Does baking soda and vinegar really unclog a drain?

When you combine the two, the mixture fizzes and produces carbon dioxide and water. Liquid-Plumr, a drain-cleaner manufacturer that publishes a how-to for this method, describes it as a reaction that creates carbon dioxide and water that "bubbles through the clog, breaking it up." That bubbling can nudge a thin layer of soap scum or grease near the opening.

That is about the limit. Even the manufacturer says so. Liquid-Plumr writes that with time baking soda and vinegar "may work as a natural drain cleaner on weaker drain clogs," and that "for tough drain clogs that need to be dissolved right away" you may want a stronger product. In other words, a small, soft, close-to-the-surface clog is fair game. A clump of hair, a wad of grease down the line, or a foreign object is not.

Two things explain why it disappoints. The reaction is quick, so the fizz is over in minutes. And a drain is an open pipe, so gas simply escapes upward and out. There is no sealed space in which pressure can build and push a clog through. This is my own reasoning from how the parts fit together, not a claim from a source, but it matches what most people see in practice: fizzing, then no change.

Which clogs might it help, and which will it not? Match the mixture to the clog before you pour anything:

• A light film of soap scum in a bathroom sink. Fair candidate. The clog is soft, thin and close to the opening.
• A thin coat of grease on a kitchen drain. Possible help, especially with hot water first and last. Grease that has hardened farther down the line is beyond it.
• A clump of hair. Unlikely. Hair is a physical mat, and fizzing does not dissolve it. Pull it out, or hook it with a wire or strip.
• A foreign object, like a toy, a cap or a bit of packaging. No. Only removal works.
• Roots or a collapsed pipe. No, and the symptoms are different: several drains slow, repeated backups, a smell.
• Mineral scale. Not something a single treatment will fix.

The pattern is simple. The more solid, the deeper, or the more widespread the problem, the less this helps. It is a maintenance trick for early, mild buildup and a very weak fix for a serious clog. Most of the time, the homeowner who is disappointed by this method had a clog it was never going to reach.

Before you start, clear what you can by hand. Lift out any hair or debris at the opening, take off the stopper or strainer, and remove standing water with a cup if the basin is full. The mixture works only where it can reach the buildup, and a drain full of water dilutes it. Then follow a tested recipe.

If you want to try it, use a version with a source behind it. AAA's home-advice list of chemical-free strategies gives a mixture of one-third cup each of baking soda and vinegar. Its key step is the water: "pour hot water down the drain first, then add the mix, followed by more hot water." Liquid-Plumr's version is four steps: boiling water, then baking soda and a vinegar solution, cover the drain for five to ten minutes, then boiling water again.

A few practical notes:

• Use hot tap water on plastic pipe. AAA notes that boiling water can melt debris and create a second clog farther down, or cause pipes to expand and leak. Hot tap water is enough.
• Cover the drain while it works, so the fizz pushes down the pipe and not into the sink.
• Give it ten or fifteen minutes, then flush with hot water.
• Try it once. If the drain is still slow, more mixture will not help.

AAA also lists baking soda with salt, but it adds a caution: "salt is not good for your pipes," so use it sparingly. There is no reason to make this a weekly habit.

Fizz and time do not remove hair, food or objects. Something has to grab, push or pull them out. That is why every method on the list below moves the clog physically.

A tool that removes the clog beats a fizz that hopes to loosen it. For a real clog, go mechanical:

1. 1A plunger. InSinkErator's own clog guide for a disposal sink pairs baking soda in warm water with a plunger: fill the sink halfway with warm water, add baking soda mixed with water, place the plunger over the opening and "press down slowly and gently. Then, pull the plunger upwards quickly." The plunger does the work.
2. 2Cleaning the P-trap. AAA lists it as a standard step. Our slow-draining sink page walks through it.
3. 3A hooked wire or a drain strip for hair. Delta suggests a straightened coat hanger for shower drains. Our drain zip tool and unclog a shower drain pages cover both.
4. 4A drain snake. For clogs beyond the trap.

Do not stack products. If you already poured a commercial drain cleaner into the drain, do not add vinegar or anything else to it. MedlinePlus warns that drain cleaners contain "very dangerous chemicals," and in its first-aid steps for skin or eye contact it says to flush with water and not to use vinegar or lemon juice to neutralize the chemical. Keeping the two apart is simply safer. If you have used a chemical cleaner, our is Drano bad for pipes page explains what to do next.

Also keep vinegar and baking soda away from the disposal blades as a cleaning routine. A disposal is best cleaned as InSinkErator describes, with the power off and a scouring pad on the underside of the baffle, since you should never put your hand in the unit.

For a gentler maintenance product, see do enzyme drain cleaners work.

For a kitchen drain, the better fix is prevention. Phoenix Water Services calls grease the most frequent cause of sewer problems and says to let cooking grease or oil cool, then dispose of it with the garbage, not down the drain. No fizzing treatment undoes a habit of pouring fat down the sink.

If the drain is still slow after one try, stop. Water that will not move in a sink, or a clog that returns within days, means buildup deeper in the line. Read why the same drain keeps clogging. And if several fixtures are slow, the problem is not one drain. See main line vs branch clog.

HQ Plumbing & Air gives free estimates and upfront pricing when it is time for a real fix, and is licensed, insured and available 24/7.

For methods that do work, from the P-trap to a hand snake, see how to clean the pipes in your house.