Sodium Hydroxide and Plastic

  • Thread starter Felix83
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I have some crystallized sodium hydroxide drain cleaner that I want to use on my bathroom sink drain, but I just put in a plastic drain and the trap is plastic as well. The clog is past the trap, somewhere deeper. So will the NaOH be alright with the plastic? Not sure exactly what kind of plastic - I'm guessing PVC. Thanks.


Staff Emeritus
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One chemical compatibility matrix - but its limited - Hydroxide

Somewhat better compatibility matrix -

In my experience, PVC is compatiblel with NaOH and other strong alkalis.

However, I would recommend that you simply remove the P-trap and clean out the clog. If the drain is in the bathroom, then I presume the clog is mostly hair and soap. Dissolving the hair is usually what unclogs the drain.

In a kitchen however, grease (or animal and some vegetable fat) is the cause of the clog and NaOH will not necessarily solve the problem.
The drain-cleaning action of NaOH is mainly based on the heat it releases when it dissolves in water. If grease is the cause of the problem the heat should soften it and if hair is the problem the [tex]OH^{-}[/tex] should dissolve it.

Incompatibility with plastic may be caused by the high temperatures involved, at room temperature pvc should be fine. At 100 degrees celcius that might not neseccarily be the case.

btw, would
[tex][CHCl-CH_{2}]_n + nOH^- \xrightarrow{heat} [CH_2O-CH_2]_n + nCl^-[/tex]
be possible?
Last edited:

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