Just as the title asks, is it safe to use products like Liquid Plumr or Drano in a Septic system?

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    Since you say it is a slow drain in the bathtub, I highly recommend trying those plastic barbed hair clog removers (commonly found brand Zip-it or generic) if you haven't already. It works better than any chemicals I've used for alleviating hair clogs. Commented Oct 30, 2018 at 17:13
  • @UnhandledExcepSean Those things work great if the clog is in the first couple of feet. Beyond that you need chemicals or a real snake. Commented Oct 30, 2018 at 17:24
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    @manassehkatz completely agree, but if the only fixture draining slowly is the tub, a build up of hair at the drain seems most likely to me. Commented Oct 30, 2018 at 17:27
  • @UnhandledExcepSean Agree on the cause. But while I have a bathroom sink where various gadgets (including a bent wire hanger) can get the clog out (except one time recently where I did have to snake it) I have a tub that almost always needs a good 10' or more of snake to get to the real clog, and on that tub the chemicals often help too. But the Zip-it type stuff just isn't long enough. Commented Oct 30, 2018 at 17:36
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    I think PVC or ABS drains would be damaged by boiling water. Commented Oct 30, 2018 at 19:11

3 Answers 3



As a one-off use, Drano® is fine provided you aren't cleaning your floor or doing a couple loads of whites on the same day.

What independent studies say:

According to a 2004 paper by Cornell researchers titled "Household Chemicals and your septic system", despite the assertions of the corporations making Drano® and Liquid-Plumr®, these products can indeed destroy the beneficial bacteria in your tank. If used in excess, or in combination with other cleaner such as bleach you may encounter problems.

Further, the 1987 study preformed by Mark Gross for the Arkansas water resource title "Assessment of the Effects of Household Chemicals Upon Individual Septic Tank Performances" claims that for a 1,000-gallon septic tank, the maximum allowable maximum daily dosage of common cleaners is as follows:

  • Liquid hypochlorite bleach: 1.3 gallons
  • Pine cleaner: 2.5 gallons
  • Crystal drain cleaner: 0.65 ounces

Research Notes:

Many plumbers claim that one should worry about the impact of what ever it is that caused your drain in the first place (fats, sanitary napkins, large solids, washing machine lint), than the use of the drain cleaner it self. For this reason, it is preferable to snake your drain rather than clear it with a Drano®.


According to Drano

Will Drano® products harm my septic system?

No, all Drano® products are septic safe drain cleaners and will not upset the bacterial action in septic systems. Follow the package instructions for the right amount of product to use. Use Drano® Max Build-Up Remover on a monthly basis to replenish the bacteria in the septic system that help break down toilet paper and organic matter in pipes.

And Liquid Plumr

Is it safe to use Liquid-Plumr® products if I have a septic system?

Yes. It’s safe to use Liquid-Plumr® products if you have a septic system. The ingredients degrade rapidly and will not harm the bacteria in your tank.

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    Hmmm. Drano is "safe" as long as you repeatedly use this second product to recover the bacteria that the first product decimated... Commented Oct 30, 2018 at 21:25
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    Apart from "safe" you may question whether it's "effective". My understanding (correct me please, those who know) is that it causes an exothermic reaction and the heat thins out the grease in your plumbing. Unless congealed grease is in fact the problem, as opposed to hair, toothbrushes, cutlery, plastic toys (yes I've found all of these), it may do no good at all.
    – user689
    Commented Oct 30, 2018 at 21:57
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    The main component in many drain cleaners is sodium hydroxide. The crystals that are coated use an aluminum the 2 react violently and do create some heat and a boiling action but the sodium hydroxide is the work horse at dissolving soap , hair etc,, I am not sure about the liquid types but if heavily used it will kill the good stuff in the tank then solids build up and that's what kills the drain field
    – Ed Beal
    Commented Oct 30, 2018 at 23:06

In what way are you using "safe"? It is not supposed to damage the pipes where some stronger drain cleaners will etch metal pipes. As far as chemicals in the tank it may affect the bacteria until diluted but this is true with even soap and laundry detergent. Over all I would expect infrequent use and that should not damage the system so in that regard I would say it is safe.

  • It would just be used on, hopefully, very infrequent occasions to clear any potential blockages. For example, my bathtub has been draining slowly for a couple weeks now and I would like to use it and see if it can clear up anything in the pipes (plastic).
    – Programmer
    Commented Oct 30, 2018 at 13:33
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    There are some "enzyme" type cleaners which are useless for a blockage but can work in some cases quite well for a slow drain. My hunch is they would be far less of a problem for a septic system. Commented Oct 30, 2018 at 14:59

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