Calcium is 800 Should I be Concerned?

[HouTex]

Just tested calcium again with my TF-100 and I got 800. Here are my complete results. The pool calculator says that the saturation index is .16 which is balanced. But should I be concerned about the calcium? By the way, two pool stores put it closer to 300.

FC 7 (still adjusting the SWG for the Texas summer)
CC 0
TA 100
pH 7.5-7.8
CA 800
CYA 60
Salt 3600
Borates 80
Temp 89

Even though the pool calculator says that the water is balanced, could this be causing the roundish splotches in the Luna Quartz I described in another thread?

 

[257WbyMag]

I would be somewhat concerned about that high of a CH. And on your pH, which is it? 7.5 or 7.8?

At 7.8, your CSI is pretty close to problematic at 0.44. You are going to need to make a concerted effort to keep that pH low, as close to 7.2 as you can. You might consider changing out some water as well. Lowering your TA couldn't hurt either.

There are some folks such as those who live in the desert SW who have to find creative ways around high CH levels such as the 800 that you have. it is not impossible to deal with. It just takes some special attention.

 

[JasonLion]

High calcium levels can be lived with if you manage them closely. If your fill water CH level is high and you have a lot of evaporation you often have no choice but to live with fairly high CH levels. You need to compensate for the high CH level by keeping PH and TA relatively low. With CH at 800 you certainly want to bring TA down to around 60 to 70 sometime soon.

 

[HouTex]

I put 7.5-7.8 as the pH because it appears to be between the two colors on the kit. I assumed it was 7.6 and plugged that into the pool calculator and got .16 for the saturation index. My pH is still rising constantly. I'm adding about a gallon of MA each week--1/2 gallon every 3-4 days. So my pH is going from say 8.0 down to around 7.2 after I add the MA.

In any event, why should I be concerned if at 7.6 pH the pool calculator says my saturation index is .16?

 

[JamesW]

You might have test interference from metal ions. You should retest the calcium by doing the modified test. See the post by JasonLion regarding extended test instructions.

The sample may turn purple during the test, or go to blue for a moment and then turn back to red/pink. This is called a "fading endpoint" and is caused by interference from metal ions. If this happens, do the test again, but this time add five drops of R-0012 before adding any R-0010 or R-0011L. Remember to count the initial five drops in the total.
In extreme cases, a fading endpoint may occur even when adding five drops of R-0012 at the start. If that happens, mix pool water with an equal quantity of distilled water, test that, and then multiply the result by two.
post206396.html

 

[duraleigh]

In any event, why should I be concerned if at 7.6 pH the pool calculator says my saturation index is .16?

Experience teaches us all that to rely on cold hard numbers is misleading.

Having a pH that high and having a TA that high and having a CH that high is a problem. The csi is an indicator of a potential problem but it doesn't promise there will be a problem nor does it guarantee there wont.

Relying solely on CSI ( I personally don't ever consider it because I keep my pool within normal parameters as much as possible) is akin to relying solely on an IQ test to determine if someone will make a good doctor.

 

[JamesW]

In any event, why should I be concerned if at 7.6 pH the pool calculator says my saturation index is .16?

Using the following numbers that you provided:

pH = 7.6
TA = 100
Calcium = 800
Cyanuric acid = 60
Salt = 3600
Borate = 80
Temperature = 89 ^oF

I get a CSI of +0.29

 

[Richard320]

Yes.

You're at serious risk of scaling. I've been there, done that, still dealing with it. If you're at 800 now, you'll be at 1100 in a month. There will come a point when no matter how much you mess with pH and TA, you won't be able to stop it.

I didn't have the luxury of a drain last year due to water restrictions. I still don't feel like starting from scratch with my water balance. So I use pool water to water my lawns, then refill the pool. It's a nuisance, but CH needs to be kept in check somehow! Rainwater is the best, zero calcium.

