Testing Post SLAM

[g3lo]

Hi,

So I am about ready to test my TA and PH for my pool as the FC drops to normal levels. It is hovering around 10-11 FC at the moment. A few more hours and the sun should lower it.

Could anyone chime in on the following;

1) Due to my pool being vinyl the recommended levels mentioned 50-90+ for TA. Does that mean as long as my TA is above 50, I don't adjust it? It also mentioned that no reason to drop TA if it is 150-160 just to get into the target level.

2) CH I don't worry about as long as its below 350

3) PH I can adjust with baking soda, however; if my TA is already 150-160 it will bounce most likely to near 200. Is that okay?

Please advise,

Thank you,
g3lo

- - - Updated - - -

I also read, that BORAX is better to raise your PH with as opposed to Baking Soda. Any advise?

 

[BoDarville]

I would focus more on managing pH than TA. Total alkalinity (TA) indicates the water's ability to buffer PH changes. So if your pH is relatively stable and within range (7.2 - 7.8), I wouldn't fiddle with TA unless it got below 50.

As for CH, although 350 is the recommended upper guideline for non-SWG pools, I wouldn't start losing sleep if it goes above that. We have members here (especially in the SW US) that battle CH of 800+. If CH starts rising significantly, you can compensate a bit by keeping pH on the lower side of the recommended range.

pH is not adjusted by using baking soda. To lower pH, muriatic acid is the preferred approach although you can also use dry acid. To raise pH, you can use 20-Mule Team Borax or Soda Ash.

 

[g3lo]

Thank you for your response. So here are my tests.

FC - 9-10
TA - 120
PH - looks like 7.8-8? I started SLAM with 7.2-7.3 is it possible that the SLAM made the PH climb that high? Or, am
I getting false readings because of a high FC?
CC - 0
CYA - 60

 

[BoDarville]

Since FC is now below 10 ppm, the pH results should be accurate. The SLAM may have increased pH a little vs. before you started- that's not unusual.

 

[g3lo]

I guess I should reduce it now? Water still feels like it's drying out skin

 

[BoDarville]

Yes, I would lower pH to the range of 7.2 to 7.8. If the pH in your pool drifts up (like mine does), I would adjust to 7.2 as that will lengthen the time it takes to drift back up to 7.8 which will result in fewer adjustments. If your pH doesn't drift up much or if it drifts down, then I would adjust to 7.5.

 

[pooldv]

Go ahead and test CH and enter all your test results into Poolmath and tell us what your CSI is. Keeping CSI between -0.3 and +0.3 often helps water feel on the skin. So does adding 1500-2000 ppm of salt. Tweak PH and TA to adjust CSI. PH, TA, CH, borates, CYA and salt all impact the CSI.

 

[g3lo]

Okay so here are my test results.

FC - 5.0 (will raise to 9 according to CYA/FC chart)
CYA - 60
TA - 115
CH - 150
CC - 0
PH - 7.7 (close to 7.8 but not quite)
CSI - 0?

Skin feels slightly dry to swim. What do you recommend? Otherwise, water is great!

 

[pooldv]

The numbers look good. CSI at 0 is great. Does your PH tend to rise? If so, then adding acid to lower PH will lower TA over time. I think lower TA, 70 or 80, might help the water feel a bit. Also, adding 1500-2000 ppm or so of salt will help.

 

[g3lo]

Thank you. Not sure how PH is in my pool as this is the first year using this method. How would I add Salt? And what kind of salt? Next tried it before

 

[pooldv]

Pool salt is sold in 40 lb bags, I buy mine at Lowes. You could add 8 or 9 bags. Just pour it in and brush it around for a bit.

 

[BoDarville]

Not sure how PH is in my pool as this is the first year using this method.

I would keep a log of your test results for at least a one-year period. Weekly recording is fine in order to see any general trends. To be clear, you should test chlorine levels daily, pH 2 - 3 times per week, and TA once a week. CYA, CH, and Salt can be tested monthly or more frequently if you have added anything that will impact these parameters. You only need to record the results of one set of tests per week in your log. I usually record the tests I run on the weekend for consistency.

As for adding salt, you broadcast it into the pool then brush the pool to help it dissolve. It will dissolve fairly quickly but you don't want it to just sit on the bottom of the pool until it does. Run the pump to help with circulation. BTW, it is better to add a little less salt than you think you need. Upon testing, if you feel you need to add more, it is easier to do that than it is to reduce it if you overshoot your target. Use salt that is labeled for use in pools which should be relatively easy to find. Use a salt that is at least 99.8% pure sodium chloride (NaCl). Avoid using salt with anti-caking agents like sodium ferrocyanide, also known as Yellow Prussiate of Soda (YPS). These cause some discoloration of fittings and pool surface finishes.

 

[g3lo]

Thank you for all that information. Mind you my pool is chlorine pool. How will salt affect my FC levels? Also, 8-9 bags of 40lbs? That seems like a lot.

 

[pooldv]

It will have no impact on your chlorine level. It will give you close to 2000 ppm of salt. A saltwater pool has about 3500 ppm of salt and the ocean is about 35,000 ppm salt.

 

[g3lo]

So after I drop the salt in to raise to 2000 ppm, I maintain the FC per usual?

 

[pooldv]

Yes, everything remains exactly the same.

 

[g3lo]

Great thank you. What if algae comes in and I have to do SLAM again, salt will not affect it?

 

[pooldv]

Nope.

 

[g3lo]

Thank you. So I checked 2 days now and my chlorine holds up from about 9-10 FC overnight to 5-5.5 the next day. Not too bad!

- - - Updated - - -

From night to next night****

 

[pooldv]

Have you done an OCLT? Here's how, Overnight Chlorine Loss Test