Can I Use Muriatic Acid to Unclog a Drain?

Muriatic acid is an industrial strength solution of hydrogen chloride gas dissolved in water. This chemical is also known as hydrochloric acid. While this acid has many household uses, clearing out clogged pipes is not recommended.

Popular uses for Muriatic Acid

Muriatic acid has a high degree of reactivity with lime, calcium and other elements that have a low Ph level, or a high base measurement. The chemical composition of muriatic acid makes it highly reactive, and highly corrosive. For these reasons, muriatic acid works well in some applications, such as cleaning brick of residual mortar after installation, etching concrete prior to the coating application, cleaning concrete and cleaning lime deposits from plumbing equipment, including tankless water heaters and convection radiators.

Corrosive Nature of Muriatic Acid

Muriatic acid is highly corrosive, which means when it comes in contact with specific materials, a chemical reaction occurs at high rates of speed. The reaction can be controlled when occurring in the open, but it can happen so quickly as to be deemed out of control when in a confined space, or in an environment in which the reaction cannot be moderated. For example, when used to etch concrete, the amount of water mixed with the muriatic acid can slow any reaction time. This reaction gives off hydrogen and chlorine gases. In an open environment, this reaction is of minimal risk to those nearby. However, if full-strength muriatic acid splashed onto unprotected skin, it can burn instantly. The actual chemical process called "corrosion" involves the reaction of the acid with another compound which results in the production and release of gases, hydrogen or chlorine, and the creation of a residual product, such as iron oxide or rust in the case of contact with steel.

In Consideration of Clearing Pipes.

Because of the intense nature of the corrosive chemical reaction, clearing pipes probably is not the best use for muriatic acid. Muriatic acid is not likely to react with PVC pipe. Nor does it react with copper, stainless steel or porcelain, the materials used for water-supply lines, sinks and fixtures. However, the materials in the pipes, which cannot be seen or known, can be problematic. If a homeowner's water supply has high levels of lime built up in drain lines, contact with muriatic acid could cause an explosive reaction. The result could be a splash of acid back out of the drain, showering a kitchen or bathroom with the caustic solution. Additionally, while most drain lines are plastic, copper or brass, older homes may have cast-iron drains in the floor, or out to the public waste systems. Muriatic acid does not react explosively with iron, but it will cause a slow corrosive reaction, which could cause leaks or failure in cast-iron drain systems.


In light of the presence of unexpected items in a drain, and the uncontrollable nature of the corrosive reaction which muriatic acid can create, it is not recommended to be used as a drain cleaner.