Opening balance question? Why bring pH does in a cold pool?

bryantdr

Well-known member
Jul 21, 2015
60
Long Island, NY
Opened my pool this weekend, and had some questions in how to balance chemicals.

My opening reading was:
PH:8+ (bright pink)
TA: 30
CA:100
Water temp:60 degrees F

According to the taylor Saturation Index that puts me at -.5 which is corrosive. I know slam instructions say take the PH down to 7.5, but that would just make the Saturation Index even worse. Given I will be doing a ton of vacuuming and filtering I didn't want to add CA, which takes a bit to dissolve, and would probably be vacuumed up. I also didn't want to up my TA, because I will just need to bring it back down when I add acid to lower my PH later.

My plan was to leave everything alone until I have the pool clean, and don't need to vacuum, or back wash constantly. Then I will add acid to take down my PH, CA, and finally take my TA up so my Saturation Index comes down.

I am keeping my Chlorine at the proper slam levels throughout.

Does that sound logical, or am I missing something?
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
12,869
Northern NJ
How about a full picture of your water chemistry - FC? CH? CYA? Salt? Is CA CYA or CH?

We use CSI calculated with PoolMath Depending on what assumptions I make about the missing values your CSI may not be that bad.

You have to raise your TA to at least 70 before you begin lowering your pH using MA. Adding MA will further lower your TA along with your pH. PoolMath will tell you the effect of adding chemicals.

Why are you doing a SLAM Process? The SLAM Process process does not work properly with high pH. You need to get your pH down to 7.2 before you raise your FC above 10 and begin the SLAM Process.

I suggest you review ABCs of Pool Water Chemistry
 

bryantdr

Well-known member
Jul 21, 2015
60
Long Island, NY
I'm giving you the opening pool values. FC was of course 0, and by Ca I eat referring to CH (100). My CYA is 20 or less. I don't add salt. The pool calculator seems to get the same Saturation guidance as the taylor wheel, but the pool math guidance -0.6, is less conservative than the taylor wheel -0.3.

I have been following TFP method fairly closely with good results. However, my question is: is it critical to get the pH to 7.5 or lower, or is it more important to keep the Saturation Index levels from creating a highly corrosive environment. I get it that slam may be more effective at 7.2, but maintaining my CH between 10 and 15 had been pretty effective at clearing the pool up while I still work to vacuum/filter out all the crud.

I didn't see it in the ABCs, but do you usually start adding Acid, CH, and Banking Soda to the water while it is still full of leaves and dirt. I have a gut reaction to hit it with Chlorine and start vacuuming/filtering before adding chemicals I am just going to vacuum out anyway. Plus, I need to get a lot of the stuff out before I am confident the water is circulating well, and any chemicals I add will be well mixed.

However, I'm not the pool expert, so I defer if you tell me it is fine to spend the first 24 hours, keeping the pool as a swamp and getting the balance right, before adding Chlorine.

It is also harder here in the NE, because the water temp is 60, which makes things more acidic, so what would normally be fine PH/TA levels are now corrosive.
 

bryantdr

Well-known member
Jul 21, 2015
60
Long Island, NY
One more question. Can you expand on not lowering your pH until TA was at least 70. I didn't see that in the ABCs, and hasn't heard that before (I'm sure it's true, just want more details)
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
12,869
Northern NJ
Agressive CSI water takes months to develop any problems. A few days or weeks while you are cleaning up your pool will not be a problem. Below is what PM calculates.

Given your pH and TA I would get your TA up and pH down before beginning the SLAM Process. Adding high FC levels causes the pH to rise back up from the 7.2 start and the CL effectiveness is greater that way.

Your worries about "acidic" and "corrosive" are unfounded for a CSI above -0.6 for a short time.

100917
 
Last edited:

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
12,869
Northern NJ
One more question. Can you expand on not lowering your pH until TA was at least 70. I didn't see that in the ABCs, and hasn't heard that before (I'm sure it's true, just want more details)
You don't want your TA below 50-60. 30 is way low and adding enough MA to reduce your pH from 8.2 or more to 7.2 can drive your TA down by 10 or more. I want to get the TA up to 60-70 before I drop the pH/TA down.

100920
 
Last edited:

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
12,869
Northern NJ
Lower your pH in small doses. Use PoolMath and say your pH is 8.2 and target is 7.6. Add the recommended dose of MA. Retest pH and TA and repeat until you get a pH reading in the 7's. Then make a final adjustment dose from that value to 7.2.

Do you have a heater? Do you have a heater bypass valve? If so bypass your heater while making the pH adjustments and even during the SLAM Process. This protects your heater if you overshoot your pH and get it too low.
 
Last edited:

bryantdr

Well-known member
Jul 21, 2015
60
Long Island, NY
I do have a heater, but no bypass valve. I will go slowly taking PH down.

Unfortunately I already jacked up my Chlorine to clean up the pool. It may be less effective, but it is doing an okay job so far.
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
12,869
Northern NJ
When your FC is below 10 add bicarb to raise the TA to 70 ppm, and then immediately add about one quart of acid. If the pH is above 8.4 (it is possible that it is), then adding bicarb will help lower the pH too along with the acid.

The added bicarb will buffer a quart of MA easily. Then once the pH is confirmed to be below 8.0, then calcium level can be raised.
 
Last edited: