Algaecide-affect readings?

[Thinkly]

I recently added perhaps to much ammonia based algaecide. Now my tf-100 kit appears to no longer take readings. I can not get a TA reading nor a chlorine reading. My ph seems to be lower than any color on the scale. Are these affects of the algaecide?

 

[Thinkly]

BTW, the water is crystal clear.

 

[chem geek]

Why are you using algaecide?

An ammonia-based algaecide will combine with chlorine to form monochloramine. If you added too much, then adding chlorine will simply form more monochloramine. You would measure zero Free Chlorine (FC), but should be measuring significant Combined Chlorine (CC). Is that what you are seeing?

As for the TA test, what exactly are you seeing? Instead of going from green to red, is the color going from blue to yellow? You should be able to use more drops of thiosulfate solution (R-0007) to neutralize the monochloramine if it is interfering with the dye in the TA test.

As for the pH, I don't know if monochloramine interferes with the test, but if it did it would likely have a similar effect as chlorine and tend to give falsely high readings. You are reporting lower readings (more yellow).

I think the thing to do is to shock with chlorine until you register FC and get the CC down. Again, why are you using algaecide instead of just shocking with chlorine?

 

[JamesW]

Is this what you're using?
n-Alkyl (60%C14, 30%C16, 5%C12, 5%C18) Dimethyl Benzyl Ammonium Chlorides-49.8%

Or, are you using something that contains ammonium sulfate or aqua ammonia?

Also, based on your previous readings, and what you have added, what is your best estimate of what all of the readings are?

 

[Thinkly]

Is this what you're using?
n-Alkyl (60%C14, 30%C16, 5%C12, 5%C18) Dimethyl Benzyl Ammonium Chlorides-49.8%

Or, are you using something that contains ammonium sulfate or aqua ammonia?

Also, based on your previous readings, and what you have added, what is your best estimate of what all of the readings are?

I am at work so can't list the ingredients in the algaecide. The primary problems I had when testing the water was when testing FC, the water NEVER changed to pink after adding 871 powder. When testing TA, the problem was when i added the R008 (green colored). The test vial went to a very dark purple, almost a black. After adding a countless # of R007 it never dropped back. (I believe I have these numbers correct-again I am at work.)

Essentially I have water with a lower pH reading than I have ever seen. The color was yellow. I also have water I can't get a viable test on for FC and TA. I also of course can't measure for combined chlorine because the water never turns pink after adding the 871 powder. It just stays clear.

As to why I added algaecide, it was because my pool got dirty from wind storms and the walls started to turn yellow. I shocked it very hard and it still wouldn't clear. So I added the algaecide and it turned crystal clear almost immediately. I now just have the issue of having water I can't test.

 

[chem geek]

I also of course can't measure for combined chlorine because the water never turns pink after adding the 871 powder. It just stays clear.

You don't have to have the sample turn pink for you to test CC. If you don't even see a flash of pink with the powder or you add extra powder to make sure (where clear means zero FC), then just add the 5 drops of R-0003 reagent at that point and if the sample turns pink/red, then you've got CC. I suspect that is what you will see.

As for the TA test, perhaps monochloramine causes the effect you are seeing.

As for pH, perhaps it is what happens when ammonium chloride reacts with chlorine:

NH₄⁺ + HOCl ---> NH₂Cl + H₂O + H⁺
Ammonium Ion + Hypochlorous Acid ---> Monochloramine + Water + Hydrogen Ion

though in practice with CYA in the water the following is probably what primarily occurs:

NH₄⁺ + HClCY^- ---> NH₂Cl + H₂CY^- + H⁺
Ammonium Ion + Chlorine bound to CYA (ion) ---> Monochloramine + Cyanurate Ion + Hydrogen Ion

I wonder if the yellowing of the walls came from the pH rising from the storm (perhaps aerating the water with rain/wind) and was really metal staining. Shocking would not have helped in that case and could make it worse due to increasing the pH even further. The algaecide itself probably didn't do anything directly, but the lowering of the pH redissolved the metal stains. That's my best guess at this point.

Anyway, try the CC test again as I described (i.e. don't wait for the pink if you don't see it and just proceed to adding R-0003). If that confirms you've got CC, then the solution is to add lots of chlorine to get rid of it.

 

[JasonLion]

My thinking is along the same lines as chem geek, but I am more worried about the PH. It really doesn't matter what the CC level is right now. If the PH is way low, it is much more important that you resolve that first.

Your description of what happened normally means that the FC level is zero, which seems very likely to me. Still, the FAS-DPD chlorine test can go wrong once in a long while. If at all possible you should try the simpler OTO chorine test. If the OTO test shows TC at zero, then there really isn't any chlorine in the pool (which again wouldn't surprise me at all).

What chemical did you use to "shock"? By the by, shocking the pool is a process, not something you do all at once and are then done with. From your description it doesn't really sound like you properly shocked the pool, though I can't be sure. See the article in Pool School to see how to shock the pool properly.

When the walls of the pool turn yellow, and the yellow does not brush off, then it isn't algae. Did you try brushing off the yellow? Yellow that doesn't brush off is very likely to be iron stains, which would have vanished if the PH went really low.

Regardless of everything above: If the PH test is reading below 7.0 the first thing you need to do is to raise the PH up to something more reasonable. That should be done soon.

 

[chem geek]

Not only is Jason making an excellent point, but getting rid of the monochloramine in the pool using chlorine is only going to lower the pH even further so as Jason says you really need to raise your pH level probably to something close to 7.5. You can then tackle getting rid of the monochloramine, if you determine that CC really exists.

