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In reading in the booklet that came with my Taylor test kit, it's claimed that lithium hypochlorite is the "Cadillac" of pool shocks, along with the Cadillac price. What makes it so much more $$ and, if it's the non-bleaching effect is has on vinyl liners then I guess a don't understand chlorine much? I thought chlorine was the same no matter the delivery mechanism?
It's more expensive because lithium is more expensive and the lithium hypochlorite is made by bubbling chlorine gas into a solution of lithium hydroxide. Sodium hydroxide is much less expensive so when chlorine gas is bubbled into that solution to make sodium hypochlorite the product is much less expensive.
The main difference, other than price, is that lithium hypochlorite is in solid form, usually granular/powdered, while sodium hypochlorite is a liquid. The other difference is that lithium hypochlorite has 35% available chlorine while sodium hypochlorite usually tops out at around 15% and usually 12.5% for chlorinating liquid or 8.25% for the latest bleach. So with sodium hypochlorite it's more weight to carry. However, the price per FC for sodium hypochlorite is far lower than that of lithium hypochlorite.
In water, however, it's all the same and one does not bleach out vinyl liners any more than the other unless one adds it too quickly in one place with no circulation. If you add any of the concentrated chlorine products slowly over a return flow with the pump running and then lightly brush the area where you added it to ensure thorough mixing, then none of the chlorine sources will be a problem (well, Trichlor granular might still be too slow to dissolve even after brushing, but all the others should mix reasonably quickly).
Generally speaking you should ignore a lot of what the pool industry says, even in the Taylor books. Though some of it is accurate, there's still a lot that's just hogwash.
Thanks for the info. Why would someone go though the trouble of manufacturing and marketing a product that is exceedingly expensive without there being some advantage? Marketing can only take a product so far if there aren't any tangible advantages. Who buys the stuff?
Lithium hypochlorite is the only solid form of chlorine that when added to a pool does not have the side effects of increasing CYA or CH. The following are chemical facts independent of product concentration or of pool size:
For every 10 ppm Free Chlorine (FC) added by Trichlor, it also increases Cyanuric Acid (CYA) by 6 ppm.
For every 10 ppm FC added by Dichlor, it also increases CYA by 9 ppm.
For every 10 ppm FC added by Cal-Hypo, it also increases Calcium Hardness (CH) by at least 7 ppm.
So if you don't want to increase CYA nor CH but of course need to add chlorine regularly, then lithium hypochlorite is the only solid source of chlorine that will do that. The solid form has a long shelf-life compared to chlorinating liquid that must be turned over regularly (bleach lasts longer due to its lower concentration of chlorine, but takes even more space as a result). At 35% Available Chlorine, it is nearly 3 times more compact than chlorinating liquid and 4-5 times more compact than bleach. So from a product storage and space requirement, lithium hypochlorite fits better into a stores' "profit per square foot" model (Cal-Hypo, Dichlor and Trichlor are even more compact, but are less expensive per FC and per volume).
Marketing goes a LONG way in pool stores as does deceit. Pool stores often do not tell people about the buildup of CYA using Trichlor pucks/tabs or that higher CYA levels make chlorine less effective so algae can grow unless you proportionally raise the FC level. Instead, they sell people higher-margin products such as algaecides, phosphate removers, clarifiers, flocculants, enzymes, "shock", etc. It's not all the pool stores' fault as they often just pass along what they are told from the manufacturers of those products. The lie that "CYA doesn't matter; only FC matters" has been told for nearly 40 years even though the science was definitively determined in this 1974 paper.
There are pool stores that provide the full array of products including chlorinating liquid. There is one in my area where I buy 12.5% chlorinating liquid that they store in the front of the store in the shade and they sell a lot of it, but they also have pyramid stacks of Trichlor buckets inside the store as well.
Good stuff! Thanks!