The short answer is that it’s best to avoid using these products. If you have a major clog, a chemical drain cleaner won’t be very effective. You’ll need to call in a plumber to take a look at the problem. A licensed plumber can use a snake or hydrojetting equipment to clear away the clog without dumping harmful chemicals into your system. Here’s a quick look at exactly why it’s best to avoid using a chemical drain cleaner whenever possible.