 

[Thinkly]

Here are my current numbers:
FC .5
CC 5.5
TC .5
pH 6.8
TA 10
CYA 100+

So don't I need to fix TA before pH? Remember that I am skeptical of TA reading. It starts a dark purple and shifts to red with one drop.

 

[JamesW]

Are those numbers plausible? Based on your previous readings and what you have added, is the low TA and pH expected?

If you are reasonably certain that the pH and TA are accurate, then add 7 pounds of baking soda and retest pH and TA after 1 hour.

Do you have the calcium reading?

Also, you should lower the cyanuric acid to less 80 ppm if you have a salt system, or less than 60 ppm if you don't have a salt system.

 

[chem geek]

I would not trust the TA reading given it's strange color. I'd just get the pH up first, then deal with the monochloramine using chlorine, then after all that is done you should be able to get valid test results for TA. If you use pH Up (Arm & Hammer Super Washing Soda), then you'll increase both pH and TA so even if the TA is too low this should be OK (and you can always adjust TA more after taking care of everything else). After you've raised the pH, it will take only a few ppm FC to get rid of the monochloramine, so I'd just add around 5 ppm FC and see where things end up (again, do this AFTER you've raised the pH since getting rid of monochloramine is going to lower your pH more).

Where are you getting your "TC" number? Is that from the OTO test? TC = FC + CC so you can't have 0.5 ppm TC. Based on your FAS-DPD FC and CC readings, TC would be 6.0 ppm.

And why is your CYA number so high? Have you been using stabilized chlorine? Was your CYA high before the storm?

 

[Melt In The Sun]

Thinkly,
Please ditch those tabs, for your own good!

 

[Thinkly]

I admit that I have been using trichlor and dichlor to treat my pool. I know that has left me with a high CYA problem that i tried to address by draining 80% of my pool earlier in the season. Even with doing that I wasn't able to get the CYA to read below 100.

Regardless here is where I am at now. I have raised the TA to 150 (too high I know) using baking soda. The pH continues to @ 6.8. My FC today was .5 and my CC was 7. So I went out and bought 6 gallons of bleach and added to pool. Immediately following that my pool water started turning a yellowish color. Prior to the addition of the bleach I could already see my pool walls leaning in the direction of turning yellow again although it was faint. Now the water is a very distinguishable yellow and smells very "chlorine" like. Or is it the CC I am smelling?

Anyway, I also have my returns pointing up and shooting the water several inches above the water surface to try and raise pH. I will test again after the water has had a good deal of time to circulate. Should I be concerned about the sudden shift of the water to a yellow color?

 

[JasonLion]

You appear to have iron in the water, which is what is causing the yellow color. I suggest adding a startup dose of sequestrant.

You have allowed the PH to get way way too low, which may well have caused some damage to the pool.

 

[chem geek]

It sounds like the low pH may have corroded some metal in the pool equipment putting iron into the water. That's not good. Using Trichlor isn't just a problem due to the buildup of CYA, but it is very acidic so unless you are monitoring both pH and TA, you can have the TA get exhausted and the pH crash. This is just one of several reasons why we don't recommend Trichlor as the sole source of chlorine if one wants a Trouble Free Pool.

By the way, I contacted Taylor about the TA test and they said that purple in that test is an indication of biguanide in the presence of no alkalinity. However, I don't think it's biguanide, but perhaps the algaecide you used. Do you still have the bottle and can you tell us the ingredients?

 

[Thinkly]

It sounds like the low pH may have corroded some metal in the pool equipment putting iron into the water. That's not good. Using Trichlor isn't just a problem due to the buildup of CYA, but it is very acidic so unless you are monitoring both pH and TA, you can have the TA get exhausted and the pH crash. This is just one of several reasons why we don't recommend Trichlor as the sole source of chlorine if one wants a Trouble Free Pool.

By the way, I contacted Taylor about the TA test and they said that purple in that test is an indication of biguanide in the presence of no alkalinity. However, I don't think it's biguanide, but perhaps the algaecide you used. Do you still have the bottle and can you tell us the ingredients?

Here is the link to the algaecide I used. http://scorecard.goodguide.com/chemical ... %20CONTROL

My current situation is I have a high TA ~ 160 and my CC was 1 last night. TC was around 14. My pH is still 6.8 even with aeration. I currently have my pool slide running and my returns turned up. I will retest tonight and see if my pH has budged. The yellow color in my pool has subsided although I don't know why. I have not added a metal sequestrant up to this point.

I am planning to close the pool on Tuesday of next week so all of this is an effort to get my water balanced before closing.

 

[chem geek]

As shown in the PAN Database the ingredients are linear quat algaecides. These do create a chlorine demand and break down over time, but not immediately. You must have seriously overdosed in order to get such a high CC level so quickly. At least you now have a significant FC level in the pool, though with your very high CYA level at 100+ it's hard to know how much chlorine would be needed to prevent algae growth. You are going to need to lower the CYA level. If you get winter rains, then that would be a good way to dilute the pool water via overflow (unless you are in a freezing climate and need to close the pool -- in that case, you'd have to let rains get into the pool and manually remove water to lower the level and keep it at winter closing level).

You still need to get the pH up. Now that your TA is higher and the CC is lower, is the TA test behaving normally going from green to red? As for raising the pH, adding anything to raise it will also raise the TA further. Only aeration can raise the pH without raising the TA, but at this point we have no idea how low the pH really is though I suspect it's not that low anymore given the TA reading (i.e. it may be in the 6.5 to 6.8 range). If you want to add something to get the pH up but not increase the TA too much, you can add 20 Mule Team Borax.