Muriatic acid is very effective for cleaning drains, although it should probably only be used after all else fails. The fact that it’s acid, more specifically a type of hydrochloric acid solution, means that it needs to be used with very great care. When you use muriatic acid for cleaning a drain, protect yourself thoroughly by wearing heavy gloves, safety goggles, and a face mask to prevent the acid from accidentally splashing into your eyes or onto your skin, to avoid touching your hands to your face, and use an appropriate respirator to avoid inhaling fumes.
How It Works
Muriatic acid is exceptionally strong and causes a chemical reaction with the items that are blocking the sink. The reaction creates heat, and that is what breaks up the blockage. It works fairly quickly, so expect a solution much more quickly than with other methods you might try.
It can’t be stated too strongly that muriatic acid is dangerous and needs to be used with safety equipment and according to the manufacturer’s instructions.
When to Use
As mentioned previously, start out by using gentler solutions to clean out your drains if they’re clogged. These will remove small clogs and also clean the drain. If that doesn’t work, move to progressively stronger methods to see if they will do the job. Only when all the others have failed and you’ve determined that the clog is a very bad one should you move to muriatic acid.
Prepare Yourself and the Area
You need to use muriatic acid in a well-ventilated room. Ensure that the windows are open, even if it’s cold outside, since the acid fumes can burn your throat if the room isn’t properly ventilated. Put on the gloves, mask, and safety goggles before opening up the acid. You should also wear long sleeves to protect your skin from any acid splashes.
If your drain has a metal grating, use a screwdriver to unscrew it and set it aside. Muratic acid can damage some metal, so it's best not to pour it through a grate.
Using the Acid
For household purposes, you should never use muriatic acid without diluting the solution with water. This substance is very corrosive and if applied directly down the drain, your pipes may end up seriously damaged. Also, note that muriatic acid should always be added to water—rather than the other way around—to avoid splashing and a potentially dangerous reaction.
Measure out one half cup of water into a glass measuring cup; don’t use plastic for this. Add your muriatic acid to the water carefully, pour the diluted solution into the clogged drain, and leave for about 10 minutes. During this time the acid will work on the clog, heating it up, and breaking it up as promised. After the 10 minutes have elapsed, turn on the cold faucet and let the water run down the drain. The muriatic acid should have cleared the clog by this time, and your drain will be clean.
If At First, You Don't Succeed
In the event that muriatic acid doesn’t work to unclog your drain, you can try repeating the procedure but only one more time. Once more, put the acid down the sink and wait for 10 minutes before flushing with cold water. A second application should shift virtually every clog in a drain, but if, however, it doesn’t, then you’ll need to have the drains rodded. You can either do this yourself or employ a professional. However, do not try using muriatic acid more than twice on a clog or you will risk damaging the pipes themselves.