Counteracting low pH caused by adding CYA

[brianmcb]

I'm adding a lot of CYA since my level was 0, close to 12 lbs (added 6 lbs so far, doing 2 lbs at a time).

According to the pool calculator, this will lower my pH by 1.3. I tested my pH tonight and it's already down to 6.8 or below. Should I be dumping a whole lot of borax in to counteract this? Should I do it now or wait until I'm done?

 

[coloeb]

You are at risk now of damaging your plaster.get your ph back to 7.2 or so. If you can airate the water with a fountian, spa jet etc. Try not to add anything untill you know what your test numbers are. TA, CH, PH, all need to be considered before advice can be given. Do you have a good test kit? If not take a sample to the pool store to be tested.

 

[chem geek]

Use Borax to raise the pH. The Pool Calculator is overestimating the effect of 12 pounds of Cyanuric Acid. It depends on your TA level, but even it was only 50 ppm the pH would drop from 7.5 to 6.7. With 6 pounds, it would drop from 7.5 to 6.9 so you might have started out below 7.5 or the TA is quite low. Anyway, add some Borax to raise the pH since you don't want the pH to get below 7.0. I wouldn't add any more CYA until you get your pH higher. Then when you add the other CYA, add some Borax afterwards.

16 pounds of CYA in 20,000 gallons is around 70 ppm -- is that what you wanted, assuming you were starting with zero?

 

[brianmcb]

Thanks for your responses!

I have the tf-100. I am not positive that my pool is 20,000 gallons, this is my first year with it. I had two pool companies give the same estimate, and so far it's seemed somewhat close when figuring out chemicals to add.

I added 4 lbs of Borax right before my post. I checked pH again and it's up to 7.5. This seems odd since the calculator says it should have only risen 0.35.

Here are my current test results:
FC: 8.5
CC: 0.5
TC: 9
pH: 7.5
TA: 60
CH: 210 (i have added 8 lbs of calcium chloride since I tested earlier today and plan to add another 8 lbs to get to 300)
CYA: Did not test since I just started adding it last night

My pH was 7.2 when I started adding the CYA. I am shooting for 70 ppm.

FC is high because I shocked last night and have had my SWG on all day.

 

[chem geek]

It's possible the Borax wasn't yet thoroughly mixed throughout the pool so the pH you measured was locally high. With your numbers, I calculate that if you started with a pH of 7.5, then the 6 pounds of CYA would lower the pH to 6.96 and then 4 pounds of Borax would raise the pH to 7.26. So something is odd, but I wouldn't worry about that now -- your pH is in better shape.

 

[brianmcb]

ok thanks a lot! I'll take the CYA out until I can get some more Borax tomorrow.

 

[duraleigh]

Perhaps just a little too late but a pH of 6.8 or so is not going to hurt your pool in any way for a few days.

It's chronicly low pH that is harmful.

 

[chem geek]

True, but since there was no initial pH given we really didn't know how low the pH really was since 6.8 is the lowest reading in the test. I agree, not a huge deal. Brian, basically, it's not urgent that you remove the CYA -- if you want to leave it in and add the Borax after you get it tomorrow, then that's fine too.

 

[brianmcb]

Another question:
isn't adding all this Borax going to raise my TA too high? I tested today and it was up to 80 already, from 60-70 a few days ago. I'm still adding CYA. Shut my SWG off since FC is rising and my water has been clear for a couple days now.

here are my numbers from today:
FC: 9.5
CC: 0
TC: 9.5
pH: 7.2
TA: 80
CH: 270
CYA: 30

 

[brianmcb]

for now, i've setup a pretty ghetto aerator using a submersible pump, hose and hose head on "shower" setting. it isn't a very strong flow but it definitely creates a lot of water droplets.

 

[chem geek]

The Borax will raise the TA about half as much as a pH Up (sodium carbonate or washing soda) product. If you want to raise the pH without any change in TA, then aerate the water. That only works well, however, if the TA is on the high side. When the TA is already not too high, then it takes a lot of aeration to get the pH to rise. Up to you what you want to do.