I confess baking soda and vinegar to unclog a drain is something I have never used nor, had the slightest interest in using. It seems that everywhere I turn this popular drain cleaning myth comes up whether it is at a customers house, on-line in a plumbing forum or, even on popular “how to” websites like E-How. The miracle cure of baking soda and vinegar goes on and on and on. The story that I hear is usually accompanied with tale of how the drain was slow or clogged and how they had tried all kinds of mind-boggling remedies. I have heard about pouring boiling hot water in a drain, crushing two Alka-Seltzers putting them in a drain then pouring in vinegar and a host of other alleged fixes for clogged drains. You would be far better off taking the two Alka-Seltzers yourself then wasting them in a drain. I do understand that a clogged drain is a headache but the drain sure doesn’t. The most persistent of these drain cleaning legendary myths is the baking soda and vinegar combination.
I have mixed the combination once before many years ago when I was in Junior High School as part of my science fair exhibit when I made a baking soda volcano but never as a drain cleaner. I still remember the science lesson well behind the baking soda volcano and there really is nothing special in this lesson that would ever clear a clogged drain. Vinegar contains Acetic Acid, and Baking Soda is Sodium Bicarbonate, when combined there is a acid/base reaction where the two combine to form Carbonic Acid which rapidly breaks down becoming Water and Carbon Dioxide gas. The only thing that happens of any note is a foaming chemical reaction as the two combine in a chemical reaction. There is no miracle occurring that will ever unclog a drain. For more interesting results, I suggest adding red food coloring to the standing water in the drain. It produced spectacular results with my baking soda volcano with red lava pouring down the sides of the volcano.
I have seen the results of a customer repeatedly using the mixture of baking soda and vinegar in an attempt to clean a slow drain. After numerous attempts and finally the sink not draining at all the customer called me to clean the drain. I removed the p-trap and found it packed solid with a whitish grey sludge. The sludge was packing the solid from the sink to the wall with this solidly packed sludge. I worked for quite a long time jamming a long screwdriver through the sludge breaking out chunks and scooping away finally I got it clean enough that I could pass a wet rag through the drain pipes and scrubbing them clean after several passes. I then snaked the line in the wall then put the drain back together and the sink drained nicely.
While limited results may occur with some commercial drain cleaners and also bacteria and enzyme based drain care products the only real solution in most cases to hire a plumber that cleans drains and have the drain snaked clean.