 

[zea3]

Make sure the calcium test is being conducted correctly before you change anything. Do you have a speed stir? If not it is very important that you swirl the test sample constantly and for the prescribed length of time before adding each drop. If the test is not conducted correctly you may have an artificially high result.

I am assuming from your user name you are in the Houston area? Houston is not known for exceptionally hard water. Test your fill water calcium level. If it is low that can also indicate testing error on the pool sample. Finally, if you have been adding calcium hypochlorite products to the pool that could drive up the calcium level. I don't think new plaster leads to high calcium unless the water is out of balance and leaching calcium from the pool.

 

[HouTex]

I just tested my fill water and it showed 150. We've had very little rain here in Houston and I add about 1/2" of water every 2-3 days due to evaporation. I suppose that's the reason for my high CA. But I will note that the last two pool store tests (at different stores) show the CA level to be 320 and 340 (this was about two weeks ago). I'm not 100% confident that my test is accurate--but I'm swirling the h__l out of it.

[edit] I have not been using cal-hypo products. Only a few pucks early on and then a SWG. My pool is about 6 months old.

 

[zea3]

I would be inclined to say your result is a testing error. How long did it take to jump from around 300 to 800? A half inch of water every couple of days would not account for that much of a rise in CA. To be on the safe side, keep the TA around 70 and the pH around 7.2 so you don't develop scale.

Also, try this final test method I pulled from the previous post by James W.
In extreme cases, a fading endpoint may occur even when adding five drops of R-0012 at the start. If that happens, mix pool water with an equal quantity of distilled water, test that, and then multiply the result by two.
post206396.html

That will tell you if the original 800 result was an error without using up all your reagent.

 

[chem geek]

The csi is an indicator of a potential problem but it doesn't promise there will be a problem nor does it guarantee there wont.

Assuming that measured numbers are accurate, then a negative or zero saturation index does indicate that the formation of calcium carbonate scale is impossible (i.e. it does guarantee that there won't be more scale). A negative saturation index says that dissolving of scale or plaster is possible, but not whether it will actually occur. A positive saturation index says that formation of calcium carbonate scale is possible, but not whether it will actually occur. For the original numbers in this thread, the saturation index (using my spreadsheet) is from +0.14 to +0.35 depending on the pH of 7.5 to 7.8. The Calcium Carbonate Precipitation Potential is from 8.0 to 22.9 (again from a pH of 7.5 to 7.8) and represents the maximum possible amount of scale that could form in ppm of calcium carbonate. These amounts are on the high side because of the strong pH buffering from the high borates level.

Of course, right now we don't know whether the actual Calcium Hardness (CH) number is 800 ppm or 300 ppm and that obviously makes a big difference. If the CH is 300 ppm, then formation of new or additional scale is not possible.

 

[HouTex]

My plaster installer came out and inspected my pool. Here is his response:

"I went by yesterday to check on the plaster. Here are the chemical readings that I came up with.

FC 4.5-5.0
P.h. 8.0
TA 80-90
CYA 60
CA 570

With these readings especially the CA at 570 is has your water at a very aggressive state and is etching your plaster. The only way to drop your CA is to drain the water and add fresh water. To repair the damage that has been done we will need to do a no drain acid wash 1st then drain the pool pressure wash and refill the pool. The cost for this work is $500.00. Let me know if you have any questions. Have a nice day."

First question is whether he is right. I thought the high pH could cause scaling, but can it etch my plaster?

I had the water tested by the pool store this past weekend and they got 400. I saw the person do it twice and she used the same Taylor reagents I use in my TF-100 kit and she did it right. She also had the auto stirrer.

I also think the plaster guy's pH test is a little high. I added 1/2 gallon of MA Saturday and I've been watching my pH every day. It was at 7.2 on Sunday evening and yesterday it was at 7.5 and today it was up to 7.8 according to my TF-100. I was planning to add another 1/2 gallon of MA tomorrow morning, but I'll add it tonight.

