The worst way to fix a clogged drain is doing it yourself. Sure, a clogged drain is irritating, but seems like an easy fix. Just pour some drain cleaner down the hole and wait for the magic to happen, right? The problem is that magic will actually not happen, and some very bad things just might. Like:
You fill the air with toxic fumes
Do you remember every chemical that has gone down that clogged drain before you poured that caustic chemical in? Most retail drain cleaners are lye or bleach based. If you have rinsed an ammonia based cleanerdown the drain and then follow it with a drain cleaner that's bleach based, those two chemicals can combine and fill your house with toxic chloramine vapor, basically chlorine gas. If you are in unventilated area and inhale some of that, you could have serious medical emergency on your hands. Also, these chemicals are designed to dissolve organic matter to open clogged drains. You don't want that organic matter to be part of your body.
You burn a hole in your pipes
Pipes don't run in straight lines. They all have U shaped bends called drain traps that are designed to keep sewer gas from getting inside your house. If liquid drain cleaner gets into this trap, it will eventually chew a hole in your pipe and you will have a much bigger problem on your hand than a clogged drain. The acid will also eat away at enamel and other finishes in your sinks.
You might be wasting time (and money)
Not all clogs are located within a few feet of the clogged drain that you can see. If a clog is caused by a backup in another pipe down the line or some other cause, you will be pouring hazardous chemicals down a pipe that won't drain. The acid will just be chewing on your pipes and putting you and your family at risk for exposure to toxic fumes.
So what can you do instead? Nobody wants to call a plumber for a problem that could be an easy fix. If you have a clogged drain, simply try pouring boiling water mixed with dish soap down the drain first. Hot water will dissolve fat and grease, and the detergent will help carry it away. The more standing water you have at the top of the clog, the less effective this fix will be. The hot water has to come in direct contact with the clog to be able to dissolve it.
Still clogged? Bite the bullet and call a plumber. They can pull your pipes apart or use a snake device to deal with the clog permanently instead of you opening it up just enough to drain water for a week and then seeing the drain clog up again.