Help!!! PH through the roof

[mickey4paws]

We're closing the pool in the morning and so we added Polyquat 60. I let it circulate a while and then did a PH test. It's a bright magenta color
Is this normal or should I add acid immediately?

 

[duraleigh]

Not sure I understand...are you saying the polyquat altered your pH? Or are you saying it was that high before?

 

[Butterfly]

Did you shock your pool? High FC = possible false high pH reading.

 

[mickey4paws]

PH was fine earlier at 7.6. FC was at 4.5 and so I added 2 bottles of liquid chlorine (128 oz each at 9%) and FC is at 13.5 right now. The PH test I just did came out magenta, like waaay over 8.2

 

[mickey4paws]

Also, TA is 100. I tested it again and the same results. Here's a pic, not sure if you can tell how magenta it is.[attachment=0:yh9ehr4m]PHTest.jpg[/attachment:yh9ehr4m]

 

[duraleigh]

Are you testing pH with a comparator? What Brand? What reagent are you using?

 

[mickey4paws]

Hi Dave, I just edited my previous post and added a picture. This is the PH test that came with the TF100.

 

[duraleigh]

While the pH test in the TF-100 is not very reliable after 10ppm FC, I still think that test is too high (good pic, incidentally).

I would disregard that pH test if your FC is 20+ but if, in fact it is 13.5, you might bring the pH down a little with muriatic.

One last question before you do....you said it was 7.6 earlier.....how much earlier?

 

[mickey4paws]

This afternoon it was 7.6. We added the chlorine around 5 pm and the Polyquat around 6 pm. Do you think then that we should add some acid tonight? We're planning on letting the filter go all night.

Pool calc says to add 28 oz muriatic acid to go from 8.2 to 7.6. Does this sound good?

When I read my FC test, I was really low on the R0871. So I just redid the test using a new bottle of R0871 and FC is at 11.

EDIT: Just added 24 oz of acid and will then retest. Thanks so much for the replies. I've never had PH higher than 7.9 and it kinda freaked me out. We've only had to add acid twice this summer and have been able to maintain at 7.5 to 7.6.

Just ran another test, still getting that purple/magenta color. Maybe the acid needs to circulate more? I'm really thinking it has to be something to do with the Polyquat and hopefully is giving a false high reading

 

[chem geek]

Adding 2 gallons of 9% chlorine to 20,000 gallons starting with a pH of 7.6 and a TA of 100 would raise the pH to around 8.1 so what you are seeing is not that surprising and I don't think it has anything to do with the PolyQuat. 24 ounces of full-strength Muriatic Acid (31.45% Hydrochloric Acid) should have brought the pH back down to around 7.6-7.7. Is your acid full-strength or is it half-strength (15%)?

 

[mickey4paws]

Thanks so much for the reply, Chemgeek. I retested this morning and PH was still way high, around 8.5. I just added another 24 oz of acid (acid is 31%) and will retest in a while.

 

[mickey4paws]

It's been an hour since I added the 24 oz of acid. At first it looked like the test was going to be 7.6 and then all of the sudden it turned that dark magenta color again. I don't know what to do

 

[frustratedpoolmom]

What is the FC now? If it was 7.6 before the bleach addition I would still suspect false-reading.... the acid you added should have lowered it.

I would wait a bit I wouldn't add any more acid yet.

 

[mickey4paws]

FC is 9.5 (last night it was 11) and 0 CC. Since last night, we've added a total of 48 oz of acid and it hasn't budged. It was weird though because when I first inverted the test holder, it showed 7.6. Then all of the sudden, the test water turned that dark magenta color. I remember when we were converting from Baquacil and had high chlorine levels, our PH never shot up like it is now. I wonder if there was something wrong with the Polyquat that is causing this. I'm going to take a sample by the pool store since it's on my way to work this morning. But I think they use the same PH test as what I have (the one that comes in the OTO kit with the TF100).

Thanks so much for the reply, I really appreciate it!

 

[PaulR]

Would you be willing to try an experiment for me? If the pH test does that looks-okay-then-turns-magenta trick again, please do this: Dump and rinse the pH tube, get a fresh sample, put in a drop of R-0007 and mix, then put in the 5 drops of R-0014, and see what happens.

The R-0007 is thiosulfate, a chlorine neutralizer. There is some in the R-0014 already; I am suspicious that your pH test is starting out correct, then the chlorine is overwhelming the reagent. I've not seen this delayed reaction before so I want to see if extra thiosulfate will help.

Thanks,
--paulr

 

[mickey4paws]

Paul, thank you so much for the post. Unfortunately I'm at work now but I will do the test you say as soon as I get home around 5 pm. It sounds like you could be spot on.

Meanwhile, I stopped at the pool store on my way to work to have the PH tested. The guy said that because the chlorine is high, it will give a false reading. He says what to do is as soon as you invert the test tube, what you first see is your reading. He said it will continue to get darker and darker and turn that magenta color. His initial first reading was 7.4 (mine at home was 7.5).

So do you think he's correct? That would go with what you all have said too. But I could swear that when we were doing our Baquacil conversion and chlorine levels were high, that I tested PH and it was fine.

I feel like such a dummy if that's all it is. But, I also feel relieved if it is too.

 

[chem geek]

I suppose that it is possible for the PolyQuat to interfere with the chlorine neutralizer in the pH test as that would be consistent with what you are seeing. Doing the thiosulfate addition first that Paul suggests would help determine if that is the case (assuming the PolyQuat isn't so strong as to interfere with the thiosulfate that you add).

 

[mickey4paws]

Would you be willing to try an experiment for me? If the pH test does that looks-okay-then-turns-magenta trick again, please do this: Dump and rinse the pH tube, get a fresh sample, put in a drop of R-0007 and mix, then put in the 5 drops of R-0014, and see what happens.

Paul, I did your experiment and it worked I put in the R-007, mixed and then the R-0014. PH came up at a beautiful 7.5/7.6. I then emptied out the container and did the test without the R-007. At first it came up 7.5/7.6 but then started turning that awful magenta again.

So, now that our closing has been postponed a little, hopefully tomorrow, what should we keep our FC at? Should I keep the SWG going?
FC is at 8.5 with SWG running at 10%. Should we continue running the pump all night or would it be okay to shut it down for a while? It's been running continuously since Sunday morning.

Thanks again, I really appreciate the help!

 

[PaulR]

Thank you so much! I'm pleased that the extra-thiosulfate trick worked. I've been wanting to try that for a while but had no excuse in my own pool.

Unfortunately I don't feel competent to advise you about closing; I don't close (it's too warm here) and I haven't read enough about it to suggest anything you can't find in Pool School. If you're only asking about the SWG, leaving it on overnight will probably raise your FC a little but otherwise won't change much one way or the other.
--paulr

 

[frustratedpoolmom]

Are you going to cover? I would raise it back up to shock level with bleach and then winterize the pipes, cover, etc.

Next year, shock the pool until the FC holds overnight, then the next day add polyquat 60. Adding it within one hour of shocking caused the PQ to consume some of the chlorine and interfere with the FC tests, it seems like you had an overnight drop of 1.5. (I'm sure all is fine, I'm just suggesting to err on the side of pre-caution/prevention.) The PQ consumes the chlorine. So for added insurance since you did them so close together, shock again and then cover.

By shocking before you winterize, you are ensuring that anything organic in the pool is dead, thus make sure it's holding overnight. Then once it does (the next day, perhaps) you add the PQ for added insurance. The PQ will cause the FC to drop. Since you added them so close together, it is slightly concerning the combination won't be as effective, KWIM? I hope that makes sense....