I really don't want to do a water drain, etc. for $500. The plaster does not look that bad. My wife, who is extremely picky, does not mind the look of the plaster. Any suggestions other than keeping my pH below 7.5?

My main concern is about the CA level. We've only had 2 or 3 good rains here in Houston since we built the pool in December 2010. Unless we get rain more often it seems I'm destined to do a half drain every 4 months or so.

 

[JasonLion]

There is something wrong with what they told you. Your calcium saturation is dangerously high, not dangerously low. You are at risk for calcium scaling, not etching. However, their proposed solution is correct for calcium scaling. So it is all kind of mixed up.

As mentioned earlier you can prevent calcium scaling, or at least any new calcium scaling, by keeping the PH and TA levels down.

Check around in your area and see if anyone offers reverse osmosis treatments. That can lower your CH level dramatically without replacing any significant amount of water, though it does cost something.

 

[HouTex]

Thanks. But water is so cheap here (although I hate to waste it) that it's probably not worth it to do RO. I didn't even notice the increased water bill when I filled my pool last December. It sounds like I need to replace about half of my water and really be careful to keep my pH below 7.5. The bad part is that I really liked the way my water looked and felt. It sucks to have to redo the salt, borates MA, etc.

 

[HouTex]

UPDATE:

I started to replace my water today and as the water drained the mottling in the pool revealed itself as scaling. It turned white as it drained and when I sprayed a 50-50 mix of MA and water the white stuff fizzed and melted away. After about 30 seconds or so I rinsed it and a perfect layer of French Gray Luna Quartz was revealed.

So my question is what do I do now? I plan to drain about 70% of my water and replace it with new water that has high TA (about 220 IIRC) and 150 CH. I've been feeding my pool MA like it's an addict, going through about a gallon each week since the start up period (and I used about a 1/2 gallon each day during the start up period). My pH ranges from 8.2 (only for a day at most and likely closer to 12 hours) to 7.2 after I add the acid. Lately, I've started to add the acid more often and in lesser amounts to prevent the pH from getting to 8.2 or even staying at 7.8 for very long.

So should I make sure my pH never gets to 8.2 and my CH stays below say 400? I've pretty religiously followed the CSI and to be honest it didn't work out that well. If you average out my constantly rising pH I was not supposed to be at risk of scaling--but that's what I got (although it's not horrible). If the lesson is that even 12 hours or so at 8.2 pH causes scaling then I will be even more careful in not letting pH get above 7.8--even for short periods.

Any suggestions on how to avoid additional scaling would be appreciated. I know the drought here in Houston is not helping matters.

 

[ROB N]

Yes, be concerned. Worry about keeping the ph in check and the csi will be a non issue. MA is cheap and not hard to add to maintain a low ph. On the other hand calcium scale is very difficult to remove and to do a drain and acid wash would be expensive and an avoidable hassle. As opposed to a few minutes of your time to test and add a few cups of MA each day. IMHO

 

[HouTex]

That's what I've been doing. I test my pH at least every other day and sometimes each day and I watch it go from 7.2 after I add acid up to the 7.8 to 8.2 level when I add acid again to bring it down to 7.2 and the process repeats itself. It's not at 7.8 to 8.2 for very long. I guess I need to make sure it never goes above 7.5. I will probably have to add acid every day (in smaller amounts) or maybe every other day vs. every 3-4 days in larger amounts.

 

[ROB N]

That's what I've been doing. I test my pH at least every other day and sometimes each day and I watch it go from 7.2 after I add acid up to the 7.8 to 8.2 level when I add acid again to bring it down to 7.2 and the process repeats itself. It's not at 7.8 to 8.2 for very long. I guess I need to make sure it never goes above 7.5. I will probably have to add acid every day (in smaller amounts) or maybe every other day vs. every 3-4 days in larger amounts.

just a few minutes a day and you will be able to keep on top of it!