gullzway said:
As far as the bleach degrading, I don't know, but I wouldn't think in 2 Weeks it would lose much strength.
According to these data, around 10-12% loss in strength at 80oF over 2 weeks and maybe double that at 90oF......at least with 'commercial' 12.5% bleach
chlorine-degradation-due-to-heat-over-time-t24789.html
http://www.odysseymanufacturing.com/decomp_curve.htm
gullzway said:
Not too concerned as I get it from my work where we have two 3000 gallon tanks of 12.5% chlorine.
Yeah, I guess that helps.
The Purox bleach I get from Canadian Tire is stated to be 10.8% (guaranteed) on the label. The MSDS however states 7-13% sodium hypochlorite.
http://www.sissiboofarmsupplies.com/MSDS/Clorox.pdf
I can't believe it's that variable at production so probably they (Clorox Canada) produce at 13% and allow for a loss of up to 46% through handling, distribution and storage. So I reckon the 10.8% must be based on an average production-to-in-store interval of something like two weeks. The 7% then allows for a more gradual degradation over a period of months in-store.
I guess if you're getting your 12% stuff from a plant source you've got a head start. Also if you are dosing with a (semi) continuous feed, it's less of an issue, and you can regulate accordingly. But if, like me, you are single dosing a calculated volume of bleach, it's potentially more significant. For now however, the 5 or so 4L bottles I've bought have given the expected rise in FC ppm, so they must be around 10% at least. If I do continue using the Purox later in the season (assuming stocks last) I might be inclined to confirm the concentration and I don't think I'd stockpile.
Several years back CaOCl2 tested a batch and found it to be down to 8.5%:
practices-in-a-pool-store-piercing-the-veil-of-ignorance-t25345-20.html
Interesting that the MSDS for Clorox Ultra (6%) states a concentration range of 5-8%.
http://msds.flexoproducts.com:8000/MSDS ... X%2012.pdf
Which perhaps gives greater confidence that you are actually getting your 6%.
Also the evidence is that 5% bleach has something like 3X the half life of 10% bleach and 7X that of 15% bleach at temperatures ranging from to 75- 90oF
http://www.odysseymanufacturing.com/about_product.htm
So, I think if I was to consider a similar sort of regulated flow dosing system I'd maybe look at using a more dilute bleach solution, even if that involves filling up the feed reservoir more often.