Because it corrodes metal, sulfuric acid can damage chrome, stainless steel and galvanized steel plumbing pipes. It's recommended for use only if you have plastic plumbing pipes, and even these can sustain heat damage if you introduce the drain cleaner too quickly or use too much of it.

Is sulfuric acid safe for drain pipes?

About Sulfuric Acid used as a Drain Cleaner

it is safe to use with plastic piping. Sulfuric acid is very simple to use and will unclog a drain within an hour, usually within seconds if it's not completely plugged up.

What happens when you pour sulfuric acid down the drain?

Even once a clog has been cleared, sulfuric acid drain cleaner could still cause problems. It has the potential to kill the necessary bacteria in a septic system and it can cause pipes to corrode. Sulfuric acid also can cause environmental problems, depending on the type of sewage system in an area where it is used.