How does this chemical work?
-Disodium salt of ethylenediaminetetraacetic acid dihydrate
-Diammonium sulfate
-YELLOW OUT
-Disodium salt of ethylenediaminetetraacetic acid dihydrate
-Diammonium sulfate
-YELLOW OUT
Diammonium Sulfate, YELLOW OUT
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Others with more chemistry knowledge will give you a better answer, but the laymans' answer is, "Not very well. Don't use it."
Yes, and no. It will kill algae if used correctly, but we never recommend using it. The only time you might want to consider it is when CYA is way too high, there is algae, and lowering CYA is completely out of the question. It tends to create extreme chorine demand, and if not managed just right can create more problems than it solves.
Colloidal Silver
If the cyanuric acid is very high, and the owner refuses to drain and refill, is colloidal silver a good treatment for yellow algae?
If the cyanuric acid is very high, and the owner refuses to drain and refill, is colloidal silver a good treatment for yellow algae?
Diammonium Sulfate contains ammonia. When used properly the ammonia it contains creates large quantities of monochloramine. Monochloramine is an algaecide, and it is not affected by CYA.
Silver has exactly the same issues as copper, effective doses are right at the same level where staining is likely, and also like copper, silver stains are very difficult (and occasionally impossible) to remove. Silver also costs significantly more than copper.
Silver has exactly the same issues as copper, effective doses are right at the same level where staining is likely, and also like copper, silver stains are very difficult (and occasionally impossible) to remove. Silver also costs significantly more than copper.
The "Disodium salt of ethylenediaminetetraacetic acid dihydrate" is EDTA and while it's normally used as a metal sequestrant, it tends to break down from chlorine too quickly for us to recommend for that purpose and is why we recommend HEDP instead. EDTA is also an algaecide though not a very strong one (this EPA document indicates 50% kill of green algae over 96 hours when using 3 ppm EDTA).
Basically, the main purpose of using either an ammonium-based algaecide or a sodium bromide algaecide is to get around a high CYA level since chlorine will react with the former to produce monochloramine and the latter to produce bromine neither of which bind to CYA so both retain their full strength as an algaecide. Of course, this just hides the real problem which is a CYA level that is too high. So we generally recommend doing a partial drain/refill to lower the CYA level and then use the SLAM process to kill off the algae and then subsequently maintain the proper FC/CYA ratio as indicated in the Chlorine / CYA Chart to prevent algae growth.
Yellow/mustard algae is more resistant to chlorine so needs to be thoroughly eradicated unless one is willing to maintain an FC/CYA level that is roughly double that in the chart. This algae prefers shade (not complete dark, but avoids direct sunlight) so one must clean out light niches, get under removable ladders, and clean all equipment (poles, etc.) used in the pool.
Basically, the main purpose of using either an ammonium-based algaecide or a sodium bromide algaecide is to get around a high CYA level since chlorine will react with the former to produce monochloramine and the latter to produce bromine neither of which bind to CYA so both retain their full strength as an algaecide. Of course, this just hides the real problem which is a CYA level that is too high. So we generally recommend doing a partial drain/refill to lower the CYA level and then use the SLAM process to kill off the algae and then subsequently maintain the proper FC/CYA ratio as indicated in the Chlorine / CYA Chart to prevent algae growth.
Yellow/mustard algae is more resistant to chlorine so needs to be thoroughly eradicated unless one is willing to maintain an FC/CYA level that is roughly double that in the chart. This algae prefers shade (not complete dark, but avoids direct sunlight) so one must clean out light niches, get under removable ladders, and clean all equipment (poles, etc.) used in the pool.
The Yellow Out MSDS list Disodium salt of ethyenediaminetetraaceticaciddihydratediammoniumsulfate 100%. Is that one compound or two? (Disodium salt of EDTA and Diammonium sulfate). The MSDS does not have CAS number(s).
Welcome to TFP! 
It's really two chemicals when it dissolves in the water. In water it becomes EDTA and ammonia (mostly ammonium ion). The EDTA has some algicidal properties and the ammonia is used to combine with chlorine to form monochloramine which is somewhat effective against yellow/mustard algae, especially when the CYA level is high since monochloramine is not moderated in its strength by CYA. It's similar to using sodium bromide to from bromine to get around being moderated in strength by CYA. You'll see both such chemicals (ammonia and bromide) used in yellow/mustard algae products.
The Yellow Out product will consume chlorine with the ammonia combining with chlorine in seconds. If there is any leftover chlorine or if you add more chlorine later, it will oxidize the EDTA over days and you may notice that as additional chlorine demand until you get rid of all the EDTA in this fashion.
We recommend getting rid of yellow/mustard algae through super-chlorination and getting behind light niches and under removable ladders since yellow/mustard algae prefers shade, but if your CYA level is high then the first thing to do is to dilute the water (partial drain/refill) to lower it. Otherwise, the problem will come back again. See the Pool School article on Mustard Algae for more info.
It's really two chemicals when it dissolves in the water. In water it becomes EDTA and ammonia (mostly ammonium ion). The EDTA has some algicidal properties and the ammonia is used to combine with chlorine to form monochloramine which is somewhat effective against yellow/mustard algae, especially when the CYA level is high since monochloramine is not moderated in its strength by CYA. It's similar to using sodium bromide to from bromine to get around being moderated in strength by CYA. You'll see both such chemicals (ammonia and bromide) used in yellow/mustard algae products.
The Yellow Out product will consume chlorine with the ammonia combining with chlorine in seconds. If there is any leftover chlorine or if you add more chlorine later, it will oxidize the EDTA over days and you may notice that as additional chlorine demand until you get rid of all the EDTA in this fashion.
We recommend getting rid of yellow/mustard algae through super-chlorination and getting behind light niches and under removable ladders since yellow/mustard algae prefers shade, but if your CYA level is high then the first thing to do is to dilute the water (partial drain/refill) to lower it. Otherwise, the problem will come back again. See the Pool School article on Mustard Algae for more info.
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