Testing Iron with Taylor K-1716 Kit and Sequestrant in Pool

[smallpooldad]

Assuming the folllowing parameters:

pH 7.3
Jack's Magic Purple Stuff maintained at 20 ppm (using sequestrant test kit twice per week)
Jack's Magic Magenta Stuff added at a rate of 5 oz once per week

If I tested for iron with the Taylor K-1716 Kit Iron Test Kit, which uses reagents R-0851 and R-0852, would a low pH of 7.3 and the use of sequestrants bind the iron, or keep it in solution, so that despite there still being some iron in the water show a reading of 0 (zero) ppm, or if iron is present will it still be able to show that.

My guess is that it will show zero ppm but I am not sure.

Any help would be appreciated.

Thank you.

 

[JamesW]

Re: Testing Iron with Taylor K-1716 Kit and Sequestrant in P

Polyphosphate sequestrants can cause interference.

High copper, nitrite, molybdate, and polyphosphate levels may cause interference.

http://www.taylortechnologies.com/produ ... KitID=2200

 

[smallpooldad]

Re: Testing Iron with Taylor K-1716 Kit and Sequestrant in P

JamesW,

Thank you for your very fast reply.

Aloha

 

[smallpooldad]

Re: Testing Iron with Taylor K-1716 Kit and Sequestrant in P

JamesW,

Tested for Phosphates which you correctly pointed out are are in sequestrants. The level at which I stopped testing was way in excess of 5,000 ppm! I am pretty sure you are correct that this Phophates level would invalidate the Taylor's Iron Test Kit results.

FC is around 5, there are absolutely no algae problems nor does the pool have any iron stains or calcium scaling. In fact since keeping the pH at 7.3, adding the two sequestrants from Jack's, and keeping the calcium at around 300 ppm the pool has never looked better since it was first built 16+ years ago.

So again it goes to prove that even very high levels of (inorganic - see below) phosphates seem to have absolutely no negative effects if the FC is maintained properly. I will test again but my guess is they are in the 7,500 to 10,000 range.

If I remember clearly, and I might not, this type of inorganic phosphate is a salt of Phosphoric acid and is different somewhat from organic phosphate which is an ester of Phosphoric acid, but cannot be tested for separately in the standard pool shop Phosphate test kits. I think I am correct about the issue of testing. I am not sure if there is a level beyond which organic Phosphates might cause a problem, but how to test?

Now I wonder how many poor pool owners have added Phosphate based sequestrants and then told their phosphate levels are too high and needlessly been sold Phosphate Remover.

Thank you for your help and making me think this through.

 

[chem geek]

Re: Testing Iron with Taylor K-1716 Kit and Sequestrant in P

Polyphosphate is the form of phosphate cells typically store for future use. So it is an available form of phosphate for algae, though not quite as rapidly useful as orthophosphate. Nevertheless, it's still more useful than organic phosphates that algae only take up relatively slowly. If the chlorine level gets to zero, however, then bacteria can fairly rapidly convert organic phosphates to orthophosphate at which point algae can grow rapidly.

As for lanthanum-based phosphate removers, lanthanum precipitates orthophosphate readily, but does not do so with polyphosphate as readily and if carbonates are present, which they are in pools, then lanthanum carbonate is formed rather than lanthanum polyphosphate. That is, in terms of solubility from least to most we have:

lanthanum phosphate < lanthanum carbonate < lanthanum tripolyphosphate

So we can add polyphosphate to the list of what standard phosphate removers do not remove well, though some contain clarifiers that seem to help with their removal (they may help to coagulate the lanthanum tripolyphosphate ion pairs). And yes, the fact that you've got lots of polyphosphate in the water but don't have algae growth does show that phosphates don't matter if you have a higher FC level, but the real test is with orthophosphate.

 

[smallpooldad]

Re: Testing Iron with Taylor K-1716 Kit and Sequestrant in P

Chem Geek,

Thank you for the post that reply was "Awesome" as my daughter and grandchildren would say. And even better it was very clear.

So if I am understanding you correctly, that a well balanced CyA of 70 to 80 ppm and FC with around 5 should offset any potential growth of algae for a good deal of time. At some point these inorganic phosphates might be converted to such an extent that even a properly balanced CyA and FC might not be able to cope.

Two Questions:

So if I were to do an in-pool AA treatment in a year or so I might get in trouble if I dropped the chlorine to zero, then the algae might have a field day very quickly by dining on the built up reservoir of orthophosphate. Is that a correct assumption?>

My solution to this in my 10,000 gallon pool might be to drop 2 quarts of Algaecide 60 in the pool 6 hours before the treatment, do you think that might work/help?

On the plus side I am getting no iron staining that I can see using my current method. Usually without the new procedure of blending two sequestrants and the increase to a higher maintance level of 20 ppm of the Purple Stuff I would already start to see some faint staining. So the time might come when algae growth occurs before staining, which leaves me with option of either draining or upping the FC level, as the cost of the Phosphate removal would be even more expensive than a drain and refill.

Thank you for your help.

 

[JasonLion]

Re: Testing Iron with Taylor K-1716 Kit and Sequestrant in P

If you do an AA treatment you should use algaecide, and if you do, and don't make any large mistakes, everything will be fine. Even if you don't use algaecide, your odds of doing an AA treatment without getting algae are fairly good (though hardly perfect) regardless of the phosphate level.

 

[smallpooldad]

Re: Testing Iron with Taylor K-1716 Kit and Sequestrant in P

JasonLion,

Thank you for the quick reply.

I do use Algaecide 60 when I do the AA treatment, so hopefully all will be well, and hopefully I will not have to do it for a long, long time, time will only tell.

Thank you.

 

[chem geek]

Re: Testing Iron with Taylor K-1716 Kit and Sequestrant in P

At some point these inorganic phosphates might be converted to such an extent that even a properly balanced CyA and FC might not be able to cope.

I wouldn't put it that way. The recommended FC/CYA levels on this forum are such that they should prevent green (and black) algae growth regardless of phosphate level. Basically, the algae growth is limited by sunlight and (optimum) temperature. At least it seems that way given the many thousands of pools not getting algae at recommended levels independent of phosphate level. There is a failure rate of around 1 in 5000 or so (best guess) but it doesn't seem to be related to phosphates and may be more about circulation or test interference leading one to the wrong actual levels or other (rare) chemicals that may act like CYA binding to chlorine but are not measured or something else we don't yet understand.

 

[smallpooldad]

Re: Testing Iron with Taylor K-1716 Kit and Sequestrant in P

Chem Geek ,

Thank you that makes it very clear.

Aloha