Metal Sesquesterant and FC Level

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LadywithIron

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Jun 26, 2007
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Am I correct in thinking that adding Metal Sesquesterant before testing can cause FC levels to skyrocket? HEDP based? I am assuming that I let the Metal Sesquesterant 'wear out' because I have not added more water to the pool and this AM I had the Iron staining coming back, the filter was orange again, so I put in 1/2 quart of hth Metal Control. It is already clearing the water and I will vacuum shortly, but from my own experiments today it seems that the Metal Control is throwing off the Chlorine levels. If I am correct in this, how long should it take before I can get an accurate FC reading?


My test results from this AM are
FC 30 (definately 30)
CC 0 (this has been .5 for 2 weeks until now)
CYA 50 (This is up from 35)
PH 7.2 (all week steady)
TA 70 (all week steady)



I am also a little confused about how the sesquesterant works. Say there are tiny particles of rust floating around, does the sesquesterant resuspend those particles? Or is it the case that once they are out, they are just in the water and stay there unless removed by the filtering?

16X48 Intex
6000 Gallons
2000GPH Intex Pump Larger Filter
Hayward Aqua Critter Vac
 
Adding metal sequesterant doesn't usually effect chlorine, though some of them seem to consume some chlorine.

The sequesterant binds to the metal ions and keeps them from depositing as stains. The metals are still in your water, and will still test as present, just held so that they stay harmless. In some cases the sequestered metals can clump together and get filtered out, but this seems to be quite rare.

Sequesterant breaks down slowly, releasing the metals back into the water, so you normally have to add maintinace doses weekly.
 
There is something wrong with my FAS/DPD test apparently. I am using level small scoops, or as level as I can get and following directions. Today is the first time that I have used it. I just assumed that it was correct.

This evening with it, I am getting
14ppm FC
O CC

With the Taylor K 2005
1.5 pm FC
.5 CC

With the Hth Test from Walmart
TC 2.ppm


There just isn't any possible way that I had a real FC reading of 30ppm because I have not had that kind of chlorine in the pool at once, I only add 12 oz at a time as to not cause staining. Yesterday with the sun shining, I only added 24 oz, 12 at each adding.
 
On the FAS-DPD test you don't need to measure the powder acurately, just put in enough so you get an obvious pink color, typically one or two scoops.

Are you using the 10 mL sample size and counting 28 drops till the water turns clear? If you more or less filled the test cylnder I would expect you to need about 28 drops if FC was really a little below 1.5.

The reagents can go bad, but that normally takes years. There have also been some defective droppers in the past, but they never caused errors nearly this large.
 
Well, this afternoon, I used the 25ml line, put in two scoops, of R-0870 powder, and it took 7 drops of the R-0871 to get the Pink to go away. So I multiplied that by 2. That was how I got the 14ppm. After 5 drops of R-0003, the water stayed clear.

Early this AM, it took 15 drops of R-0871 to get the pink to go away, this was also with the 25ml, so I multiplied that by 2, and then I refilled to 10ml and it took 6 drops of the R-0871 to get the pink to go away, so I multiplied that x 5. At no time did I get any color back after adding the 5 drops of R-0003.

Am I doing this correctly?


For tonight, I think I will go ahead and raise the chlorine to 3ppm. Slowly. So if the other 2 test are correct and the FAS/DPD test is incorrect I will have the minimum atleast overnight. And if the FAS/DPD is correct, I still won't be too far past the Max.

I have a smaller pool to fill, and I may be able to do that tomorrow, and starting from 0 see which tests are correct I guess.

Thank you very much for your help:)
 
With a 25 mL sample you divide by 5 (the same thing as multiplying by 0.2). Another way to do it is to multiply by 2 and then move the decimal point one to the left. So your FAS-DPD test is telling you the FC level is 1.4, which is consistant with the other tests.
 
Thank you Ric, and Jason:) I appreciate the heads up, and knowing what is going on and all, and I can stop suspecting the neighbor of secretly shocking my pool during the night, man I feel like such a twit! :oops:

So this is all right in line, just a tiny bit lower than what the other two tests were showing.

Don't worry, no one is letting me handle any of the accounting around here. :) I do not work for the government or anything....
 
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