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In our new house, we found that a previous owner installed a sump pump battery backup unit, which is nice. The battery in the system is like a car battery, but it's the kind where you initially add sulfuric acid to, and then periodically top off with distilled water.

However, the owner left behind the container of leftover sulfuric acid. The manual for the battery system says to never add more acid to the battery, only water.

So, what should I do with this acid?

  • Is it dangerous to keep in the basement? Will it emit bad vapor?
  • Can I keep it in case I need more if I buy a new battery in 5 years?
  • Should I dispose of it? How?
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    We've turned into a nation of lawsuit-happy wussies, which means that mikes' answer, below, is pretty much what you have to say. But Sulfuric acid is no more dangerous than gasoline, bleach, or even some drain cleaners (all pretty dangerous by today's standards) if you remember some basic chemistry and safety. Can't say anymore. Find an (ex) auto-mechanic who is over 60 and, after he stops laughing, he'll help you deal with the acid without needing to declare another EPA superfund site.
    – Brock Adams
    Apr 21, 2012 at 3:10
  • @Brock - I agree that mikes' instructions are pretty extreme, but the OP's questions indicate that he isn't familiar with basic chemistry. And, having grown up as the son of an analytical chemist, whose home lab contained some pretty nasty stuff, I can say that strong acids and bases (including Drano) scare the heck out of me. Without knowing that condition of the container, I wouldn't be willing to say "yeah, just toss it in the back seat."
    – kdgregory
    Apr 21, 2012 at 12:20
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    Depeinding on the density of the acid it is safe to dilute it with water and then drain it. Remember, always pour acid into water to avoid splash burns. Say its 1 litre of 5% then diluting it to 10 litres is safe. 1 litre of 50% will need ALLOT more dilluting.
    – Piotr Kula
    May 1, 2012 at 10:05
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    The answer from ShoeMaker neutralizing with baking soda is correct, but only if the battery acid is new. Used battery acid contains heavy metals such as lead sulfate which cannot go down the drain, even when the acid has been neutralized.
    – MorningCloud
    Jan 9, 2015 at 13:18
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    I store my spare H2SO4 in its original container, inside a glass bowl at the back of a shelf in the basement. The glass'll stand up in the unlikely event of bottle failure, and the stuff does come in handy for tough cleaning problems every few years. There's no kid problem here, otherwise it'd be securely locked away.
    – Wayfaring Stranger
    Jan 9, 2015 at 14:16

4 Answers 4

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I'm going to second mikes advice about wearing rubber gloves and safety glasses, especially if you can't guarantee that the container is properly sealed. If you get any on you, simply flush with lots of water, and apply a paste of baking soda and water to neutralize (I would flush first while someone else mixes the paste). For transport, just make sure that you have something that will keep it from tipping over.

OK, now to the reason I answered: places that you can take it.

The easiest is if your town or city sponsors a hazardous waste day or provides a hazardous waste dropoff (more likely in a large city). Call first to ensure that they take acids. Most will, especially acids that are commonly used in home improvement, such as sulfuric and hydrochloric (aka muriatic).

If you have a relationship with a repair shop, you can call and see if they'll take it (for use with batteries). They probably won't, and a stranger definitely won't, but it's worth asking.

A metal plating shop is another possibility. They probably won't accept it for use, but might dump it into their waste drum for a nominal charge.

Finally, if mikes scared you, there's Clean Harbors or similar companies. They'll come to your house and scare you even more, and you'll pay through the nose. But it will be gone.

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If you can not find someone to take care of the acid for you, it is possible for you to dispose of it yourself. this page which references batterycouncil.org which most discreetly describes the process outlined here that states:

  1. Gather together all the acid you need to dispose of and put on some sort of concrete pad. The high acidity may harm grass and soil, so try to do this in your driveway or on the patio outside. If you have batteries to dispose of, pour the acid out of the battery into a plastic container that will not break down in acid. If you are unsure, pour just a little in the container and see if there is any reaction before emptying the whole battery.

  2. Use rubber gloves and goggles anytime you are dealing with highly concentrated acids. Acid is harmful to the skin if exposed and especially to the eyes. If concentrated acid touches the skin, thoroughly wash the skin for five to ten minutes and then sprinkle with baking soda to neutralize any remaining acid.

  3. Fill a larger container half full of water. Slowly add some of the acid that needs to be disposed of and stir gently. Slowly add the baking soda, one tablespoon at time. The solution in the container will bubble and foam as the baking soda neutralizes the acid. Continue to stir as you add each tablespoon full. Once the bubbling and foaming is complete, test the solution by adding another teaspoon of the baking soda with stirring to see if any more reaction occurs.. When the reaction is complete, wash the solution down the drain and refill the container half way with water.

  4. Neutralize all the acid in the same manner as Step 3. Pour the neutralized acid down the drain. Follow the neutralized acid with lots of water. Continue to run the hose for five minutes after you are done and then turn off the water.

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    Finally someone who knows what they're talking about! Simple chemistry teaches one that acids and bases neutralize each other. Sulfuric acid is a common household acid, and baking soda is a common household base. While wearing eye protection and rubber gloves, the two can be mixed to produce a harmless liquid.
    – rjbergen
    Jan 9, 2015 at 18:47
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    I should also add that using a glass container for mixing is easier and safer than a plastic container. Glass is not affected by sulfuric acid.
    – rjbergen
    Jan 9, 2015 at 18:48
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Remove it from the basement while wearing safety glasses and rubber gloves and a rubber rain coat if you have one.If you can get a plastic storage container store it out side in that.You can try an auto supply store or battery specialtyshop to see if they will take it or anyplace that recycles metal as most take batteries.Some communities have a waste/chemical collection but are typically once a year.Once you find someone to take it then comes the problem of getting it there.You donot want this stuff inside of your car.Try to find someone with pickup or trailer.

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  • That's far too much work. It is sulfuric acid, but it's not going to kill you if you get some on you. A better bet would be to teach someone how to neutralize sulfuric acid using baking soda (acid-base reaction) and to recognize the signs of stong acid contact. Safety goggles are still a must, but other than that I wouldn't wear anything extra for handling the box.
    – rjbergen
    Jan 9, 2015 at 18:40
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Google household items with a high ph then dilute and sulfuric add together until the color changes and starts to get thicker then dump it down the drain this is ok at this stage it is not acid anymore it's called neutralizing I am a metal finisher I've been breaking down sulfuric acid for a long time this will be easy and not scary at all just dilute first and always add acid to water.

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    No. Mixing sulfuric acid with random alkaline chemicals will get random surprises. Stick with particular chemicals which itself is nontoxic and whose reaction products are also non-toxic.
    – Harper - Reinstate Monica
    Jul 26, 2018 at 6:23

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