Low TA, High PH, and 0 CYA before a SLAM

[ba67]

We just opened up our pool and the water is extremely green. I tested the water and it shows that TC is 0, CC is 1, TA is 50, PH is 7.8-8.0, CH is 100, and CYA appears to be 0. Before I start the SLAM, I assume that I need to lower the PH, increase the TA and increase the CYA to 30. I plan to use liquid CYA to increase the CYA since I already have some on hand. Before I add anything I have a few questions:

1. Which chemical should I add first--the muriatic acid to lower the PH, the baking soda to increase the TA, or the liquid CYA to increase the CYA?

2. How long do I wait after adding each chemical and how long do I need to wait after adding the last one before starting the SLAM?

3. What TA and PH number should I shoot for when making my calculations on the pool math calculator?

I've done a SLAM multiple times before but I've never opened up to water that was high in PH but low in TA before. Normally, when I open up our pool to a swamp, TA and PH are both low. I'm not sure how to proceed in this situation so any advice is greatly appreciated.

 

[mknauss]

Have you run the pump for a day and brushed the pool really well to be sure it is well mixed?

 

[ba67]

Have you run the pump for a day and brushed the pool really well to be sure it is well mixed?

Pump has run for 3 hours. The company that opened it brushed it well and blindly vacuumed it to waste to get rid of the leaves that blew past the cover. I really wanted to start the SLAM tonight unless there is some reason why I should wait. I'm leery about adding muriatic acid though because I have a feeling that the PH is lower than the test indicates since it is never high when I open it.

 

[mknauss]

Add chlorine - 10 ppm FC. But wait on baking soda and/or acid until tomorrow. Start the CYA tomorrow after you test.

 

[ba67]

Add chlorine - 10 ppm FC. But wait on baking soda and/or acid until tomorrow. Start the CYA tomorrow after you test.

After running the pump for 24 straight hours, I tested my water again and it looks like PH went down to 7.6 but TA is still at 50. CC is zero this morning, which is odd since the water is extremely green. Since baking soda increases PH and muriatic acid lowers TA, what should I do? Since a TA of 50 is an "acceptable minimum" according to this site, and PH is only slightly high at 7.6, could I just start the SLAM and add nothing, except some liquid CYA? I hate handling muriatic acid so I'd love to skip it if it wouldn't impede the process of clearing up the pool.

 

[mknauss]

CYA will lower pH a bit. Just add enough CYA to get to 30 ppm and start the SLAM process.

 

[ba67]

CYA will lower pH a bit. Just add enough CYA to get to 30 ppm and start the SLAM process.

I didn't realize that liquid CYA would lower PH. Could it lower the TA too?

 

[mknauss]

I didn't realize that liquid CYA would lower PH. Could it lower the TA too?

Not appreciably.

 

[JamesW]

I didn't realize that liquid CYA would lower PH. Could it lower the TA too?

Regular CYA lowers the pH slightly and has no effect on the TA.

CYA is a "weak" acid like carbon dioxide and weak acids do not lower the TA.

Liquid CYA raises the pH and TA slightly.

Liquid CYA Is sodium cyanurate, which is similar to CYA but with fewer hydrogen atoms.

 

[JamesW]

Chemical Composition 35% Sodium cyanurate.

pKa = 6.88

pH 8.5 - 9.5.

Monosodium cyanurate monohydrate

CAS Number 2624-17-1

Weight % 35-42%

 

[ba67]

CYA will lower pH a bit. Just add enough CYA to get to 30 ppm and start the SLAM process.

Thanks for all of your advice. I added the liquid CYA and it lowered the PH to 7.4 and it didn't appear to lower the TA.

 

[JamesW]

I added the liquid CYA and it lowered the PH to 7.4 and it didn't appear to lower the TA.

Liquid CYA should slightly raise the pH.

What brand did you get?

Does the label show the ingredients?

 

[ba67]

Liquid CYA should slightly raise the pH.

What brand did you get?

Does the label show the ingredients?

Natural Chemistry Instant Conditioner. It says that it contains Sodium cyanurate.

 

[JamesW]

It says that it contains Sodium cyanurate.

That would slightly raise the pH, so not sure why your pH seems to have went down.

In any case, not a big deal either way.

 

[IceShadow]

Could just be more mixing. The water might have still been a bit stratified.

Alternatively, how are you chlorinating the pool?