Written and maintained by CASRAI Editorial Board
Last updated
General product and storage information only; this page is not medical advice and does not replace a product label, safety data sheet or your facility’s policy.
Short answer
Household-strength sodium hypochlorite (bleach, 3 to 6%) does not stay at its label strength forever. One manufacturer statement relayed by Weill Cornell EHS says a bottle keeps about 6 months at 50 to 70 °F and then loses roughly 20% of its strength per year. Heat, light and air speed the loss, which is why CDC/ATSDR guidance calls for cool, air-tight, dark storage.
Definition and scope
This page covers undiluted (“stock”) bleach, meaning sodium hypochlorite as sold in the bottle. It does not cover preparing or using diluted solutions, which have a much shorter useful life; see how to make a 10% bleach solution and bleach concentration for those. Calcium hypochlorite is a different product and is not covered here.
Sodium hypochlorite shelf life
Bottles of consumer bleach typically carry no expiration date, only a production date code. According to the Clorox product specialist quoted by Weill Cornell EHS (a 2003 statement about one product, Clorox Ultra Regular), the code can be decoded to estimate the bottle’s age. A figure from one manufacturer’s product is not a universal rule for every brand or concentration.
How bleach loses strength and what sources say about storage
Bleach storage
The archived CDC/ATSDR Medical Management Guidelines for hypochlorite state that hypochlorite solutions should be stored at a temperature not exceeding 20 °C, away from acids, in well-fitted air-tight bottles away from sunlight. The EPA-accepted label wording summarised in CASRAI’s bleach concentration guide is similar: a cool, dry area, away from direct sunlight and heat, to avoid deterioration.
The Clorox statement relayed by Weill Cornell EHS adds that storing at room temperature is recommended, that bleach can be stored for about 6 months at 50 to 70 °F, that afterwards it begins to degrade at a rate of 20% each year, and that storage well above 70 °F could cause it to lose effectiveness.
Stock, diluted and labelled storage compared
Three different “clocks” are often blurred into one number. Each row below is taken from a single source.
| What is being described | What the source says | Source |
|---|---|---|
| Stock bleach, one manufacturer’s product | About 6 months at 50 to 70 °F, then about 20% loss per year; production date code, no expiration date | Clorox product specialist (2003), relayed by Weill Cornell EHS |
| Hypochlorite storage conditions | At or below 20 °C, away from acids, air-tight bottles, away from sunlight | CDC/ATSDR Medical Management Guidelines (archived) |
| Diluted hypochlorite in tap water, pH above 8, closed opaque plastic container at 23 °C | Can lose up to 40% to 50% of free available chlorine in 1 month | CDC Disinfection and Sterilization Guideline, Chemical Disinfectants |
| Sodium hypochlorite solution in a closed brown bottle | Does not decompose after 30 days | CDC Disinfection and Sterilization Guideline, Chemical Disinfectants |
| Label storage statement | Cool, dry area, away from direct sunlight and heat, to avoid deterioration | EPA-accepted label wording, as summarised in CASRAI’s bleach concentration guide |
Editorial arithmetic, not a measured value: if a 6% product lost strength at the 20% annual rate quoted above, it would be about 4.8% after one year (6 × 0.8). The 20% figure comes from one manufacturer statement about one product, so treat the result as an illustration of how a label percentage describes the product at manufacture, not as a prediction for a particular bottle.
Where it matters for labs, clinics and supply decisions
A record-keeping checklist that follows directly from the sources above:
- Production date code: the manufacturer statement says this is what bottles carry in place of an expiration date.
- Storage temperature: compare the storeroom with the 20 °C ceiling in the CDC/ATSDR guidance and the 50 to 70 °F range in the manufacturer statement.
- Container: air-tight and shielded from sunlight; CDC reports brown-bottle stability for 30 days.
- Separation from acids, per the CDC/ATSDR storage statement.
- Diluted solutions: they decay much faster than stock, as the CDC figure in the table shows. Details are in the 10% bleach solution guide.
Disinfectant type, dilution life and expiry vary by product; see types of disinfectants and always follow the product’s own label. For storage of chemicals alongside other spill-response supplies, see chemical spill kits.
Common misunderstandings
- “Bleach stays the same until it is empty.” The sources describe gradual degradation, faster with heat.
- “One shelf-life number applies to everything.” The 6-month and 20% figures belong to one manufacturer’s 2003 statement; the CDC 40% to 50% monthly loss applies to diluted solutions, not stock.
- “Diluted and stock bleach age alike.” Diluted solutions in the CDC example lose up to half their chlorine in a month.
FAQ
Does bleach expire?
Bottles are not given an expiration date, but the sources describe a slow loss of strength: about 20% per year after roughly 6 months, per the one manufacturer statement (Weill Cornell EHS, 2003).
How long does unopened bleach last?
The only sourced figure here is that one manufacturer’s product keeps about 6 months at 50 to 70 °F before degrading by about 20% a year. Other brands and concentrations are not covered by that statement.
Does heat shorten bleach shelf life?
Yes, according to the sources. The manufacturer statement says storage well above 70 °F could cause loss of effectiveness, and CDC/ATSDR guidance sets a storage ceiling of 20 °C.
How should sodium hypochlorite be stored?
CDC/ATSDR guidance: at or below 20 °C, away from acids, in well-fitted air-tight bottles, away from sunlight.
Sources
- CDC/ATSDR, Medical Management Guidelines for Calcium Hypochlorite and Sodium Hypochlorite (archived page, last reviewed October 21, 2014): https://wwwn.cdc.gov/TSP/MMG/MMGDetails.aspx?mmgid=927&toxid=192. Date checked: 2026-10-30.
- CDC, Chemical Disinfectants, Disinfection and Sterilization Guideline (page dated November 28, 2023): https://www.cdc.gov/infection-control/hcp/disinfection-sterilization/chemical-disinfectants.html. Date checked: 2026-10-30.
- Weill Cornell Environmental Health and Safety, “How long does diluted bleach last?” (relays a February 6, 2003 email from a Clorox product specialist about Clorox Ultra Regular): https://ehs.weill.cornell.edu/faq/how-long-does-diluted-bleach-last. Date checked: 2026-10-30.
