Three points after reading these posts

[smallpooldad]

Three points after reading these posts
Split off of this topic. JasonLion

First, should tenentwick not have added to tenentwick's 28,000 gallon pool for every 10 ppm of chlorine, 50 oz of Muriatic Acid or 5 oz for every 1 ppm chlorine to offset the effects of the chlorine, if the pH has risen would not the chlorine would be less effective? Would tenentwick be able to read the pH, even with a good test kit, at these high chlorine levels; unless of course he has a pH meter? The cloudiness might disappear faster.

Second, I realize that according to posts that the SWG can handle 3900 ppm of salt, but that does not mean it is good for the SWG. Once he turns it back on would it not run too hot thereby shortening the life of it? It is possible that if his Salt level was too high in the first place his cell may already be on the decline and would need a much higher than standard setting to offset the lowered production by a dying cell. This is maybe why he had this issue arise, he may need to replace the cell once this is over. Would it not be better to drain down a little now as he/she will have to do it eventually? This to would remove some of the cloudiness.

Lastly, was any nitrate test done, with a cheap aquarium test, to see if he his fighting an ongoing chlorine versus nitrate issue? Of course chlorine can control it but it would require more than normal amounts of chlorine to offset the ever present danger of potential algae blooms or growth. High levels of phosphates, if nitrates are present, increase the likeliness of this issue, phosphates can be an issue if high levels of nitrates are present. Unfortunately the only way to get rid of nitrates is to drain. One should reduce the nitrates to a manageable level if too high. Phosphates levels then are not that important if the nitrate is reduced, and would not normally require treatment.

 

[JasonLion]

Adding acid would be a very bad idea. Chlorine is long term PH neutral. The PH goes up when you add it, and then back down as the chlorine gets consumed. If you added all that acid the PH would end up extremely low.

Nearly all modern SWGs are designed to run within a range of salt levels. Within that range they are just fine, and outside of that range they shutdown automatically. Even if the cell was failing, it would not have caused the issues that have been seen.

Neither nitrate not phosphates will cause any of the issues you ascribe to them.

 

[chem geek]

Lastly, was any nitrate test done, with a cheap aquarium test, to see if he his fighting an ongoing chlorine versus nitrate issue? Of course chlorine can control it but it would require more than normal amounts of chlorine to offset the ever present danger of potential algae blooms or growth. High levels of phosphates, if nitrates are present, increase the likeliness of this issue, phosphates can be an issue if high levels of nitrates are present. Unfortunately the only way to get rid of nitrates is to drain. One should reduce the nitrates to a manageable level if too high. Phosphates levels then are not that important if the nitrate is reduced, and would not normally require treatment.

Algae are limited in their rate of growth by sunlight and temperature even if they had all the nitrates and phosphates they could possibly consume. Even under ideal conditions, they only double in population in around 3 hours. So sufficient chlorine levels relative to CYA will kill the algae before they can reproduce so that is why we say that the nitrate and phosphate or any other nutrient levels are irrelevant. Phosphates and nitrates do not directly react with chlorine -- the only chlorine demand comes from algae (or bacteria) growth when the chlorine level is insufficient to kill algae fast enough.

Richard320 recently wrote in this post, "Phosphates are food for algae. Wood is food for a fire. If you don't have a fire, it just sits there, same as your phosphates in the absence of algae." I think that's an outstanding analogy. If the chlorine is at sufficient levels to kill algae quickly, then there is no "fire" (i.e. algae growth) so the wood (i.e. phosphates and nitrates) don't do anything and are irrelevant.

You wrote about your getting algae just below the surface in your suction pool canister when your phosphates and nitrates were high and you wondered about lowering nitrates in this thread and in this post, but the fact you are only getting algae in that one place is most likely an indicator that the chlorine level is lower there for some reason than in the rest of the pool (or was lower there at some point and then biofilm formed). I don't know whether this is due to the type of water contact against the surface or flow rates or what, but most pools don't seem to have that problem -- when they get algae, it's most often in the main pool area. Also note that you hadn't had problems with algae until recently, but never checked the phosphate nor nitrate levels before yet you now assume that this is the reason for the problem when it might be something else in the water and by replacing the water you are removing whatever else was in it as well. Or perhaps the chlorine level got too low at some point and then biofilm formed making the algae stuck to that surface more resistant and possibly could have been vigorously brushed off and rubbed with concentrated chlorine (Trichlor puck, for example). So yes, reducing one or more of the algae nutrients in the pool will slow down algae growth even in areas where the chlorine level is too low, but that's not the first thing to do. If you look at how many thousands upon thousands of pool owners (here and on other forums) are able to prevent algae growth using chlorine alone regardless of nitrate or phosphate levels, I think you would agree that checking for nitrates and phosphates should not be the first thing to look for unless one doesn't mind at all the inconvenience or cost of removing phosphates and/or replacing their water to lower nitrates. It is one tool in the arsenal, but rarely a necessary one.