Does Bleach Expire? What You Need to Know for Storing Bleach


Author:
Last Updated: June 2, 2021

As a disaster prepper, I know that bleach is one of the most important items to have on hand for emergencies.  However, bleach also has a very short shelf life so isn’t really practical for stockpiling.

If you want to stockpile bleach but are unsure about how long bleach really lasts and how to store it, read this guide.

Bleach Expiration Date – The Quick Answer

Bleach does not expire in the traditional sense that it goes bad at a specific date.  Rather, bleach gradually breaks down and loses its strength.

If left too long, the bleach may become so weak that it is no longer effective.

To play it safe, bleach is usually given an expiration date of 6 to 12 months from when it was manufactured. The shelf life might be shorter or longer depending on how it was stored though.

How to Determine Expiration Date of Bleach

Bleach bottles do not list an expiration date on them.  However, they do list a manufacturing date on them.  To find this date, look for two lines of code on the bottle.  The first line includes the manufacturing date. The second line is an EPA and state ID code.

Here is how you decipher the manufacturing date code:

  • First two characters: This indicates which facility the bleach was made in. You can ignore these characters.
  • Second two numbers: These numbers tell you the year (last two digits of the year) the bleach was made.
  • Last three numbers: These tell you which day of the year the bleach was made.

Example Code: A921042

In this example:

  • A9 = Facility code
  • 21 = 2021
  • 042 = 42nd day of the year, which is February 11th.

Based on this manufacturing date, you could conclude that the bleach would be good until at least August 11th, 2021 (6 months) and probably good until February 11th, 2022 (1 year).

How to Store Bleach

Bleach goes bad faster when exposed to heat, air, light, and contaminants. To get the best shelf life out of bleach, then you’ll need to keep the bottle unopened and store it away from heat.

If you are able to keep the bleach at low temperatures (such as in a root cellar), it might be fine for up to two years. However, unless you have expensive lab equipment, there’s really no way to know how much the bleach degraded. For this reason, you should still aim to use up your bleach within 6 to 12 months of its manufacture date.

Can I store bleach in the freezer?

According to this report, bleach can be frozen and thawed without impacting its quality.  You might see some salt crystals form in the bleach as a result of freezing but these should dissolve when the bleach is mixed with water.

Despite this, most experts recommend against storing bleach in the freezer. While the bleach may remain usable for years, there aren’t any studies (at least that I could find) that look at the long-term impacts of freezing bleach.

Evaporation can occur even in freezers (as with lyophilization), so the bleach concentration could change. Likewise, the bleach could separate from the water during the freezing or thawing process, which could also impact its concentration.

Note that bleach has a lower freezing point than water.  The higher the concentration of bleach, the lower temperature you’ll need to freeze it. For example, 12% bleach freezes at -3F whereas 6% bleach freezes at 18.5F.  Most household freezers are set to 0F, so the bleach might turn to a slurry instead of a solid.

Can You Use Expired Bleach?

Because expired bleach may still contain some active sodium hypochlorite, you can still use it for things like washing your white clothes.

The problem comes if you want to use expired bleach for disinfecting.  While there may still be active sodium hypochlorite in expired bleach, you have no idea of knowing how much.  The amount might be too low to effectively kill germs.  For this reason, you should never use expired bleach for disinfecting surfaces or purifying water. (1)

Read more about how to purify water with bleach

How to Prolong Bleach Shelf Life

Key Points:

  • Heat will cause bleach to degrade faster.
  • No matter how you store it, bleach will start to degrade over time.
  • Higher concentrations of bleach degrade faster than weaker ones.
  • Once diluted with water, bleach degrades very quickly

Heat Causes Bleach to Degrade Quickly

One thing that is consistent across virtually all studies is that exposure to heat and light will cause bleach to degrade faster.  At temperatures of 40F, bleach is fairly stable.  At temperatures of 77F or above, bleach starts to degrade very quickly.

Other factors can also cause bleach to degrade faster, such as exposure to light. However, because bleach comes in opaque bottles, the temperature usually has the biggest effect on bleach’s shelf life in storage. (2)

Bleach Degradation Rate

One number which you will find on various websites is that, after 6 months, bleach degrades at a rate of about 20% per year.  It’s unclear where this number comes from.

While it may be true in some circumstances, bleach’s degradation rate may be very different depending on how it was stored and its initial strength.

For example, this study found that a 1:12 dilution of bleach degraded at just 5.24% per year.  Thus, this bleach was considered shelf stable for 23 months.  Another study found that 1.25% bleach solutions were stable for 12 months when stored in temperatures of less than 95F.  Yet another study found that 10% bleach degraded to approximately 7% after 120 days in storage.

Stronger Concentrations of Bleach Degrade Faster

The stronger the bleach is, the faster it will degrade.  For example, a bottle of 12.5% bleach might degrade to 5% over a year whereas a bottle of 5.25% bleach might only degrade to 4%.

This is important to know if you are planning on using bleach for things like disinfecting water.  It will be very difficult to dilute the bleach correctly when it has degraded by so much.  For this reason, 5.25% bleach might be preferable over 12.5% bleach for disaster preparedness. (3, 4,)

Bleach Degrades Very Quickly Once Diluted with Water

When you mix bleach with water, it reduces the pH of the bleach.  This causes the bleach to degrade very rapidly.  According to one report, diluted bleach has a shelf life of just 24 hours.  For this reason, you shouldn’t mix bleach ahead of time. (5)

Stockpiling Bleach for Emergency Preparedness

The standard advice for stockpiling bleach for emergency prepping is to rotate through it.   However, as a prepper who never uses bleach in her daily life (I refuse to wear white clothes!), this advice doesn’t apply to me.  Basically, any bleach that I buy for disaster prepping is going to get thrown away within a year.

I’ve had to decide for myself how much bleach I’m comfortable tossing each year.  Luckily, bleach is very cheap so it isn’t a huge financial loss.  Still, I’ve chosen to only keep a few gallons of bleach on hand.

However, I’ve also made sure to have some bleach alternatives stockpiled and have a good sanitation plan in place should SHTF.

How much bleach do you stockpile for emergency prepping? Let us know in the comments section below.

Leave a comment

  1. Useful information thank you.

    I did not realise it would last longer if cooled, I had assumed the cold ( unlike say chilling foods etc ) would have a negative effect. Pleased to be hopefully proved wrong.

    Seems to vary a bit but from base reading optimum store temperature seems to be between 10c – 25c ( about 50f – 75f ) although I would expect different brands and manufacturers to vary , possibly depending if it’s regular plain type bleach or one of the scented things some offer.

    Reply
    • The brand shouldn’t matter so much as the concentration of the bleach. And the lower end of the temperature spectrum is definitely better than 75F. It’s all so technical though (including things like what storage conditions the supermarket had the bleach at!) that I’ve mostly given up on stockpiling large amounts of bleach for prepping.

      Reply
  2. A buddy of mine who used to store bleach now stores powdered chlorine pool shock. I’ve been thinking of changing, as solid form must have a decent shelf life.

    Reply
  3. Your example code would mean the bleach was manufactured on the 31st day of the year, not the 42nd. January 31 not February 11.

    Reply

Leave a Comment