Problem Balancing Chemistry of New Plaster Pool

[SoCal_Pool]

Dear TFP,

I just remodeled my in-ground plaster pool and am still within the one month startup period (19 days). The contractor handled the initial startup (3 days) and I been brushing twice daily and handling the chemicals for the last 16 days. I been using Hasa Sani-Clor / HASAChlor (Sodium Hypochlorite) and Hasa Muriatic Acid (Hydrochloric Acid) to balance the FC and pH. I added Natural Chemistry Liquid Swimming Pool Stabilizer and Conditioner to raise the CYA to about 35. I been checking and adjusting the chemistry everyday per the directions supplied by the contractor (National Pool Council Start-up Procedures). Here is the current pool chemistry as of today (Taylor K-2006C):

FC = 2.8
CC = 3.0
pH = 7.7
TA = 80
CH = 240
CYA = 35
Borates = N/A

My current approach is to use liquid chlorine as my primary oxidizer while keeping the CYA level low. But the high alkalinity of the liquid chlorine is making it hard for me to keep my pool balanced.

Here is what I am seeing:

1. Add Liquid Chlorine
2. pH Increases
3. Add Muriatic Acid
4. pH Decreases but
5. Total Alkalinity also decreases
6. Repeat 1 through 5 until Total Alkalinity drops below 80
7. Add Baking Soda to raise Total Alkalinity to within normal range but
8. Total Calcium Hardness increases
9. No easy way to reduce total calcium hardness increase.

CH will continue to climb unless I find a way to break this cycle.

I am having to add baking soda every few days to keep the TA in the normal range so am seeing the CH continue to climb. I realize that CH is well within range at the moment but CH seems to jump at a rate of 20 ppm every time I added baking soda.

Is this normal? Any suggestions?

By the way, prior to the remodel, I had a pool service handle the chemicals but wanted to do it myself since I had a fresh pool to start with.

Thanks…

 

[bdavis466]

Baking soda raises TA and does nothing to CH.

You are probably trying to maintain too low of a pH and too high of a TA. Shoot for 7.8 on the pH and 50-80 TA. pH rise should greatly reduce.

Your CH is rising from your fresh plaster and your fill water. Everytime you add water to the pool the CH will rise.

 

[SoCal_Pool]

Thanks for the reply bdavis466.

Regarding the CH rise, I tested the CH just before adding the Alkalinity UP it was 230 ppm. I added 16 oz of Alkalinity UP, 8 hours later the CH was 250 ppm. The CH had stayed constant at 230 for the previous 14 days. No other chemicals or water was added during this time. I am no expert so have no explanation for this discrepancy. The Alkalinity UP bag says 100% sodium bicarbonate so assume it is identical to baking soda.

I been trying to keep both the pH and TA in the "normal" range every day during the startup period. I was told that even a pH of 7.8 will stain new plaster. Is this true? I am seeing some discoloration of the plaster mostly on the bottom less so on the sides. This started within the first few days of startup (Contractor was responsible)

As my original posting explains, I been struggling to keep my pH within the normal range as it wants to run high. My Taylor K-2006C test kit does not provide an accurate method of measuring pH once it rises above 7.6. The color reference for 7.8 and 8.0 look identical to me. Once the pH rises above 7.6, I am not sure if it is 7.8, 8.0 or even higher.

At this point, I am not sure what the definition of "normal" pool chemistry. From what I was told by my contractor, a TA less than 80 is below normal and can cause damage to the pool plaster. The same could be said of a pH of 7.8 which is above normal per several references. My primary concern at the moment is keeping my new plaster as healthy as possible.

 

[bdavis466]

TA and pH levels are relatively meaningless by themselves. Far more important is the CSI (calcite saturation index) which is a combination of pH, TA, CH, temp, cya, and borates. The CSI of the water tells you if the water is aggressive (etch the plaster) or oversaturated with calcium carbonate (potential to scale). Pool Math calculates CSI for you and it's a good thing that it does because it's a logarithmic equation that takes all of the testing values into consideration.

You really don't want your pH much above 8 because scale becomes likely especially if the TA is also on the higher end of things. pH should also not go below 7 as this will be very aggressive to plaster.

A low TA (50-60) with a higher pH (7.8) will drastically limit pH rise and acid consumption. Use the acid demand test in your kit to help you identify the pH level when it's on the higher side of the testing block.

- - - Updated - - -

The discolorations in the plaster don't have much to do with your chemistry levels. 90% of the time the discolorations are a result of poor workmanship and less than ideal plaster mixtures.

 

[pooldv]

+1 on that. To avoid issues with scaling keep your CSI between -0.3 and 0. Keep your TA around 50-60 and pH 7.6 to 7.8. PoolMath will calculate your CSI number, tweak PH and TA to move the number. More here, Pool School - Calcium Scaling

 

[duraleigh]

At this point, I am not sure what the definition of "normal" pool chemistry.

read "The ABC's of Pool Water Chemistry" up in Pool School. It not only explains the parameters that are important, but gives you "normal" ranges.

Emphasizing what bdavis466 already said, CH and TA are completely unrelated.