There have been some indications that sulfates might have a negative impact on plaster pools but the jury is still out. However, commercial pools that use sulfuric acid instead of muriatic (since it is non fuming) do tend to see more plaster damage that cannot be easily attributed to improper pH or calcium levels. Also, sulfates can foul some SWG cell designs leading to early cell failure.
Monopersulfate question.
- Thread starter seilsel
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But, it did have one advantage over liquid chlorine, in one case for me. It eliminated the black algae from my steps. I was able to dump a pretty heavy concentration on the steps, and let it disolve somewhat slowly. Bleach dispersed too quickly to be effective, without raising the level in the whole pool for an extended period of time = shock treatment for the whole pool. And, I don't know if that works to eliminate black algae. Does it? but that may be for a different topic.
So the potassium stays in the water, and the sulfates stay in the water, so do they continue to help fight algae while present?
So the potassium stays in the water, and the sulfates stay in the water, so do they continue to help fight algae while present?
The potassium sulfate does nothing with respect to algae. It's basically like salt except the sulfates at higher levels can have different negative effects than chlorides (but we don't know the specific levels when this is a problem -- waterbear commented on this elsewhere with regard to SWG cell).
It's not the MPS itself that was particularly useful against black algae, but rather that you could concentrate an oxidizer in one place. Cal-Hypo would have had a similar effect as would a Trichlor tablet, the latter being a very common approach, at least for plaster pools where you don't have the risk of bleaching or thinning a vinyl liner.
In the future, I'd just rub a Trichlor puck/tab over a black algae area. The key to killing black algae is frequently scraping off their "heads" exposing deeper levels to high chlorine levels. One can just shock with chlorine and frequently scrape the black algae surface, but using Trichlor can be faster -- but with the possible side effect of leaving a light mark in the plaster (like a local acid wash). In any event, if you've already got MPS, you can certainly use it for any oxidizing purpose.
Black algae doesn't form in pools that have properly maintained chlorine levels relative to CYA. It grows slowly so is an indicator of a long-term low FC/CYA ratio, usually due to high CYA level from continued use of Trichlor pucks/tabs.
It's not the MPS itself that was particularly useful against black algae, but rather that you could concentrate an oxidizer in one place. Cal-Hypo would have had a similar effect as would a Trichlor tablet, the latter being a very common approach, at least for plaster pools where you don't have the risk of bleaching or thinning a vinyl liner.
In the future, I'd just rub a Trichlor puck/tab over a black algae area. The key to killing black algae is frequently scraping off their "heads" exposing deeper levels to high chlorine levels. One can just shock with chlorine and frequently scrape the black algae surface, but using Trichlor can be faster -- but with the possible side effect of leaving a light mark in the plaster (like a local acid wash). In any event, if you've already got MPS, you can certainly use it for any oxidizing purpose.
Black algae doesn't form in pools that have properly maintained chlorine levels relative to CYA. It grows slowly so is an indicator of a long-term low FC/CYA ratio, usually due to high CYA level from continued use of Trichlor pucks/tabs.
In a word, no. The oxygen is gone from the chemical leaving only the sulfates and potassium. It's like the difference between sodium hypochlorite (chlorine bleach)and sodium and choride ions. Once the oxygen is gone there is noChasville said:
'killing power' left.
OR from very low FC levels because one is depending on copper, silver, and ozone to keep the water in shape (which it will not). Enough copper will keep black algae at bay but if you have enough copper to kill algae (including easily killed green algae) you have enough copper to stain the pool and turn hair green so it's a losing proposition since it wll sooner or later!chem geek said:
new to this.I maintain a 150,000 pool and 2 spas( 3300,6300)I used to use mps to raise the orp when the fc was 3-5 but orp at <600.it raises the tc and throws the cc out of whack but the alternative 8-10 fc and 600-650 orp as recommended by Poolcomm(the 600-650)Since we had to replace the 2 spa heaters,I stopped using mps and lowered the orp to 550 which keeps the fc in range.this has been a learning curve even to the pool builder service tech.any suggestions?
Welcome to TFP! 
