Test Kit Arrived

[JasonLion]

Plaster effects depend on a combination of several different levels and just how far off they are. The levels you originally posted showed CH and PH high, but TA on the low end of normal. The low TA will partially cancel out the high PH and CH levels. Given reasonable assumptions of just how high the PH went, the odds favor no problems in just a week. However, if PH went up to 8.8 or above, which is unlikely, then I would expect there to be some calcium scaling after a week.

 

[Richard320]

Ok reread pool school and I think it might be starting to sink (haha) in. Just a lot of information.

I need to keep doing MA treatments to lower the ph to 7.6. Then add baking soda to bring TA (because MA will lower it) to 60-80.

One thing that the articles do is warn you of what can happen when chemicals are out of the suggested ranges. However it doesn't tell you how quickly problems can arise. If ph is high for a week or two or TA is low for a while, does that have great affects on the plaster?

Plug your numbers into poolmath and see what it gives you for CSI. Zero is perfect, but anything within +/- 0.5 is okay. Your CH is on the high end - I have the same problem - so pH is pretty critical. You can start growing scale within a couple weeks if the CSI is positive.

The good news is, now you're in control. You'll start seeing the results as you test and dose and soon it will be really easy. Two months, maybe three since it's not swim weather, and you'll look at your old posts and wonder how you ever got confused. Really!

 

[Jabooh1]

I have looked in a few places, how do I do the Acid Demand test with the TF100? Or is there not a test for it and it is recommended to use PoolMath?

If it is recommended to use PoolMath, is the Acid Demand Test in the common test kits (like the one my PB gave me) not accurate?

 

[JVTrain]

The acid demand test isn't really necessary. Using your pool values for volume, acid strength, pH, TA and CH (mostly), Pool Math tells you exactly how much acid to add to achieve the desired pH.

 

[Richard320]

The acid demand test is accurate, it's just not really necessary. Poolmath will calculate dosages for you anyway. And as you compare your results to what Effects of Adding Chemicals indicates, you'll soon learn if you're over or under dosing because the pool volume is off.

 

[Jabooh1]

Thanks! I figured a good way to confirm the pool volume is to adjust something and then measure the side effects of it.

I just wondered about the ADT because it is easier than going to the PoolMath sheet.

 

[duraleigh]

I figured a good way to confirm the pool volume is to adjust something and then measure the side effects of it.

Sort of, but not really. Is your pool irregular enough that you cannot do the volume mathematically? I believe calculating pool volume by chemistry dosage is perhaps the least effective method.

 

[Jabooh1]

It is an odd shape.

However i measured flow into a 5 gal bucket so I know the ballpark. ~18,000.

 

[Jabooh1]

FC 6
CC 0
TC 6
Ph 7.8
Ch 625
TA 50
CYA 40
Temp 59
CSI -0.15

I think I am getting the hang of this. However I don't trust my CH and CYA tests. I'm going to test the fill water to see what the CH of it is. Hopefully it is low. We also got some rain today so I hope that will lower the CH.

 

[pwrstrk]

Everything looks pretty good. Your FC is in range for the CYA level. You know your CH is on the high side so keep your PH in check. How stable is your PH ?
On testing your CYA. You can pour the sample back and redo the test a few times to verify you reading. Also did you bring the sample to room temp for your CYA test ?

 

[Jabooh1]

Jeff thanks!!
The ph is getting under control. The plaster is still new (5 weeks old) and I run my waterfall a lot (just like the sound). So if I understand these two things will raise the ph.

I did not bring the water to room temp prior to the cya test. Will redo that tomorrow.

 

[pwrstrk]

Yep the new plaster and the waterfall will raise your PH. If you cut back some on the waterfall that should help with the PH.
Not sure if you saw my comment about your TA. I edited it out as I forgot you had a SWG before I posted. The bottom of the range is 60 for a SWG. I'd leave it alone for now.
Is your SWG running or is it turned off ?

 

[Jabooh1]

Yes I saw the comment on the TA and just figured you didn't see I had the SWCG.

Is there a good rule of thumb for amount of aeration in relation to ph rise? Obviously there will be a lot of factors in play, but other than trying to do multiple test in a non pristine environment (i.e. Only run through waterfall for so many days and measure ph rise) is there anything I can guage by?

 

[pwrstrk]

I'm not aware of any good rule of thumb in relation to the amount of aeration and how fast it would raise PH.
Chemgeek may have a better answer on this.

 

[JasonLion]

No, no good rule of thumb. There are too many variables which don't have any standardized measurement system, and thus no practical way to measure the amount of aeration.

 

[Jabooh1]

I figured. Oh well. Guess I will try to do some testing based on run time and ph increase.

 

[Jabooh1]

Are there any affects of adding MA and Baking Soda together? I added 1/2 gal of MA to drive ph down to 7.4 and 6 lb of BS to raise TA from 40 to almost 70 (did 3/4 or PoolMath total calculated BS). My PH went down as calculated, my volume should be correct (looked at water bill and measured water during fill), but the TA didn't move at all. Stayed at 40.

I'll do a full set of test tomorrow it's 52* outside and too darn cold to get that many samples.

 

[JasonLion]

Adding muriatic acid and baking soda at more or less the same time shouldn't be a problem.

Are you sure you allowed enough time with the pump running, after adding baking soda, for it throughly mix in? An hour should have been plenty.

 

[Jabooh1]

It was on for 3 hours, then I pulled the sample today (roughly 24 hours after the addition).

 

[chem geek]

Remember that the pH scale is logarithmic, not linear. The move from 8.5 to 8.2 will take a lot more acid than the move from 8.2 to 7.9

I would use 8.2 as your start value, use 7.8 as your target, and add enough acid to achieve that move. Wait 30 min and retest. You may need to redo this several times - you know your pH is above 8.2, but it's impossible to know how high above.

The carbonate buffer system is stronger at lower pH as one approaches 6.3 and is stronger at higher pH as one approaches 10.2, but a pH of 8 is in between so the acid to pH movement is roughly linear. With the 60 ppm TA (and 50 ppm CYA and no borates) in the 18,000 gallon pool it takes 1.3 cups of Muriatic Acid to move the pH from 8.5 to 8.2 but it takes 1.2 cups to move the pH from 8.2 to 7.9.

The 0.3 difference in pH units which is a logarithmic scale means roughly a factor of 2 difference in hydrogen ion concentration. If all the hydrogen ion showed up as such, then each doubling of concentration (lowering of pH by 0.3 units) would be twice the absolute amount, but most of the acid added actually goes to converting carbonate ion to bicarbonate ion and bicarbonate ion to carbonic acid (and carbon dioxide). So because of the pH buffering of the carbonates (and cyanuric acid), the pH movement and acid amounts are roughly proportional.