can't get calcium above 175 ppm

[red7272]

Hi,

I have a new pool with poolcrete plaster. The manufacture recommends a calcium level of 300 to 400 ppm. I added a huge amount of calcium chloride and the calcium level seems to stop at 175 ppm (enough to raise it over 300 ppm). As I add more calcium chloride it seems to all just go to the bottom of the pool and the ppm does not go up. I have a Taylor test kit and had a local lab test. After a week a vacuums the white layer off the bottom of the pool and sent it to waste. Is it possible that the water could be saturated with calcium?

Water is from a borehole (original lab results attached). Since the report I have only added the calcium, chlorine and acid. The calcium is within an acceptable range and the pH has always been on the high side -- struggling to get it down.

Any thought or suggestions would be most appreciated.

Thank you,
Patrick

 

[Bama Rambler]

Sounds like something else in there besides calcium. Calcium chloride should have dissolved in a few hours at most. What's your water temp?

 

[red7272]

Thank you for the quick reply. The pool is 70 to 75 degrees. I am in Africa so there is always a question about the quality of things you buy. I bought the calcium chloride from a reputable supplier so I assume it is good. It did manage to raise the ppm from 55 to 175 so it did something.

 

[Bama Rambler]

Which test are you using to determine the CH?

 

[onBalance]

Chemical labs often list their tests for ppm of "calcium" different than how the pool industry does and our pool test kits do. The 55 ppm of calcium (obtained by the lab) needs to be multiplied by 2.5 to convert to "calcium carbonate" and to obtain the appropriate "calcium hardness" number, which actually makes it "137 ppm", not 55 ppm. Note that the "total hardness" (which includes magnesium also) and total alkalanity is expressed as CaCO3 (calcium carbonate), which is how our tests kits calculate the amounts. If your chemical lab is testing the calcium and obtaining 175 ppm now, then the actual or correct figure is 437.5 ppm of "calcium hardness" expressed as calcium carbonate, which corresponds to our way of testing.

The total alkalinity is extremely high, so that needs to be verified and lowered if it is actually 700 ppm.

 

[red7272]

I am using Taylor Technologies K-1770 Drop Test, Hardness-Calcium I bought off Amazon.com (see here). I also had the local water authority run the test -- not sure how they do it.

 

[onBalance]

If the alkalinity is really that high (700 ppm), then it was it is likely that the pH was higher than 8.5 when you added the calcium chloride. If so, that is why it seems that the calcium chloride went straight to the bottom of the pool. Adding calcium chloride when the pH is very high, (over 8.5) will cause a precipitation of calcium (carbonate) to occur, and it will just go to the bottom and get filtered out, and not raise the calcium level.

Also, if the TA is that high, then there is no need to raise the calcium level, since the CSI is already higher than it should be.

 

[red7272]

Thank you very much for the help!! I cannot get any good advice in Tanzania so I really appreciate the help. I also have limited chemical options here so please let me know if the following sounds reasonable:

1) I will continue to add pH minus to get the pH down. I have almost done this in the last couple of days. This should also bring the alkalinity down. Is that correct? I do not know of anything I can buy here to bring down the alkalinity. Do I need something separate for the alkalinity? The chlorine is in the acceptable level.
2) I will then add stabilizer -- I have not done that yet.
3) Once the alkalinity is lowered, I will then be able to add more calcium chloride to raise the calcium level above 300.
4) I have a chlorinator but have not yet added the salt or turned it on. Once the pH, alkalinity and calcium are the acceptable range I will then add the salt and turn on the chlorinator.

Does the sound like an acceptable course of action? The pool newbie in Africa appreciates the help!

Thank you again.
Best,
Patrick

 

[Stuamurr]

Reading the screenshot, it says borehole, so I make the presumption that this is your fill water results, and not your pool water results.

Do you have the ability to test for Calcium Hardness and Total Alkalinity with your own test kit?

Acid will bring your TA and pH down, read this article for more information pool-school/lowering%20total%20alkalinity

I think your plan to sort out Alkalinity is sound enough, Total Alkalinity is usually my first port of call when I start a new pool, I usually find getting the alkalinity level correct makes everything much easier, although I am usually going to opposite direction with Scottish Soft Water supply.

Regards
Stuart

 

[onBalance]

The pH minus product is an acid, and it lowers both the pH and the alkalinity. You should add stabilizer now, and of course, keep adding chlorine. You are on the right track. And never add calcium chloride when the pH is above 8.0, and only add when the pH is below 8.0.

 

[red7272]

Thank you for everyone's help! I finally got both the pH and Alkalinity down to the normal range.
Best,
Patrick