Newbie midway through SLAM very low PH

[rscam]

Hi all. New here, loving this site. This is my first season as pool owner (bought house) opened pool to swamp. Been following the "Turning Swamp to Oasis" sticky. I've been doing well I think but my PH seems to have dropped alot and am concerned, so I figured I'd post. Some background first. When I started numbers were

FC=0
CC=0
PH>8.2 (pool store said 8.5)
TA=40
CH=70
CYA<20 (Pool store said 20 but with my test the black dot was crystal clear I assumed there may be 0 due to the Ammonia levels
Ammonia = Approx 6ppm

At the time I tested for Ammonia with a fish tank kit I happen to have because the CYA was so low and I knew the previous owner used Chlorine tabs.

Before I started the SLAM I added 96 oz of 20% Muriatic Acid (It was a product called Klean-Strip Green from Home Depot - they claim that it has 90% less fumes than "standard" MA - as far as I could tell it is straight MA - so not sure what makes it "Green" other than that it is 20% so maybe lower than "Standard"?? I bring it up because its been in the back of my mind that maybe it contained additives that are not good - if anyone knows this product please chime in)

I also added 4 lbs by weight of Leslie's Stabilizer (CYA) since I wasnt sure about the reading and didnt want to raise it too far

I didnt worry about trying to adjust the TA yet (maybe I should have?)

I tested the PH the next day and it was at 7.2. Didnt bother testing CYA because I knew it would take a while to show up.

On 5/7/18 I Startedt the SLAM

As expected, I needed a TON of chlorine to bring the Ammonia to 0 and then I was able to attack the algae.

It has been going along OK. At this point the Pool is a cloudy Blue and I find it easier to maintain the FC SLAM level of 10 ppm but my latest tests show a VERY LOW PH=6.4?? (Taylor test bottoms out at 6.8 so used fish tank kit and got approx 6.4 maybe even lower (hard to tell color).

Current numbers

FC=10
CC=1.0
PH<6.8 (6.4 per fish tank test kit)
TA=30 (this seems to have gone down since starting?)
CYA=17 (I'm assuming 17 - I'm not good at test yet but it seems very close to 20 but not quite there and assuming I was indeed at 0 to begin per pool math it should be 17 based on the 4lbs added)

My questions are:
1) How concerned should I be regarding the low PH
2) Insight as to why it would drop like that? I thought adding all the liquid chlorine would bring it up?
3) Recommended course of action

PS unfortunately, after the initial testing - I've been focusing only on the Chlorine levels and not the PH so I'm not sure how gradual this decrease was

Thanks for the help
Ron
Here are pics from 1st day and now
View attachment 77365View attachment 77366

 

[funandsun]

I would not fret over the ph until you are out of SLAM, once mine is set and I enter SLAM, I don't test anything other than FC and then obviously CC when I am in the OCLT phase.

High FC will cause distorted pH readings, I know you mentioned 10ppm and that is typically considered the top threshold, I wouldn't change a thing, keep in SLAM until through OCLT and then make adjustments that are needed at that time.

Pool is really looking so much better, nice work!

 

[JamesW]

Oxidizing ammonia creates acid by releasing hydrogen.

2NH₄⁺ + 3OCl^- --> N₂ + 3H₂O + 2H⁺ +3Cl^-

When adding 12.5% sodium hypochlorite (liquid chlorine) to a pool to oxidize ammonia, every gallon of liquid chlorine will create the equivalent of 15 ounces of 31.45% hydrochloric acid.

10 gallons of 12.5% liquid chlorine added to 25,000 gallons of pool water with ammonia will lower the TA by about 23 ppm or the equivalent of adding 150 ounces of full strength 31.45% muriatic acid.

Every 8.53 gallons of 12.5% liquid chlorine is equivalent to about 1 gallon of 31.45% acid.

 

[funandsun]

yes, what JamesW said

I think that means, don't worry, everything is normal, continue as you were.

Oxidizing ammonia creates acid by releasing hydrogen.

2NH₄⁺ + 3OCl^- --> N₂ + 3H₂O + 2H⁺ +3Cl^-

When adding 12.5% sodium hypochlorite (liquid chlorine) to a pool to oxidize ammonia, every gallon of liquid chlorine will create the equivalent of 14 ounces of 31.45% hydrochloric acid.

10 gallons of 12.5% liquid chlorine added to 25,000 gallons of pool water with ammonia will lower the TA by about 22 ppm or the equivalent of adding 140 ounces of full strength 31.45% muriatic acid.

Every 9 gallons of 12.5% liquid chlorine is equivalent to about 1 gallon of 31.45% acid.

 

[JamesW]

I adjusted my numbers a little bit.

The pH only drops when oxidizing ammonia. When oxidizing algae, the pH should not change.

Also, cyanuric acid is an acid and will lower pH but not TA.

 

[rscam]

Thank you for the help James and Funandsun. So that explains the low PH. You really think I should just let it rise back up naturally? (I'm trying to aerate with the return jets pointed up) or should I add a PH increaser or try to bring up the TA with baking soda? I was unsure about PH reading (not really believing my eyes - but it may be even lower (6.2?) and it did take a TON of chlorine to bring down the Ammonia

 

[JamesW]

Just raise the TA with bicarb and the pH will follow.

 

[mknauss]

With a TA of 30 I suggest you add baking soda to increase that to 70 ppm. You will need to monitor the TA as it may drop as your pH rises due to aeration.

Take car.e

EDIT -- The TA will not drop as stated above -- sorry for the confusion!

 

[rscam]

Thanks. I am adding the baking soda now.