Well I already backedwashed. After I got done my psi was slightly over 20. How did that happen? I thought that it was supposed to decrease after backwashing.
Because the addition of a hypochlorite source of chlorine (chlorinating liquid, bleach, Cal-Hypo, lithium hypochlorite) raises the pH. When the chlorine gets consumed/used, this is acidic and lowers the pH so that when the FC comes back down you end up about where you started though in practice usually a little higher due to the excess lye in the chlorine and from some carbon dioxide outgassing that can occur in the interim. The initial lower pH is so that when you are at shock level the pH isn't too high.dbabz31 said:To chemgeek,
I am a little confused on your earlier post when I read through them. You said that overtime, as chlorine is consumed, that it is acidic, and causes PH to drop also. Why then for the low PH prior to shocking?