Chemical drain cleaners: label rules and the mixes to avoid

Drain cleaner safety comes down to three rules: follow the product label exactly, never mix a drain opener with bleach or any other cleaner, and do not pour chemicals into a sewer line that is completely blocked. Most drain openers are strong alkalis such as lye or strong acids, and both can cause serious burns.

The National Capital Poison Center says lye gives off toxic fumes and can cause skin burns and severe eye injuries, including blindness, if the liquid or fumes get close to the eyes (Poison Control). Acid drain and toilet cleaners are corrosive as well. The center's first rule for household cleaning products is simple: never mix them.

The mixes that make gas

The New Jersey Department of Health's hazard alert on mixing cleaners explains the chemistry. Bleach mixed with ammonia produces chloramine gas. Bleach mixed with acids, which include some drain openers, produces chlorine gas (NJ Department of Health). The alert describes a plumber who was hospitalized after pouring a sulfuric-acid drain product into a drain that already held bleach.

The Poison Center lists eye, nose and throat irritation, coughing and difficulty breathing among the symptoms of mixed-cleaner fumes (Poison Control). The same caution applies during sewage cleanup, when bleach is common; CDC cleanup guidance bars combining bleach with ammonia or with any second product (CDC). See sewage backup cleanup.

What one acid label says

A maker's label for a sulfuric-acid drain opener sold to plumbers shows how narrow the safe use is. It says not to use a plunger, warns that hot acid may erupt from the drain, tells the user not to stand over or look into the drain, and says not to use it where other drain cleaners are present. It also warns that old pipe may be porous, with defects sealed only by built-up organic matter, and that the acid can open those defects and cause leaks. That is a real concern in houses with original cast iron or clay.

The Poison Center records a case of a 2-year-old splashed in the face with lye drain cleaner when someone poured it into a sink full of water. Standing water in a sink or tub is exactly where a homeowner is tempted to pour a product.

When not to use chemicals at all

When several fixtures back up together, the clog sits in the shared pipe beyond them, and a chemical will sit in the pipe, or in the basement, without reaching it. A plumber who later opens that line meets the chemical too. See main sewer line clog and signs of a sewer line problem.

The NYS Department of Environmental Conservation puts mechanical options ahead of chemicals: a strainer over the drain, coffee grounds and hair in the trash, and a plunger or hand snake when water stops moving (NYS DEC). Root killers are a separate product class with their own federal labels; see copper sulfate root killers.

Key facts

• NJ DOH: bleach plus ammonia makes chloramine gas; bleach plus acids, including some drain openers, makes chlorine gas (NJ DOH).
• Poison Control says lye fumes or liquid can cause severe eye injury, including blindness (Poison Control).
• Mixed-cleaner fumes can cause coughing and difficulty breathing, per Poison Control (Poison Control).
• NYS DEC recommends strainers and a plunger or snake to clear drains (NYS DEC).
• The CDC says bleach should never be combined with ammonia or another cleaner (CDC).

Sources

• National Capital Poison Center — spring cleaning tips
• New Jersey Department of Health — Hazard Alert: Mixing Cleaners
• National Capital Poison Center — unknown fumes
• NYS DEC household hazardous waste guide
• CDC cleanup safety after a disaster