Bleach Shelf Life

[Parawood]

I was just on Comcast's Fansite and noted an interesting article about bulk shopping stores. It stated not to purchase bleach in large quantities as it starts to degrade after six months.

Does anyone have any insight to this?

Parawood

[chem geek]

This depends on the quality of the bleach, it's concentration, and the temperature at which it is stored. The table at the bottom of this link gives half-life times for various concentrations of bleach or chlorinating liquid at different temperatures. For 6% bleach at 75ºF, the half-life is around 800 days or over 2 years. At 90ºF, it's around 260 days so after 6 months the concentration might drop to around 4% or so.

Note, however, that this is high-quality product. Clorox Regular bleach might be OK, but an off-brand Ultra bleach might not. Nevertheless, keeping bleach for more than a year even at room temperature is probably not a great idea, but you could always measure its strength to be sure.

With 10% or 12.5% chlorinating liquid, the degradation rate is much faster -- roughly 4 times faster.

[PaulR]

I get 12.5% from a place that takes delivery twice a week, so it's fresh. The last gallon of my previous batch was 6 weeks old (temps ranging from mid-60s to around 90) and seems to have degraded to maybe 9.5%.

--paulr

[quantumchromodynamics]

I don't see any reason to buy in huge quantities. You can always get more. I would say that you should probably not get more than you will use in a 60 day period.