Various metals in pool water should not be lumped together in how they react in pool water conditions. The following is my limited understanding regarding metals in pool water, and would welcome comments with different information.
I agree that copper is less soluble at a higher pH than at a lower pH, and therefore, will precipitate out some copper as the pH rises and solubility lowers. However, I do not believe there is a major solubility difference between a pH of 7.4 and 7.8 in terms of how much dissolved copper will precipitate out. My concern is that at a lower pH, it is more likely that copper will be dissolved from a heat exchanger and place copper into solution, thereby increasing it.
I do not believe that adding chlorine causes copper to precipitate out (as long as the pH remains the same). In fact, I believe that high chlorine residuals actually makes copper slightly more soluble.
If the copper content is well below its' solubility, raising the pH may not cause any precipitation of copper.
I suggest that "Iron" behaves much differently as compared to copper. Any dose of chlorine will begin to cause dissolved iron in water to become oxidized and precipitate out. In fact, iron will also become oxidized and precipitate out due to oxygen in the water, whether or not chlorine is added, and regardless of the pH (within reason). A high or low pH (in normal pool pH water conditions) does not play a significant role in how it reacts to chlorine and oxygen in water.
I believe that manganese and cobalt behave similar to iron, and silver and zinc behave similar to copper.
Generally, there are usually pros and cons to everything. Sometimes, one just has to decide what their priorities are. For me, I weighed the above and have decided that I prefer a slightly higher pH than what the pool industry's ideal of 7.4 to 7.6 suggests. Even though copper is less soluble at a higher pH, it is therefore less likely to be dissolved from copper heat exchangers.
As far as adding sequestrants, if there are no metals in the pool water or fill water, I see them mostly as not needed. If there is iron or copper in the fill water or pool water, then adding them can beneficial, but will need periodic additions because they may break down in chlorinated water and stop working. For start-ups especially, adding a sequestrant makes sense. Much of the iron in well or tap water can be oxidized by chlorine and get filtered out before it stains pool surfaces.
I agree that copper is less soluble at a higher pH than at a lower pH, and therefore, will precipitate out some copper as the pH rises and solubility lowers. However, I do not believe there is a major solubility difference between a pH of 7.4 and 7.8 in terms of how much dissolved copper will precipitate out. My concern is that at a lower pH, it is more likely that copper will be dissolved from a heat exchanger and place copper into solution, thereby increasing it.
I do not believe that adding chlorine causes copper to precipitate out (as long as the pH remains the same). In fact, I believe that high chlorine residuals actually makes copper slightly more soluble.
If the copper content is well below its' solubility, raising the pH may not cause any precipitation of copper.
I suggest that "Iron" behaves much differently as compared to copper. Any dose of chlorine will begin to cause dissolved iron in water to become oxidized and precipitate out. In fact, iron will also become oxidized and precipitate out due to oxygen in the water, whether or not chlorine is added, and regardless of the pH (within reason). A high or low pH (in normal pool pH water conditions) does not play a significant role in how it reacts to chlorine and oxygen in water.
I believe that manganese and cobalt behave similar to iron, and silver and zinc behave similar to copper.
Generally, there are usually pros and cons to everything. Sometimes, one just has to decide what their priorities are. For me, I weighed the above and have decided that I prefer a slightly higher pH than what the pool industry's ideal of 7.4 to 7.6 suggests. Even though copper is less soluble at a higher pH, it is therefore less likely to be dissolved from copper heat exchangers.
As far as adding sequestrants, if there are no metals in the pool water or fill water, I see them mostly as not needed. If there is iron or copper in the fill water or pool water, then adding them can beneficial, but will need periodic additions because they may break down in chlorinated water and stop working. For start-ups especially, adding a sequestrant makes sense. Much of the iron in well or tap water can be oxidized by chlorine and get filtered out before it stains pool surfaces.