Bought some drain cleaner from my local hardware store, the guy at the counter said its powerful stuff that barbers use to clear hair from drains. Said to not put my head above the drain while using it or breathe it in (standard for most household chemicals), open a window and use about 150ml, let it sit 5-10 mins then rinse with cold water, simple enough.

Go to use the stuff today on a tub/shower drain. I'd just finished a shower and got dressed, so there could have been some residual lukewarm water in the drain. As soon as I tipped the stuff into the drain, it bubbled violently and created some reddish-orange stains around the drain (since rinsed off) and some dark grey staining on the drain ring itself. Frantic googling revealed that it was sulfuric acid.

I started running cold water from the tap about 15 seconds after this reaction (googling while water was running) since that was the advice in the first place and rinsed the inside of the tub with cold water numerous times from a bucket and with detachable shower head, rinsing even the walls next to the shower that were most likely not even in contact with the bubbling drain (though there was some steaming and spitting, so something could have spattered).

the Window was open and I didn't smell anything during or after. I left the cold water run for about 5 minutes after the initial use, and checked on the thing and run water a few more times and aside from the dark grey staining, everything seems to be normal. It was sulfuric acid it turns out. If I had to guess - I would say I got maybe somewhere between 1-2 ounces/30-60ml (if that) out of the bottle. The reaction was so immediate that I stopped right away.

I live in a foreign country and can't read all labeling which is why I got the full download from the gent at the hardware store. Wasn't warned to expect bubbling/boiling so make sure all the water was cleared from the drain or wear PPE so guessing that's what caused the initial violent reaction. I did not use gloves or glasses - very stupid I know, but I would not have used the solution at all if I'd known. I did not get any on my skin but rinsed my hands many times regardless. I also threw some baking soda down after I'd rinsed the tub out many times and run the water for a very long time (that was probably at least 60-90 mins after initial use). Putting the soda down did not generate any reaction aside from absorbing water. nonetheless I scooped it out after about 45 mins bagged it a put it in the trash outside.

I called poison control about potential exposure on skin/inhalation - they said if it were there, I'd know by now (approx 45 - 60 mins after initial use), but based on the situation its likely that there was no exposure. I even changed and washed my clothes and my towel and bathmats that were nearby just in case (as was recommendation on many chem company websites/MSDS)

I won't be using any more of the acid, but is there anything else I should do to clean/clear the acid that was used? I immediately capped the bottle and set it down on the tile near the tub - but if there were a drop or two that happened on the tile or floor, what danger could that bring.

I'm freaking out a bit about how I was no naive and did not take the time to translate the label. Wondering if there are any future dangers to consider if its left in small amounts on the surfaces around the drain? most of the MSDS are geared toward severe spills/exposure/inhalation rather than smaller applications.

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    $\begingroup$ Well, maybe you didn't notice that drain cleaners are all very aggressive by design - they are supposed to react with stuff in the drain. $\endgroup$
    – Mithoron
    Jun 4, 2023 at 20:03
  • $\begingroup$ I am aware - I just didnt expect such an immediate and strong reaction and now understand this product isnt really for household applications unless in the hands of a qualified professional. $\endgroup$
    – sadhunk
    Jun 4, 2023 at 20:10
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    $\begingroup$ I wouldn't say so, NaOH is hardly less dangerous. You just need to be careful and definitely not panic. You only saw a reaction that was supposed to happen inside the plumbing - where it wouldn't be visible. $\endgroup$
    – Mithoron
    Jun 4, 2023 at 23:19
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    $\begingroup$ An MSDS will tell you what safety precautions might be necessary with respect to handling and disposal. Is your question what reaction occurred? Personal medical questions are not accepted on the forum. If you develop symptoms from use of the product contact a medical practitioner. $\endgroup$
    – Buck Thorn
    Jun 5, 2023 at 5:09

1 Answer 1


It's odd that $\ce{H2SO4}$ was used as a drain cleaner, since it attacks metal pipes, and is not effective at saponifying fats. Double-check that the cleaner was not $\ce{NaOH}$ solution.

That said, $\ce{H2SO4}$ is readily soluble in water, and, once diluted, was safely neutralized with baking soda.

However, a concern is that plumbing might have been damaged. Check for leaks, and possibly, use a small camera to check for holes in the drain pipe, or where flange meets the drain and tub or base.

  • $\begingroup$ Apparently there does exist a drain cleaner, in the USA, that is concentrated sulfuric acid. Enough said … $\endgroup$
    – Ed V
    Jun 4, 2023 at 19:14
  • $\begingroup$ It was sulphuric acid, I translated the label and it said "based on sulphuric acid" but does not give a chemical solution or % concentration, but I'm guessing based on my digging its around 95%. I could not find an MSDS for this exact product online, only similar solutions. I can access my tub plumbing from below and I see that after running water for a very long time, there is a known drip but thats all. Its PVC piping but may just call a plumber out to double check anyway. Thanks $\endgroup$
    – sadhunk
    Jun 4, 2023 at 19:19
  • $\begingroup$ This is in europe, but I did find this common and available for extreme blockages and industrial applications. to be frank, I can't even believe they sold it to me at a regular shop $\endgroup$
    – sadhunk
    Jun 4, 2023 at 19:21
  • $\begingroup$ The most surprising phenomena was the "violent bubbling" and the "dark grey staining" that happened when you used your stuff for the first time. This is due to the stuff that was previously deposited in the drain. It is not due to sulfuric acid alone, or caustic soda alone. What was this drain used for, previously ? $\endgroup$
    – Maurice
    Jun 4, 2023 at 19:22
  • $\begingroup$ its a household shower drain - that's all. occasionally used to pour other standard household cleaners down, but by that I mean CLR or floor cleaner for mopping. That was several months ago at the most recent. I did read on a plumbing forum that its pretty common for the acid to discolor nickel finish by turning it black. The bubbling, I am only guessing was because of the water left in the trap and soap/hair that could have been there. Also said this on the plumbing forum. $\endgroup$
    – sadhunk
    Jun 4, 2023 at 19:30

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