Bleach as a Steriliser

Even if you use a bleach product with no sodium hydroxide (it’s there to aid cleaning action) you must never mix it with an acid. It will release chlorine gas. You don’t mix chemicals unless you know what you’re doing. The MSDS provides this sort of information.

There is no problem with using bleach solutions on things that will come into contact with your body. You rinse off the bleach after it has done its job. It leaves no residue.

@Albie, the sodium hydroxide is added to slow the decomposition of sodium hypochlorite into sodium chloride and sodium chlorate…namely to prolong the storage life of the product. It is usually added at very low concentrations .

Power force alpine thick bleach NaOH = 13 g/l; Power force liquid bleach 9g/l. I don’t regard that as insignificant.

@trevor3 I think you might be thinking of mould and mildew - terrible problems that we keep trying to fight with bleach. They’re a different kind of yuck.

Hey! I see that Choice has a new article about it. Great minds. :wink:

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There is more than one chemical marketed as bleach.

Traditionally, “bleach” usually meant a weak solution of sodium hypochlorite or a related chemical. In water, hypochlorite partially forms hypochlorous acid, which is a powerful oxidizing agent, and does the disinfection.

These days, although sodium hypochlorite is still available, many bleaches use a weak hydrogen peroxide solution as the active ingredient, marketing it as oxygen bleach (instead of chlorine bleach), environmentally friendly bleach, or colour fast/fabric safe bleach.

There are others, but these are the most common ones. There are a couple of reasons that usage instructions may be a bit vague. These chemicals work because they are highly reactive, which and they are rapidly consumed in the process. The amount of disinfectant required depends on how much there is for it to react with, so it’s always best to remove as many contaminants by rinsing, for example, before disinfection. Also, disinfection byproducts can be unpleasant. Foer example, the “chlorine” smell that people associate with indoor swimming pools is actually chloramine, formed by oxidation of ammonia by hypochlorous acid, and there is a lot of effort put into preventing organic matter getting into municipal water tanks not just because of the added cost of the extra disinfectant, but because carcinogenic trihalomethanes can be formed as a result of the disinfection process.

The other reason that usage instructions are a bit vague is that both sodium hypochlorite and hydrogen peroxide are unstable, meaning that they degrade over time. The rate of degradation varies with storage conditions such as temperature. The manufacturer doesn’t know how long you’ve had your bottle of bleach, or how you’ve stored it, so they don’t really know either the strength of the solution in your bottle or the level of reactive contaminants on the item you want to sterilize, making it a difficult job to provide one size fits all general guidance. Most of the liquid is just water, so when you use it, you can’t really tell if there is surplus active agent, or if it’s been completely depleted.

I would use a hydrogen peroxide based bleach rather than a hypochlorite based one for articles that people touch, because hydrogen peroxide breaks down into water and oxygen.

I don’t know exactly what you are sterilizing, but perhaps the manufacturer can provide some advice. Heat and UV radiation can also be effective in the right application, so it may be that boiling water or drying in the sun is a viable alternative. There may not even be any need for supplementary sterilisation beyond drying if the equipment is only used in chlorinated water.

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I’ve been using bleach as a means to sterilise drinking water when out. Chlorine liquid bleach is a good way to do this, a few drops per litre and some standing time are all that’s needed, bacteria are killed and the bleach evaporates out of the water.

The recommended dose is just two to four drops per litre, so bleach is definitely a potent antibacterial.

Thanks teddlesruss. You maybe the first to cotton on to my reason for posting this :slight_smile: Essentially if we are to use bleach, then lets use it properly, sensibly, and that is where Choice’s experts and scientist can educate us all. Propitiatory products contain bleach, with little guidance to its use, implying the more the merrier. So as you tell us just a few drops can help with drinking water, and my reckoning is maybe as little as half a teaspoon in a half litre of water seems to be sufficient for toilet cleaning.
However, media messages imply it isn’t a good thing to use at all. I’m keen on doing anything better to improve the environment, and Bleach may damage the underlying water system. Maybe there are better alternatives, if so, but then they need to be compared with the smartest dilution of bleach, ie, fit for purpose.
So still waiting for the Choice experts input!

One of the biggest problems with chlorine bleach is that it denatures and decomposes quite readily in normal exposure to air and sunlight. So when used in proper quantities rather than slathered onto anything, it’s quite environment friendly. As I said, you can make a litre of water bacteria free with only four drops of chlorine bleach, and it’s safe to drink after a few hours exposure to air and sunlight. So using a proper dilution is probably not going to do much harm.

But you’re right, it’s used in a lot of cleaning products and generally the manufacturers err on the generous side just to be sure their product will perform well, and so it needs us consumers to keep an eye an what we use and how we use it.

Unless you keep liquid bleach containing products in a temperature stable environment away from light, the bleach decomposes quite rapidly, and even under average cleaning cupboard conditions a bottle of liquid bleach is pretty weak after a year and probably beyond use after two.

I’ve also found that calcium hypochlorite powder is much more shelf stable and longer lasting in dry form than liquid chlorine bleaches, gives the same results, and also decomposes just as readily once made up into a solution. A little powder bleach can be made up pretty much as needed (and only as much as needed,) so you don’t end up throwing out as much decomposed bleach (and the attendant plastic jug it comes in) and therefore less pollution gets into the environment.

Agree @teddlesruss

Sodium hypochlorite is NaOCl. Since table salt is NaCl, bleach is very similar to table salt and reverts to table salt if left out. For example, the bleach in tap water will be gone if you let an open container of water stand for 24 hours. This is especially important if you have fish in an aquarium. Fresh tap water will kill fish because of the chlorine. But if you let the water stand for 24 hours, it is fine for fish.

It is unlikely to have any long term impacts on groundwater, unless it is pumped in very large volumes (which would be a criminal/environmental damage under state legislation). Even in this case, the groundwater will go saltier and may have a chlorine smell for a short period until the chlorine reacts with other ions in the groundwater and neutralised.

And it is pretty safe, so safe that people drink it every day in their tap water and swim in it in swimming pools.

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A post was split to a new topic: Do you think eucalyptus oil can be considered disinfectant?

Not so good for swimming pools though…