Calcium Hardness

[tsyemma]

Just opened a newly installed pool the first week of February 2014. Started using the test kit provided by the pool builder but it only tested for Chlorine/PH/Alkalinity. Purchased a new kit which also tested for CH & CYA. However, I questioned the results of the testing using this pool kit. I suspected the testing for certain chemicals was incorrect specifically CH & CYA. I then purchased the Taylor K-2006 and confirmed inaccuracies. However, as soon as I started using this kit, the CH test was in the 550 ppm range. I knew this was high. So, I drained about half the pool and added fresh water. I used water from a source inside the house which is less than 10 ppm CH. (I have a water softener). However, I also tested the outside spigot (which originally filled the pool) and that reads at 150 ppm. My pool CH is now at 340 ppm. The problem is during the drain/refill process the tile was exposed & dried and I had what I believe is scale. Lucky for me, I caught it early and it comes off easy. However, I still have a few questions:

1. Could scale have built up that quickly with high CH (3 month time-frame) - Its important to note my PH was kept in the 7.5/7.6 range and never exceeded 7.8 during this period. In addition, I kept my alkalinity b/w 60-70

2. Is it possible the "scale" is actually salt residue from evaporation. I have a SWG.

3. What would have caused the pool CH to rise to 550 ppm if it was filled with 150 ppm. Could it be the new plaster?

In addition, I try to keep my chemical balance as recommended by TFP for salt pools. In fact, TFP recommendations closely match what my builder recommended. If it were not for the bad CH readings to begin, I would be issue free. The pool is otherwise crystal clear and all the numbers now in balance.

 

[JasonLion]

Welcome to TFP!

1) Could: sure, scale can develop in days under the correct conditions. But if your PH claim is correct it shouldn't have had any scaling.
2) Salt and calcium deposit just above the water line because of evaporation in most pools. This happens a lot more quickly when CH is too high.
3) Yep, new plaster. New plaster will raise PH, TA, and CH levels quickly for the first month, and more slowly for up to a year. Also, calcium doesn't evaporate, so any time you top off the pool you are adding more calcium, which raises the level.

 

[tsyemma]

Yes, excellent site. Glad to be a member. For your answer to #2 above, that is exactly what happened. The scale is above the line. Any recommendations to keep this in check. Also, for #3, if I am topping off with water that is 150 ppm. Should this not effectively lower CH?

Any other recommendations for this problem?

 

[JasonLion]

You lose water through evaporation, but you do not lose any calcium due to evaporation. All the calcium that was there is still there, even through the water level went down. When you top off with more water, it contains yet more calcium, so the calcium level just goes up and up over time.

You can only lower the calcium level if you remove water (along with it's calcium). Evaporation doesn't do that.

Keeping PH and TA fairly low and CH under control will help minimize calcium/salt depositing on the tile, but nothing will stop it completely.