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...The 2 reasons you bought your tub, i.e. hot water and jets, are the two biggest culprits of causing your water balance to change. The hotter the water is, the more your pH will want to rise on its own, and as air is induced into your tub via your jets, your T.A. will slowly lower over time. You shouldn't need any pH increaser unless you are not maintaining your water on a weekly/bi-weekly basis. The only reason you would ever need pH increaser is if you allow your T.A. to fall too low. (T.A. is a pH buffer)...
Tubsandcues, I've seen you mention heat as a cause of pH-rise a couple of times and wondered if you would explain that a little more.My understanding of pH is that it is a measure of the relative balance between acidic and basic compounds in a solution. I don't see how heat would affect it unless the water is hot enough to evaporate the base or acid (the H2O is neutral).I understand your comments regarding TA as a pH buffer and air as an agent that lowers TA (I believe pH as well), but FYI -- my pH tends to drift down over time in spite of TA on the upper end of normal. This is with a dichlor system, and little/no MPS. I monitor my water regularly, but I do have a need for soda ash/baking soda, and would be surprised if others don't as well, especially MPS and bromine users.
From BioGuard 2000 ChemPlus manual, pg. 225:"The heat also causes carbon dioxide to become less soluble in water forcing it to gas off. In addition to the heat, aeration and venturi air injection also eliminate carbon dioxide. Without CO2 in the water, carbonic acid is unable to form and the pH tends to rise causing cloudiness, scale formatoin, inefficient sanitizer activity, and bather discomfort."
TubsAndCues,Here's my current plan, my tub is 400 gallons.Use Nature 2. Shock with 1/2 teaspon Dichloro after useSundayClean filter and shock with 1 1/2 teaspoons Dichloro WednesdayAdd Stain and Scale inhibitorHow does this sound?Thanks for your help,Mark
Notice at the bottom: 1 Tablespoon MPS = 3 Teaspoons Dichloro
1 Tablespoon MPS = 3 Teaspoons Dichloro