High TA, LOW pH - What do I address first?

[rodrigo]

Everything I know about pool care I learned from pool contractors and stores. Much of it is suspect, I'm finding. I am re-teaching myself everything I know about pool care after 5 seasons of pool ownership! I found this forum *this week* after suffering a sudden, major algae bloom. I really DO want to do it the right way.

I live in Central Illinois, and have a 10K gallon fiberglass, in-ground pool with automatic cover. I run an Aqua-Rite SWG and sand filter w/ZeoBrite. The cover is closed most of the time during the week, and I run the system timer to filter about 10 - 12 hours daily, depending on usage.

Traditionally, my TA has always run high, around 150 or 180 -- but I never worried as the water looked clear. I've battled CYA since the beginning. It's a struggle to even get it to register -- but haven't worried too much as I never seemed to have problems maintaining acceptable TC. In fact, I often had TC on the high side -- which I always assumed was due to the pool being covered all the time.

After reading MANY posts on this forum, I have officially renounced test strips. The kit from TFTest is on the way. However, the strips are all I have at the moment - and I'm growing concerned.

I rolled back the cover on Tuesday to discover the water had turned. It was fine (or so I thought) on Sunday when we closed it up. Test strips showed zero FC, pH around 7.4, TA very high - around 200, CYA at ZERO. I shocked the pool to get some chlorine in there, and discovered my SWG had shut down due to inadequate salt levels (which tested fine 5 weeks ago when I opened the pool). I added salt to get back up to 3100 ppm. I began adding acid to bring down TA first, with intent of getting pH back in line thereafter.

NOW, I have TA still a bit high at 120, but the pH is VERY low, at 6.2 (as close as I can tell with the strips). FC is high at 10 ppm or more (the square is DARK purple). CYA still reads zero. The water is now a very cloudy white - an improvement from the cloudy green I had earlier this week.

I have read about aeration, and purchased components to build a bubbler to run on my air compressor. I'll get that going tonight. However, I'm worried about this extremely low pH, and what it may be doing to my cell. The heater is OFF.

So, do I start aeration immediately with such a dramatically low pH? Does the addition of CYA tend to force pH even lower? Should I add that now? later? If I aerate now, do I just monitor pH until it gets to 7.6? AND, can I do all this with the test strips I have on hand?

Thanks, in advance, for any and all advice.

 

[JasonLion]

Welcome to TFP!

You never should have added that much acid all at once. Low PH like that can cause damage, and the only way to raise it quickly is going to raise your TA back up. You should add borax (if you have it or can get it quickly) to get your PH up to at least 6.8 as soon as possible. If you don't have/can't get borax, you can use soda ash/washing soda/PH Up, but that will raise your TA even more than borax will. Once the PH is up to 6.8, you can use aeration to raise it the rest of the way.

Wait to add the CYA until your PH is at least 7.2.

Long term, I would not trust the test strips. Still, for PH they usually work acceptably. You might as well continue using the test strips until your new kit arrives.

 

[rodrigo]

I guess I didn't technically add the acid all at once. I put it in in about three doses, separated by 8 - 12 hours. I was following the advice from the pool store in a neighboring town. *cough, cough* They said to get your TA in line first, THEN add pH up to get the pH right.

I'm on my way to get some borax.

Should I start aerating?

THANK YOU!

 

[duraleigh]

Should I start aerating?

No. Aerating is a slow, slow process to lower TA. Use 20 Mule team borax to raise your pH back into the 7's and then post your pH result back.

You are trying to do too many things at once. Get your pH back up safe and we'll go from there.

 

[rodrigo]

OK, I'm feeling better about things!

Since my pH was so drastically low, I added two 76 oz boxes of borax to my pool last night, over the course of an hour. Readings last night and this afternoon are as follows (and remember, I'm still using strips as my *real* test kit has not yet arrived):

pH - 7.5 (an estimate, I only have color codes for 7.2 & 7.8, the color appears about halfway between).
FC - 10 (or higher - it's VERY dark purple)
TA - 150 (estimated - it's halfway between the colors I have for 120 - 180).
CYA - 100

I have a few questions:
* According to the pool calculator, to go from pH 6.2 to 6.8 should have taken over 13 pounds of borax. I added less than 10 pounds, and overshot 6.8 by a lot. Is that a result of using a poor measurment tool (strips)? Not really knowing the volume of my pool (more on this later)? a combination?
* Why does the CYA suddenly register at 100 ppm when it read zero for so long -- especially after RAISING the pH?
* How does one go about deciding what their preferred pH and TA should be? I'm running a SWG, so whatever advice anyone can provide on sound targets is needed and appreciated.

A Note on my pool volume: After 6 years, I STILL am not really sure how much water my pool holds. The builder told me the shell held 18,000 gallons. When I finally figured out that was not even close to correct (my numbers swing around WILDLY with whatever treatment I was trying), I called the manufacturer (Viking Pools), who told me it was 12,400 gallons. A couple of summers ago, my son and I got out a measuring tape to conduct our own survey of the pool. We calculated the volume in cubic inches, which we then converted to 10,667 gallons. Since then, I used 10K for all my treatment calculations. I felt pretty good about our math until yesterday. I'm wondering again because the Pool calculator called for way more Borax than I needed...

I pledge to do better!

Thanks again.

 

[JasonLion]

PH shifted by more than you expected because test strips are not reliable for water testing.
CYA suddenly changed because test strips are not reliable for water testing.

You really need a top quality test kit.

Ideally you want TA around 60 to 80 and PH between 7.5 and 7.8. See this article for detailed advice.

 

[frustratedpoolmom]

I agree, you need a way to reliably measure the CYA, because if the CYA really is 100....it makes more sense to drain/refill to lower the CYA first rather then spend time and money adjusting other chems only to have to rebalance later....