Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Disposing a Bleach Solution

  1. Nov 17, 2011 #1
    Hi everyone.

    A quick question. How do I dispose of an old bleach solution? I suspect pouring it down the drain or on the ground is not a good idea.

    I made a strong bleach solution several months ago to do some heavy cleaning (long story), and the remainder has just been sitting in a bottle. I need to make a fresh batch to do some more heavy-duty cleaning, and obviously I want to use the same spray bottle. So I need to get rid of the old batch, because I heard the stuff loses its strength after a while. What do I do?

  2. jcsd
  3. Nov 17, 2011 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Why wouldn't you pour it down the drain? Bleach is used for cleaning drains and toilet bowls.
  4. Nov 17, 2011 #3
    Lol, I didn't know that (I'm a man! That's my excuse.). Ok, thanks, I'll just pour it down the drain then.
  5. Nov 17, 2011 #4


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Men.. Just make sure there is no urine in the toilet bowl when you dispose of it.
  6. Nov 17, 2011 #5


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Not sure what a "large amount" is, but before you pour it down the drain: are you on a city sewer system, or a septic system? Large amounts of bleach may not be good for septic systems, which rely on microbes to keep running properly.
  7. Nov 17, 2011 #6
    It's just table salt with an oxygen right? Just run some hot water and pour it down the drain slowly. Unless you have a septic system, in which case I have no idea what to do with it.
  8. Nov 17, 2011 #7
    speaking of this, what is the best way to neutralize a bleach solution without creating an inhalation hazard? i imagine something organic for it to degrade, but what?
  9. Nov 18, 2011 #8
    Well it's a bit late since I've already poured it down the drain. It was about 500ml, or a pint. It was a few months old, it didn't even smell of bleach any more.

    I'm on the city sewer system, btw. And why shouldn't there be any urine in the toilet?
  10. Nov 18, 2011 #9


    User Avatar

    Staff: Mentor

    Most likely it is a solution of hypochlorite. So yes, it can decompose to NaCl and oxygen, but usually it has high pH and emits chlorine.

  11. Nov 22, 2011 #10
    Strong is a relative term! typical household bleach is 5.75% maximum active "Cl", and a strong solution is generally 1/4 cup per gallon (2oz in 128 oz) ~less than 1000 parts per million! Running it down the sink with a few extra gallons of water and it becomes below 100 ppm, not something I would worry about -even in a septic tank with typically a 2000 gallon capacity and as much organic reducing activity as you could imagine.

    If you want a strong active Cl content take swimming pool shock chlorinating tablets and dissolve in water (often 50% active Cl)- they have a lot of insoluble materials and so are not nice at cleaning without much residue- they would also destroy your spray bottle innards. Works great on cleaning decks of algae and mildew!

    Active Cl is destroyed in a redox reaction with a reducing agent- the wastewater treaters have to do it and also keep the water from being so deoxygenated that fish are killed - two chemicals are used, a sulfite or bisulfite, and ascorbic acid (vitamin C)- sunlight on a flowing stream will remove 20-5-% of active Cl for 100 ppm waste water.
    Sulfites are cheaper but are prone to deoxygenating the water- they are also toxic in their own right, so too much of a good thing is actually bad since it won't find active oxidizers in the sewer water- excess bleach is bound to run into plenty of reducing compounds in the sewer!
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook