Is this mustard algae?

[mcleod]

I would suggest you wait until you complete the OCLT tomorrow AM. If you pass that, that confirms to me there is no algae in your pool.

Report that FC test in the AM and sit tight for a bit.

Failed OLCT. Morning Test results:
FC 12 (last night FC 18)
TA 80
CYA 30
pH 7.4
Temp 73

 

[JoyfulNoise]

Ahhh! Thank you for the reply. Your response raises additional questions.
1) Would the outcome have been different had I used a sequestering agent after the AA treatment? Regardless of the sequence?
2) Is there a point where enough chlorine is added to the water to neutralize the AA? Would I have been able to determine that point from FC testing?

1. Use of a sequestering agent is necessary because the AA breaks down once you add chlorine and the iron will be oxidized. You add the sequestering agent once the stains are lifted to KEEP the iron in solution and prevent it from oxidizing. When iron is in the water, you have to raise the FC very slowly and only use the minimum amount or else the chlorine will oxidize the iron and cause the water to go brown/green.

2. Yes, you can see the effects of AA and chlorine as the FC will not hold until all of the AA is oxidized by it.

 

[duraleigh]

That FC loss means algae. As Joyfulnoise suggests, SLAM your pool. Use of polyfill in the skimmers can only help.

My knowledge of AA treatment is a bit limited.......Joyful is a true expert.

 

[mcleod]

1. Use of a sequestering agent is necessary because the AA breaks down once you add chlorine and the iron will be oxidized. You add the sequestering agent once the stains are lifted to KEEP the iron in solution and prevent it from oxidizing. When iron is in the water, you have to raise the FC very slowly and only use the minimum amount or else the chlorine will oxidize the iron and cause the water to go brown/green.

2. Yes, you can see the effects of AA and chlorine as the FC will not hold until all of the AA is oxidized by it.

I am ordering a metals test kit to determine metals in pool and source water. Can one remove iron from water when in a sequestered form?

 

[JoyfulNoise]

I am ordering a metals test kit to determine metals in pool and source water. Can one remove iron from water when in a sequestered form?

Not easily, no.

Metal testing is very complex and those kits tend to only give results for free iron that is in a soluble form. If iron is present as a suspended precipitate (oxidized) OR held in solution by a sequestering agent, the simple color comparison tests will not detect it. There are very complicated lab procedures for measuring metal levels when you have both free and precipitated iron.

You’d be much better off sending out a water sample to a reputable water testing lab and letting them do the analysis as they will use much more sophisticated techniques for determining the concentrations of metallic species in the water.

 

[mcleod]

Good Morning One and All
Did a OCLT over night.
Last night. FC 23. CC 0.5
This morning. FC 23. CC 0.5
The water appears to be clear, as in having clarity, but not the blue color one might expect. The color tends towards a slight bluish green. Could this be the result of the iron in the pool?
Is the SLAM over?
Sidebar question. Is there a way to determine how much FC loss a particular pool might have typically?
Mc

 

[JoyfulNoise]

I would say the SLAM is complete and you should start letting the FC come down on it own. The greenish hue could be from iron. If you have polyfill in the skimmer, I’d leave it in place until the FC return to normal and then see how the color looks and if there is any iron staining in the polyfill.

A clean and clear swimming pool with the proper FC/CYA ratio should lose anywhere from 2-4ppm FC per day and, theoretically, zero FC overnight. However, TFP considers an overnight loss of less than 1ppm to be ok.

 

[mcleod]

I would say the SLAM is complete and you should start letting the FC come down on it own. The greenish hue could be from iron. If you have polyfill in the skimmer, I’d leave it in place until the FC return to normal and then see how the color looks and if there is any iron staining in the polyfill.

A clean and clear swimming pool with the proper FC/CYA ratio should lose anywhere from 2-4ppm FC per day and, theoretically, zero FC overnight. However, TFP considers an overnight loss of less than 1ppm to be ok.

Polyfill? Like pillow stuffing? Too late for that now going forward?

 

[JoyfulNoise]

Polyfill? Like pillow stuffing? Too late for that now going forward?

Yes. Some people stuff a bit of it into the skimmer basket. The increased surface area tends to capture fine iron precipitates. It’s not at all necessary but can sometimes be helpful. Your sand filter may show signs of iron if the backwash water looks brownish/red colored.

Either way, just let the FC come down and see where everything settles.