Here’s why: they can’t tell the difference between the clog and the pipe. When a chemical drain cleaner finishes eating away at a clog, it’s going to keep eating away at your pipes. Not a good idea. Instead, try these other, lower impact ways of maintaining clear and clean drains:
Pour a large pot of very hot (but not boiling) water down a household drain. Follow it up with some cool water to flush out the clogs you just melted away.
Alternatively, you can use baking soda and vinegar. All you have to do is pour half a cup of baking soda down your drain and chase it with half a cup of vinegar. Plug the sink and let it sit overnight. Flush the drains with hot water in the morning and they’ll work (and smell) like they’re brand new.