Chemical drain cleaning - acid, base or something else?

Question

There are industrial drain cleaners but according to my research on them, they are mostly overpriced bottles of simple chemicals such as sodium hydroxide.

Chemicals that can (theoretically) be used for drain cleaning also often already lay around your garage with no need to rush and buy dedicated drain cleaner. Either way, this question is what to use, specifically from safety point of view. Here are some options:

• Acids - I know for sure that sulfuric acid is common drain cleaner base ingredient. However acids tend to react with a lot of metals. Sulfuric acid is relatively safe, but also not exactly efficient. Should a reaction with metal occur in the pipes, you're in for a nice hydrogen explosion (worst case scenario).
• Basic hydroxides - Probably only sodium hydroxide falls in this category (as far as drain cleaning is concerned). It leaves most metals alone, but aluminium violently displaces sodium from the molecule which means any alumunium surfaces will be destroyed by NaOH solution. This is a big concern before using this.
• Chlorine based house cleaners - I'm not sure if those are commonplace everywhere, but in Czech republic those are very common and universally used to disinfect anything. Due to this, they are always at hand, but how efficient are they at cleaning the drains and pipes is not clear to me.

As a special award for efficiency combined with lethality (to the user), I nominate

• Piranha solution - a combination of sulfuric acid and hydrogenium peroxide. Eats almost everything organic (that is, everything that can normally be dehydrated) and violently corrodes metals. The latter is the lethal part, but it would be #1 choice for pipe system that is guaranteed to be 100% plastic as long as proper venting is provided and concentration is low.

I would like someone with practical experience and knowledge of how plumbing works and how clogs form to give me some insights what is the best (safety comes before efficiency) solution.

I would like to keep this as general as possible for the sake of future visitors, but I want to make clear that it's not just drain that is clogged but also part of the plumbing. The drain was cleaned and still doesn't consume sufficient amounts of water.

Answer 1

Many of the commercial products are buffered in some way to try and reduce the impact on metals, since DWV plumbing may commonly be made from copper, brass, lead, or iron, as well as plastics. In the USA, aluminum is not, to my knowledge, a common drain pipe material.

Sodium hydroxide (lye) is primarily of use against grease based clogs, as it turns the grease to soap. Of course, it only turns the grease it contacts to soap, so if it flows past the clog it will only affect a small amount of a grease clog.

Boiling (or at least very hot) water is another approach, though it is not an approach to use on a toilet (commonly sealed to the base with a wax ring.) Adding sodium bicarbonate (baking soda) or sodium carbonate (washing soda) can add some of the saponifying effect that lye has while being much safer for you than handling lye.

In general, if you have cleaned out the trap and still have a clog in the drain lines beyond the trap, mechanical means (a drain snake) are much more likely to solve the problem than chemical solutions.

Hair is, by far, the most common component of most clogs. There are some drain cleaners which purport to be specifically formulated to attack it - from what I recall, independent test results were not encouraging, perhaps because hair in a drain clog is coated with a variety of other substances. Physically removing it works.

Acids can indeed affect metal pipes badly - I've recently seen a copper drain line where 25% of the diameter was just gone due to acid corrosion.