric acid concentration in such cleaners can often be higher than 90%. (wow)
Seems like it would be hard on some drain pipes. I’m curious what was used. Orange juice is “ an acidic liquid “