Help with interpreting CSI

[kal2002]

Hi everyone. I received my TF100 test kit yesterday and I got the following test results:

pH - 7.8
FC - 5
CC - .5 (It was 0 and then the water turned slight pink after a few minutes)
TC - 5
TA - 130
CH - 470 (It was 450 until it turned purple from blue so I added 2 more drops)
CYA - 45
water temp - 78 degrees

I put all this info in the pool calculator and the CSI is 0.59. What does this mean? Should I be concerned with it being so close to .6?

Thanks.

 

[Bama Rambler]

Disregard the CC. It's normal for it to turn back pink after a minute or so.

If you adjust the numbers a little you can get the CSI close to zero.

 

[duraleigh]

I don't use the CSI but what it is telling you is the combination of your CH, TA, and pH "adds up" to being too high. (I know, that's a red-neck way of putting it)

If you lower your pH down to around 7.2 and drop your TA to around 90, You can likely leave your CH right where it is and the CSI will then be in a better range.

 

[Richard320]

Simplified CSI: If the number is positive, the water's getting full and will likely start leaving calcium deposits somewhere. If it's negative, it will start pulling calcium from somewhere - previous deposits or the plaster walls.

In your case, you're very close to forming scale. Lowering the pH will also lower the CSI. It will have a slight effect on TA. The pH will rise again, and you'll have to dose it again, until the TA gets down to double digits somewhere and things will stabilize somewhat.

The nice thing is, it doesn't take very much acid to lower pH to an acceptable level. A couple of cups max. You can accelerate the process of lowering TA by aeration - run the spa, turn on a fountain, aim the return jets up. If you search aeration you'll find plenty of threads.

 

[kal2002]

Thank you for your help. I tested the water again this morning. The only change is FC went from 5 to 3; CYA went from 45 to 35; water temp was 82. So I turned on the fountain as Richard suggested. I also added 6 3" chlorine tablets (trichlor) in the floaters since, from what I read, they will reduce PH and TA. The CYA is still fairly low so I assume that the trichlor will not increase it much in a few days.

So should I test the water again this evening or should I do it tomorrow morning to see if any readings have changed? Thanks.

 

[anonapersona]

What Richard said was

The nice thing is, it doesn't take very much acid to lower pH to an acceptable level. A couple of cups max. You can accelerate the process of lowering TA by aeration - run the spa, turn on a fountain, aim the return jets up. If you search aeration you'll find plenty of threads.

That is, FIRST add the MA, THEN do the aeration. Test TA again before adding more MA, as when it changes it affects the volume of MA you need next time.

Read Pool School http://www.poolcalculator.com/chemistry.html about TA

 

[kal2002]

Ooops. I misunderstood. Thanks. I turned off the fountain. I don't have any MA so I will have to get some. I think I will get the dry acid instead. I am new to pool maintenance. I will need to stock up on some basic pool chemistry supplies.

 

[kal2002]

I found a gallon of hydrochloric acid that came with the pool. Google tells me that it is muriatic acid. But this stuff is at least 2 years old. Does anyone know if it is still good?

 

[Bama Rambler]

It's most probably still good. Use the amount the pool calc tells you to and test it again to see if it changed it the amount it was supposed to.

 

[kal2002]

The pool calc says to add 85 oz of 31.45% 20 Baume to get the pH from 7.8 to 7.2. I don't know what strength my MA is. Can I assume that it is 31.45% 20 Baume? The label on the pitcher does not tell the strength either.

 

[zea3]

Assume it is 31.45% 20 Baume and dose the pool accordingly. Test the pH again in 30 minutes. If it did not lower pH as much as it was supposed to then you have a weaker batch of MA.

 

[kal2002]

I added 2.5 pints of MA into the pool. The instructions on the label says to add 1 pint per 10,000 gals of water and do not add more than that within 24 hours I will test the pH in 30 minutes and see if it did anything.

 

[duraleigh]

If your pH was 7.8, that dosage should get you to 7.6. I would suggest keeping your pH not higher than 7.4 so that would mean another dose. You can disregard the 24 hour thing and put it in immediately if you like.

 

[kal2002]

Hi Dave, Thanks. I just did it. I will test the pH in 30 min. Kind of anxious to find out the new ph reading.

 

[kal2002]

Just retested ph, TA and FC. I added 3 pints (48oz) of MA after Dave said I did not have to wait 24 hours and pH did go down to 7.3. I called it 7.3 because it is a little redder than 7.2. TA is about the same - 120. FC is at 4. Now the Pool Calculator says CSI is at .14. This is pretty amazing. By the way, the pool came with scaling - the white ring above the water line. Now I know how it got there.

 

[anonapersona]

NOW you can turn the fountain and such back on. This will make the pH go up but TA will stay reduced from 130 to 120.

Since you were pretty much on target with it last time, next time you can go to pH 7.0 and aerate and repeat as needed. Again, I suggest that you test TA before you do as if it has changed it will affect the volume of MA you need.

Dry acid is fine but just more expensive. MA is wicked stuff as you may have noticed.

 

[kal2002]

You guys are so very helpful and I am learning a lot today. Thank you so much.

Yes, MA is strong smelling. This is my first time handling it. Next time I will hold my breath when I do the measuring.

So you are saying that each time I want to lower TA, I should lower the pH to 7.0 or 7.2. After TA drops, increase pH back to the normal range. And I can keep doing this process until I get to the desired TA level?

Another question: can I increase ph by adding borax instead or will this be too many chemicals in one day?

 

[Bama Rambler]

The best way to raise pH when trying to lower TA is to aerate. Adding Borax to raise pH raises the TA a little so you're kind of see-sawing if you do that. Aeration is best.

 

[kal2002]

After adding MA yesterday, here are my test results this morning:

pH - 7.3
FC - 2.5
CC - 0
TC - 5
TA - 90
CH - 400
CYA - 35
water temp - 80 degrees
CSI - -0.1

FC decreased so I will need to add more chlorine to bring it to 4 or 5. pH did not change from 7.3 but TA went down more than I expected. CH also decreased a lot. I tested it both ways. I did the alternative testing procedure first using less water (10ml) and the result was 400. I retested it using the regular procedure (25ml water) and I got 310. I thought CH does not decrease unless water is replaced. Any thoughts on this one? Thanks.

 

[duraleigh]

I retested it using the regular procedure (25ml water) and I got 310. I thought CH does not decrease unless water is replaced. Any thoughts on this one?

Your correct it does not change. Either result is fine so just chalk it up to experience and disregard it. CH has a big range (200-400 ideal) so you are within that range and have nothing to worry about.

Likewise, I would leave your TA and pH alone for now. Concentrate on maintaining your FC in a 3-5 range and you'll never have an algae or sanitation problem.

Sounds to me like you are virtually right where you should be. Keep your filtration adequate, watch your FC closely and you'll have a troublefree pool the rest of the summer.

CYA and pH and TA may need tweaking in time but for now I would leave all of them right where they are. If you still have some CYA left over, you could bring it up to 50ppm but I wouldn't buy a whole big jug of it for that little bit of correction.