Where is my CH coming from?

[IsaacFL]

About a year ago I drained the pool and had the tile blasted, because of high CH and scaling left over from the prior owner. My fill CH is about 175. Int the last month my CH has jumped from 575 to 700. According to Poolmath with my 6640 gal pool that is equal to adding almost 7.75 lbs of Calcium Chloride just in the past month?

I don't think it is coming from the fill water, since I know from my water bill that evaporation hasn't really been an issue yet.

The only thing that has changed, is in the last month my pool is now in the sun, and had to increase the salt cell to compensate and also I am having to add acid at about 12 oz every 4 days to keep pH in balance. Water temp has also increased from about 74 to 88 in the past month.

Here are my test results since the day of drain and refill:

Date Calcium
6/12/2016 700
5/6/2016 575
4/24/2016 575
4/15/2016 550
3/24/2016 525
2/28/2016 525
1/20/2016 500
12/30/2015 500
11/15/2015 425
10/10/2015 425
9/21/2015 425
9/5/2015 400
8/25/2015 400
7/22/2015 310
7/14/2015 300
6/23/2015 250
6/20/2015 250
6/11/2015 225
6/7/2015 225
6/1/2015 200
5/25/2015 200
5/23/2015 200
5/12/2015 175

 

[IsaacFL]

Don't know if it is relevant but before I drained and refilled the pool the CH had been steady at around 1050 for the prior 3-4 months after we moved in.

 

[LisaDLu]

IssacFL - I feel your pain! My CH has steadily climbed over the past year and now I am over 1000. We are having Roadrunner Pools come out tomorrow to do a reverse osmosis to get the CH down (I am down the street from you in Palm Desert). I have been around and around on this forum trying to figure out why my CH climbs but none of the suggestions have been valid in my case.

One of the guys who came out to give me a quote for RO did tell me his tests showed I had high TDS and conductivity, and that coupled with my low TA (which I was keeping at 60 as recommended here for salt water pools) was making my water corrosive and pulling calcium out of the plaster. After I get my water filtered I am going to keep my TA higher at 80 or more.

 

[jblizzle]

It is at least paritall from the fill water and evaporation. Mine goes up roughly 150ppm per year.

Here is an old thread that is very related to your questions. Looks like some of the links are broken unfortunately. This says a 300ppm yearly rise would not be unreasonable. But yours seem excessively higher than that. How do you maintain your chemistry?
Changing saltwater pool water every 2 years?

- - - Updated - - -

One of the guys who came out to give me a quote for RO did tell me his tests showed I had high TDS and conductivity, and that coupled with my low TA (which I was keeping at 60 as recommended here for salt water pools) was making my water corrosive and pulling calcium out of the plaster. After I get my water filtered I am going to keep my TA higher at 80 or more.

It is not true that just a low TA would result in calcium pulled out of the plaster. You have to look at your CSI. Maintaining a higher TA with a SWG will just mean your pH will rise faster and require you to add more acid to lower it.

 

[pooldv]

Post your last couple of full test results. Do you monitor CSI? If so, how has that trended?

 

[IsaacFL]

Post your last couple of full test results. Do you monitor CSI? If so, how has that trended?

Test Results on 6/12:
FC 5
CC 0
pH 7.8
TA 70
CH 700
CYA about 70.
Salt is at 3760.

Test Results on 6/11
FC 5
CC 0
pH 7.6

Test Results on 6/10
FC 4 bumped up cell production
CC 0
pH 8
R 5 1 drop pH 7.7
2 drop pH 7.4
-> added 12 oz acid


I monitor the CSI on the Poolmath Page religiously. It depends on temperature, but right now my water temp is 90, so right now I have to watch pH more.

 

[pooldv]

Well, that all looks good. I don't know, sure seems odd. Hopefully, someone will see this with a better idea.

 

[jblizzle]

Well, that is fine for the last 3 days, but what has the trend been over the last year? Are you saying that your CSI was never very negative?

 

[IsaacFL]

Well, that is fine for the last 3 days, but what has the trend been over the last year? Are you saying that your CSI was never very negative?

It is never negative to the point of being out of balance on the acidic side. My pH constantly goes up and then I have to add acid to bring it back in balance. The most negative was in the winter when the water temperature was around 50-60, but it was always just in balance. I just didn't add as much acid then.

I constantly use PoolMath and enter current temperature etc, so I know where it should be before I add acid and how much.