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I do it a little differently. Because I use a minimal amount of dichlor after use, I like to get my free chlorine level to the 3-5 ppm level once per week. This would be about 1 tablespn dichlor for my 485 gallons of water. I shock with 2 tablespns unbuffered MPS when needed.By the phrase "when needed" do you mean when you want to soak right away? Other wise when do you know when to use MPS or Dichlor for shocking?Used or spent chlorine form chlorimines. This is what gives a chlorine spa or pool that "chlorine smell". This is measured by the difference between total chlorine and free chlorine and is called combined chlorine. Combined chlorine has very little value. When the combined chlorine level reaches .2 ppm, you must shock to oxidize or vaporize to purge them from your water. This can be done by quickly raising the free chlorine level to what is called breakpoint chlorination or by adding a sufficient amount of non chlorine shock. There are advantages and disadvantages to both. Shocking with chlorine will add to CYA levels and you cannot use the spa until the chlorine level drops, but you get the benefit of a superchlorination. Non chlorine shock has the advantage of use almost immediately after shocking, but will add to TDS. It is also more foolproof because if you don't add enough, it still oxidizes what it can..if you add too much, it stays until it can ozidize. With chlorine shock, if you don't add enough, shocking will not occur and you will have water with a high chlorine level and still have chlorimines. After shocking, your free chlorine levels should equal your total chlorine level.
'it's all still a mystery to me. When I shock with a high dosage of chlorine to to oxidize the chloramines, it sounds to me as if I'm just creating new chloramines?
Not without something to create them. Chloraminies are formed by the reaction of free chlorine with ammonia wastes from bathers. Shocking with chorine raises the chlorine level dramatically in a short period of time. When free chlorine measures ten time the combined chlorine level, breakpoint chlorination occiurs. Chloramines are oxidized (explode) and are released as a gas (why you keep your cover off). Its all just chemistry.