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I used drain opener (sodium hydroxide and sodium hypochlorite) in an RV and accidentally caused it to drain out (mixed about 1:10 with water) onto concrete below.

There is a fairly strong smell.

How quickly will these chemicals decompose?

What will they decompose into?

How fast will the smell go away?

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  • $\begingroup$ Was this liquid drainer cleaner or solid stuff? I'm guessing it's in solution, but want to make sure because Crystal Drano also includes aluminum metal which would change the answer. $\endgroup$ Apr 7, 2016 at 20:42

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The sodium hydroxide will not decompose appreciably, and leaves an area of concrete dangerously caustic. A person or pet walking across it could suffer serious burns.

You can neutralize the alkali with a mild acid such as vinegar or citric acid. Vinegar is only 5% acetic acid, so you'd need about 20 times as much as the amount of drain cleaner. Too much acid will attack concrete, so use pH indicator strips (e.g. for fish tanks or swimming pools) to adjust pH to neutral (about 7).

During the neutralization, a bit of chlorine gas will be driven off from the hypochlorite, but that smell should no last long. Any other smell would be from waste in the drain... that might last quite a while.

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    $\begingroup$ >The sodium hydroxide will not decompose appreciably, || It will catch CO2 from air over time. While not strictly 'decomposition', this still renders it less harmful. And advising to acidify hidrocloride solution... no. Just, no. $\endgroup$
    – permeakra
    Apr 7, 2016 at 19:09
  • $\begingroup$ There is little hypochlorite in drain cleaner, not "hidrocloride". A little chlorine gas may be given off, but not much. $\endgroup$ Apr 7, 2016 at 22:50
  • $\begingroup$ @permeakra Could always use a little sulfite or bisulfite, right? Slightly harder to come by, though. Metabisulfite is easy if there's a wine store nearby. $\endgroup$ Apr 8, 2016 at 3:15
  • $\begingroup$ True, or any other mild acid or acid salt. Vinegar was suggested because it's relatively cheap and readily available. Carbonated water (seltzer, tonic water etc.) would also work well, and have the virtue of no smell (an excess of vinegar would leave the floor smelling like pickles). It is so weak, though, that a large amount might be needed. $\endgroup$ Apr 8, 2016 at 4:01
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    $\begingroup$ Medical stores may have some thiosulphate, which should work nicely on neutralizing active chlorine. And no, acidifying bleach (hypochlorite solution) is a cheap lab-grade way of obtaining chlorine. It may be much, and, without proper ventilation, it may cause serious chemical burns of respiratory system. Bad idea. Actually, acetic acid plus chlorine is doubly bad idea, because chloroacetic acid. Suggest oxalic acid at the very least - it is both a reducing agent and a mild acid. Citric acid is not safe in this setup, unfortunately. $\endgroup$
    – permeakra
    Apr 8, 2016 at 8:43

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