Using MPS to raise the ORP is not the thing to do since the ORP is supposed to help you figure out the proper sanitation level and MPS does not sanitize as well as chlorine even though it does contribute to ORP because it is an oxidizer. You really should be more focused on the FC/CYA ratio rather than the ORP level. ORP should be used for process control to maintain a certain FC level but not as an absolute standard.
What is your source of chlorine? Are you using a saltwater chlorine generator (SWG) or a Trichlor inline chlorinator or dosing with chlorinating liquid? Is the pool outdoors exposed to direct sunlight (and how about the spas)?
You say the FC is 3-5 ppm, but what is the Cyanuric Acid (CYA aka stabilizer or conditioner) level? In spite of what you may have been told, ORP is not an absolute level and you get different readings on the same water from different sensor manufacturers. At a pH of 7.5 and 80F temperature, you get roughly a 791 to 812 mV ORP reading from an Oakton sensor and a 803 to 820 mV ORP reading from a Chemtrol sensor.
If your pool has 30 ppm CYA in it, then the 3-5 ppm FC would be around 647 to 672 mV on the Oakton and 689 to 709 mV on the Chemtrol. If you had 80 ppm CYA in the pool, then the 3-5 ppm FC would be around 604 to 626 mV on the Oakton and 655 to 672 mV on the Chemtrol. So your reading below 600 and at around 550 mV seems very strange unless your CYA level is extraordinarily high or the sensor isn't properly calibrated or is just an inferior sensor.
If I were you, I would just manage the FC/CYA level which in a commercial public pool should probably have an FC of around 20% of the CYA level so 6 ppm FC with 30 ppm CYA or 4 ppm FC with 20 ppm CYA. If you don't have any CYA in the water at all, then the chlorine will be quite strong and possibly accounts for your heater damage. You don't want very much CYA in the water, but with none at all then you'll want the FC to be much lower and that can be impractical to manage (such as the German DIN 19643 standard of 0.3 to 0.6 ppm FC with no CYA). You also don't want too high a CYA level because the ORP sensor won't work well at too low an ORP reading -- which already sounds like an issue for your unit as it is reporting quite low (though sounds like it still functions at being able to maintain FC levels).
Richard
Using MPS to raise the ORP is not the thing to do since the ORP is supposed to help you figure out the proper sanitation level and MPS does not sanitize as well as chlorine even though it does contribute to ORP because it is an oxidizer. You really should be more focused on the FC/CYA ratio rather than the ORP level. ORP should be used for process control to maintain a certain FC level but not as an absolute standard.
What is your source of chlorine? Are you using a saltwater chlorine generator (SWG) or a Trichlor inline chlorinator or dosing with chlorinating liquid? Is the pool outdoors exposed to direct sunlight (and how about the spas)?
You say the FC is 3-5 ppm, but what is the Cyanuric Acid (CYA aka stabilizer or conditioner) level? In spite of what you may have been told, ORP is not an absolute level and you get different readings on the same water from different sensor manufacturers. At a pH of 7.5 and 80F temperature, you get roughly a 791 to 812 mV ORP reading from an Oakton sensor and a 803 to 820 mV ORP reading from a Chemtrol sensor.
If your pool has 30 ppm CYA in it, then the 3-5 ppm FC would be around 647 to 672 mV on the Oakton and 689 to 709 mV on the Chemtrol. If you had 80 ppm CYA in the pool, then the 3-5 ppm FC would be around 604 to 626 mV on the Oakton and 655 to 672 mV on the Chemtrol. So your reading below 600 and at around 550 mV seems very strange unless your CYA level is extraordinarily high or the sensor isn't properly calibrated or is just an inferior sensor.
If I were you, I would just manage the FC/CYA level which in a commercial public pool should probably have an FC of around 20% of the CYA level so 6 ppm FC with 30 ppm CYA or 4 ppm FC with 20 ppm CYA. If you don't have any CYA in the water at all, then the chlorine will be quite strong and possibly accounts for your heater damage. You don't want very much CYA in the water, but with none at all then you'll want the FC to be much lower and that can be impractical to manage (such as the German DIN 19643 standard of 0.3 to 0.6 ppm FC with no CYA). You also don't want too high a CYA level because the ORP sensor won't work well at too low an ORP reading -- which already sounds like an issue for your unit as it is reporting quite low (though sounds like it still functions at being able to maintain FC levels).
Richard
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