If it's deep, then make sure it's not tree roots. We had that situation and used draino a lot for a few weeks until we finally got the rooter guy out and found roots in the pipe. Within a month the big old magnolia tree died, probably from
the draino. They can usually handle roots being cut better than a nasty drain cleaning chemical. Of course, after it died no more drain issues!
Over the long haul paying a rooter is cheaper than using acid. I've seen cast iron that's been eaten by acid. It almost looks like the erosion from a tiny river that ran along the bottom of the pipe. I just replaced a cast iron drain & bath tub with damage caused by an acid drain cleaner. The renters denied using it, but the smell from recent use the & discoloration of the brass W&O & galvanized piping said otherwise. At this point the owner is talking about suing the renters for the cost of the repairs.
We hire out the rooter work, & for us the big name guys don't seem to work out as well as some of the smaller local guys. If you have a recurring problem, some of them have equipment where they can video the drain line to pinpoint the problem. The equipment also has a receiver that can be used in the yard to locate the pipe's path & depth. It shows you where to dig to replace a section where roots are an ongoing problem.
For my own house with 70 year old drain lines, I pay a rooter even though I'd do my own labor for free if the pipes were destroyed by acid.
What's clogging? Is it a single location that has a problem, or is it the whole house clogging at once?
He had a problem with clogged and slow drain. When the router rooter guy sent a 100' snake down the pipe and nothing. Then he said I gotta open the wall bang it was free and clear. He gave us this pipe treatment that is supposed to make the pipe walls super slick to things can't or don't clog that easy.