Calcium Hardness Plaster pool

CCisotope · May 15, 2014

Pool is finally done and we are now managing the pool water.

These are the results from my test
pH: 7.5
Cl:2.0
FC:4.5
CC:0
TC: 4.5
TA:70
CH: 140
CYA:30

Here are results from about 3wks ago when the CYA was finally giving a read out. Pool was still technically under PB care...though they didn't test the water much nor come out.
Cl:3
pH:7.6
TA:80
CH: 175
CYA: 35

I was concerned about the low CH levels. The readings should be around 250-350 according to the chart and the readings I am getting are pretty low. I did follow the new directions included in the kit and not the directions on the laminated one.

Am I doing something wrong and should I be worried at this point about the Calcium level?

JasonLion · May 15, 2014

If your pool is more than four weeks old you should add CH to get to around 300. If you are still in the first four weeks you should be cautious, as CH will still go up some more.

Durk · May 15, 2014

JasonLion said:
If your pool is more than four weeks old you should add CH to get to around 300. If you are still in the first four weeks you should be cautious, as CH will still go up some more.

Why so high? I am looking at a water report done by Anthony & Sylvan (who built my pool) the second year I had it (2005) where my CH was 290. The A&S computer said ideal was 225-275, said my 290 was too high and I should dilute my pool water (I didn't).

My fill water comes from an unusual well with a CH ~100. I've maintained CH at 225-250 since 2004 and my surface is not as white but feels the same as it did new. Basically, I get it to 250, and then let it degrade until it hits 225 and add back to 250. Otherwise I follow the recommendations on this board, but I figure A&S has the guarantee on my pool and has probably built more plaster pools than anyone else so I follow them on CH. So far, so good.

EDIT: For the record, the recommendation for CYA is 35-200. I stay at 35 to 50.

JasonLion · May 16, 2014

If you have a plaster pool, you need calcium in the water to prevent etching of the plaster surface. The recommended CH level is between 250 and 350. The only time you should keep a plaster pool at lower CH levels than that is when your TA in unavoidably way high.

CCisotope · May 16, 2014

Hubby uses an android app called pool pal and the readout after putting in the numbers from my first post told us to put in:

22 fl oz of bleach (did this)
4.3lbs baking soda (added 4lbs because walmart has the large 4 lb boxes...no time to weigh out .3lbs0
30 lbs Calcium Chloride ( I bought a 25 lb bucket at Leslies last night and added ~10lbs)
2.5 lbs of Dry stabalizer ( we added about 1.5 lbs basically what was left in the 4lb bucket)

Readings this morning was
ph:7.5
Cl: <.3
TA: 90
CH: 250 ppm
CYA:35

I added 242 fl oz of 8.25% Cl this morning. Pool calc said to add 200 fl oz but I had the large 121 oz concentrated 8.25% bleach bottles and it was easier to dump the 2 complete bottles in...again limited time to measure everything out.

Question: Should I add another 5 lbs of Calcium Chloride to bring the CH values up a little higher or are we okay for now? I know the lower limit is 250 and its been about 5 1/2 wks since the pool was filled. Since this is a new pool will the Ca levels continue to fluctuate or will they hold steady for the rest of the swim season? Once the levels are within range can I get away with testing the CH level 2-3 times a swim year?

Thanks

duraleigh · May 16, 2014

CH will either stay level or increase somewhat over the season. 2-4 times testing during the season is sufficient for CH.

CCisotope · May 16, 2014

So I don't need to add another 5lbs of Calcium Chloride to bring the CH value up and water is pretty balanced at this point? (except for the Cl which I am assuming was affected by the CYA that was added last night.)

How much higher will the CH level rise over the season? Just don't want any Ca to be pulled out from the plaster over the season to ensure the longevity of the pool finish.

I've been the pool girl since the pool was finished and hubby is leaving most of the pool care in my hands. I just want to make sure the water is balanced and I'm doing everything correctly.

Durk · May 16, 2014

JasonLion said:
If you have a plaster pool, you need calcium in the water to prevent etching of the plaster surface. The recommended CH level is between 250 and 350. The only time you should keep a plaster pool at lower CH levels than that is when your TA in unavoidably way high.

I know this. I am trying to understand why the recommendation, as it is in conflict with the largest PB in the US. My current chem numbers are:

FC=5
TC=5
pH=7.8
TA=60
CYA=35
CH=225
Temp=65°

Chlorine is LC. I run a low TA because in ten years on this pool I know I can keep a 7.7-7.8 pH with a TA of 50-60 and never add a drop of acid.

This brilliant program I use called PoolMath (you may have heard of it) says this is a CSI of -0.15 and will go to -0.06 as the water warms to 75° which it will do if the sun ever shines again in NJ. Are these levels antagonistic to my plaster?

I'm not arguing here, I'm just trying to understand something that doesn't make sense to me. I have a world of respect for your expertise. I know I am different than most, as I have to fight to keep enough Ca in my pool, while most seem to be fighting to bring it down.

Also, I, like most in this past brutal winter, used the bulk of my stock of Dowflake for icemelt and I was never able to restock. What did come in was Canadian magnesium chloride. I probably won't see Dowflake until next winter, so new CaCl will come from the pool store at their outrageous price.