Me... wrote:I keep wondering about this apparent marvel of modern chemistry and I guess water and costs must be different in various parts of the world.
Bleach, 5%-6%, is weak liquid chlorine, 10%-12%, and as far as I can see is not half the cost. I also have to wonder about the amount of other "filler(s)" that might be in the bleach.
Using a liquid chlorine product would drive the pH high in which you would be looking to use Muriatic Acid or such, not pH up or Soda Ask or Borax or whatever.
And yes, Alkalinity Up is nothing more than food grade Sodium Bicarb buts its a long term purchase. Grab a 25 kilo bag of it and store it properly. I don't foresee getting 50 boxes of Arm & Hammer from the grocery store that cheap.
Plus, the grocery stores make enough money, support that local guy you call on for your problems. That Vegi guy in the corner store ain't gonna help ya much when your pool stops working LOL.
In some areas, bleach is less expensive than chlorinating liquid for the same amount of Free Chlorine. A cost comparison of chlorine sources is here
I buy 12.5% chlorinating liquid from my local pool store and it costs $3.65 per gallon. This is equivalent to a 3/4-gallon (96 fluid ounce) 6% bleach at $1.44. Sometimes bleach is sold for close to $1 per jug so you can see that sometimes it can be less expensive. As you say, it very much depends on local pricing. I do buy from my local pool store not only because their price is reasonable, but I do like to support them and I want to carry less weight when I buy the chlorine. Also, I bring back the bottles and they reuse them which is even better than recycling.
You do have to be careful not to get inexpensive bleach since it may be <3% and not very pure so has more excess lye in it. This is even true for many store-brand Ultra bleaches at 6% since their pH is sometimes 12.5 or so. Clorox Regular unscented bleach has a pH of around 11.4 so has an insignificant amount of excess lye in it (i.e. the high pH is buffered by hypochlorite ion) and it is intended to be used as an alternative source of chlorine for pools which is why it has "5.7% Available Chlorine" on the bottle. There is a small amount of sodium polyacrylate in the bleach in order to bind to impurities such as iron and manganese.
It is not true that use of hypochlorite sources of chlorine, including bleach and chlorinating liquid, have the pH rise over time. See this post
for technical details. It is true that the ADDITION of a hypochlorite source of chlorine makes the pH rise, but the USAGE or CONSUMPTION of chlorine is an acidic process that brings the pH back down. The net use of hypochorite sources of chlorine (bleach, chlorinating liquid, Cal-Hypo, lithium hypochlorite) is nearly pH neutral.
The source of pH rise in most pools is having the Total Alkalinity (TA) be too high since TA is mostly a measure of bicarbonate and pools are over-carbonated in order to provide a pH buffer and to protect plaster (via calcium carbonate saturation). The pH rises when carbon dioxide outgasses from the pool (see this chart
). At pH 7.5, the equilibrium amount between carbon dioxide in the air vs. pool water would only have a TA of 9 ppm with no CYA (or 18 ppm TA with 30 ppm CYA). In my own pool during the summer, I use around 1 ppm FC per day and in theory if the chlorine didn't get used up the pool's pH would rise by 0.4 units in just one week but my pool's pH is very stable only rising around 0.2 in about one month because the usage/consumption of chlorine is acidic. I keep my TA around 80 ppm and I also have an opaque electric safety cover so that mostly eliminates outgassing (and evaporation) though the pool is open for an hour or so for use every day.
Finally, BBB isn't really about using store-bought chemicals. It's more of a philosophy about education and truth and being well-informed so that one can make rational decisions based on facts. One can certainly continue to use Trichlor pucks, for example, since they are convenient, but at least one will know how fast the CYA is expected to climb, the need for algaecide or phosphate remover (unless the FC is raised proportional to the rising CYA), the acidity of the pucks, and the costs of pH adjustment.