You find a jug of bleach under the sink, maybe a bottle of Clorox from a bulk stock-up during flu season or a move-in cleaning spree. Does bleach go bad?
The short answer: Yes, and probably faster than you’d expect. Clorox’s own guidance states that properly stored disinfecting bleach lasts up to a year, and after that, the active ingredient breaks down fast enough that it’s no longer strong enough for EPA-registered disinfecting or sanitizing uses. There’s no printed expiration date on the bottle; instead, Clorox stamps a production code you can decode to find out exactly how old it is. And if you’ve ever diluted bleach with water for a spray bottle, that mixture has an even shorter clock: about a week before it starts losing real disinfecting power.
Key Takeaways
Full-strength bleach, unopened: Good for about 1 year from the manufacture date when stored properly, per Clorox’s own guidance. More precisely, Clorox’s own figures split this in two: the 6% concentration required for EPA-registered disinfecting is guaranteed for about 6 months, while the product remains fine for general cleaning and laundry for up to a year.
There’s no expiration date printed on the bottle, just a production code. Clorox provides its own instructions for decoding that code to find the actual manufacture date.
Diluted bleach solutions degrade dramatically faster. A typical bleach-and-water disinfecting mix can lose meaningful strength within about a week, not months, since diluting it also dilutes whatever stability the concentrated product had.
The active ingredient breaks down into ordinary salt and water. Sodium hypochlorite naturally decomposes over time, roughly 20% of its strength per year under good storage conditions, faster with heat or light exposure.
Clorox specifically manufactures its bleach differently by season, adding more active ingredient to batches made in summer to account for hotter shipping and storage conditions accelerating the breakdown. Other brands may or may not follow the same practice.
Old bleach isn’t more dangerous from age alone, but never mix bleach with ammonia or acidic cleaners at any age. That combination produces toxic gas regardless of how fresh or old the bleach is.
Why Bleach Doesn’t Last as Long as You’d Think
Sodium Hypochlorite Is Chemically Built to Fall Apart
Household bleach is a dilute solution of sodium hypochlorite, the compound doing all the disinfecting and whitening work. Unlike a lot of the household products covered elsewhere in this series, sodium hypochlorite isn’t chemically stable over the long term by nature. It naturally and continuously breaks down into plain salt and water, along with a small amount of sodium chlorate, a decomposition process that starts the moment it’s manufactured and never stops.
Heat and light both speed this up significantly, which is exactly why bleach is always sold in opaque bottles and why storage temperature matters so much more here than it does f
