What is the difference in using 47.6% calcium hypochlorite in my spa vs the 56% stuff?

Use the 56. I really don't know why, but I've always heard the Hypochlorite is bad. I know the 56 is almost pH neutral.

56% is 17.64% stronger (higher concentrated) than the 47.6% stuff " title="Cool" /> Buy the one which is less expensive/concentration. (I know lots of Pool/Spa stores will want to sell you the more expensive stuff. Went in one of those stores and it's just amazing what the sales people try to sell the consumers " title="Laughing" /> ) Of course you would be better off (for example) buying 47.6% calcium hypochlorite at (again - for example) 2 $ / unit as compared to buying 56% at 2.80 $ / unit. Concerning Calcium Hypochlorite with 56% being "pH- neutral ": Even if it was, it wouldn't really change anything in your tub, considering the tiny quantities required (perhaps 1 Teaspoon /day ?)

I just prefer to use a product that is not acidic.

Whenever you add chlorine granulars into your tub your pH will go up. If there was such a thing (calcium hypochlorite - commonly refered to as "chlorine granulars", which would be slightly acidic or neutral - I'd be the first one to use it. " title="Cool" /> The only way to add chlorine into your Pool/Tub without raising the pH would be chlorine gas (Chlorine in its purest form). This actually would bring your pH down

I guess I've been mislead for years. I've been fixing spas since 1987 and have always been told that chlorine granules are slightly acidic. I have never heard of anyone saying chlorine granules raise pH until now.

You see - it's never too late to learn " title="Cool" />

Dichlor is a 7 on the pH scale.
Hypochlorite is an 11.
Were you thinking of Hypochlorite?

Yes- that's what we have been talking all along

OK - thanks. I always thought Dichlor could lower pH.
I appreciate it.

Dichlor will lower your pH. "Dichlor" as such is mainly used in certain Chlorine pucks, which in turn will lower your pH. Now : Those chlorine pucks which contain Dichlor have this "stabilizer" ingredient (acidic). What happens now is that the amount of stabilizer ( which is to protect the destruction of Chlorine by UV Rays -such as the Sun) in your water will slowly creep up. This will also reduce the effectifiness of the Chlorine " title="Crying or Very sad" /> The only way to reduce your Stabilizer amount in your tub is by diluting the water (fresh water). 40 ppm are acceptable, but more than that is not a good thing to have. In other words : 3ppm of FAC (free available chlorine) will be efficient to sanitize your water and keep it germ free (if you got 0 Stabilizer in your water and if your FAC equals your total Chlorine) If - on the other hand - you got 60 ppm Stabilizer ( Cyanuric Acid ) in the tub, you would have to have (probably) 5ppm of FAC in order to achieve the same " killing power" of Chlorine. The only way to see whether your water / chlorine content is doing its job is to measure the ORP (Oxidation Reduction Potential) in your Pool / Spa. If the value is >700 mV your water is safe and no bacteria/germs will survive. Obviously the aim is to have low chlorine levels but still high ORP in your water. Chlorine is most effective at ( as far as I remember) a pH of 5-6. Of course this would cause corrosion in a Pool/Spa, and probably wouldn't be good for your skin either " title="Twisted Evil" /> Therefore you should keep your pH slightly in the base range (above 7) -. Example : FAC = 1ppm, pH=7.2 - your ORP should be around 720 FAC= 1ppm, pH = 8 - ORP probably around 600 mV (= very little sanitation)