In-Pool AA Iron Treatment with Very Very High Phospates

[smallpooldad]

I am planning on doing this treatment sometime before Xmas, my only concern is the very high phospate level due to the use of Jack's Purple Stuff.

I was also planning on adding 16oz of Algaecide 60, the day before as added insurance, but bring the Chlorine back to 3 ppm on that day.

I will put the AA in the pool after dark, about 7 pm and adding back Chlorine as need prior to sunrise at about 5:30 am the next morning

With phosphates levels being in all probabilty way in excess of 30,000 ppb will I get an algae bloom or excessive ammonia build-up and have to use large amounts of chlorine to combat the effect of the very high phospate levels? Or would it just be better to drain once treated? In other words the cost of treating the pool with Algaecide 60 - $34 in Hawaii per 32 oz and large amounts of chlorine and time spent treating to compensate might work out the same as a drain.

For information: Water temps are around 68F and the pool stays in the shade till noon.

Thank you to those of you that might help.

 

[PJ]

What are your current readings?

 

[chem geek]

Even with the highest phosphate and nitrate levels, algae growth rates are still limited by sunlight and temperature. That's how chlorine alone can keep algae from growing in spite of such high nutrient levels. Now with your lowering the chlorine level to zero for the ascorbic acid treatment, you can help prevent algae growth by using an algaecide such as Polyquat 60. By using the algaecide and doing the AA treatment at night, you should be able to minimize algae growth (if your pool water temperature is cooler, that also helps slow down algae growth).

Algae takes around 3 to 8 hours to double in population so there will be relatively little growth overnight or even after one day. Whenever people see visible algae, it was actually there growing for at least a day or two, but not yet visible. If you do find some growth or some unusually high chlorine demand, you can bring up the chlorine level if needed. Of course, you don't want to raise the chlorine level too quickly or else you can raise the pH and/or break down the sequestrant and cause staining again. I think you'll do fine, however.

 

[smallpooldad]

PJ,

Good question I should have posted them.

These are the numbers at 68 F:

FC 4
pH 7.4
TA 80
CH 370
CyA 70
Salt 3200
Borates (zero-dog)
CSI -0.47

Chem Geek,

Thank you for the reply and the very helpful and clear advice. I will do an in-pool AA treatment based on your analysis. I realize that this does not guarantee that all will go well but I would prefer not to drain if possible. I will also buy some extra sequestrant.

I will let you know how it goes. I will try and do it sometime in the next seven days.

Happy holidays to you both.