Fountains, CH, and low CSI

[JamieP]

I'm wondering if I need to add some Calcium to the pool to try to bring my CSI up a bit?

Here are my current numbers:
FC= 9.0
CC= 0
PH= 7.7
TA= 70
CH= 275
CYA= 80
Salt= 3600
Temp= between 84-92 depending on time of day, and evaporative cooling from my fountain

We have been running our homemade fountain to bring down the pool temps. It works, but it raises the PH, making me have to add more acid. When I bring the PH down to 7.2 in anticipation of it rising again from the aeration, the CSI goes waaay low. Even at 7.5 the CSI is out of range. Also, the TA is coming down because of it and may be closer to 60 now. I got 70 when I checked it a week ago.

In pool math I see that a higher PH and higher CH will help the CSI come up. Should I add more calcium to the pool? I've been topping off the pool to account for the evaporation, but so far I haven't seen a significant increase in the CH. What would you recommend?

 

[duraleigh]

I would never suggest to add CH to a pool just to satisfy CSI. Thousands of pool owners here NEVER calculated CSI and have perfectly good pool water.

What is the CH of your fill water?

 

[atttech-2]

If your fill water has not been bringing it up by any appreciable amount I would raise it to 350 or so to be more inline with suggested range.

 

[atttech-2]

I will admit I don't look at my CSI level often but you are on the lower end of the recommended CH for plaster and since your pool is new I think it would be a good idea to bump it up so it does not try to take it out of the plaster. If your fill water was high with all the evaporation you are getting from heat and the fountain it would have come up on its own fairly quickly but it sounds like that is not the case.

 

[JamieP]

Way back in the beginning (March) I tested the CH of the fill water at 175 but I should test it again. I'll do that today when I get a moment.

I wasn't really concerned since I had been told my CH would rise gradually over time and that I didn't need to help it along since it would eventually get harder to manage with my hot climate, but I recently read a thread about pitting of plaster and it made me think. I have a couple of divots (or pits?) in my shallow end that I attributed to uneven plaster application or to overzealous brushing at startup (the plastic of the brush dragging on the floor.) But with my CSI being low I began to wonder if that might be the cause. Or would pitting be more uniform?

 

[pooldv]

The pitting will be gradual and sporadic. As plaster dissolves it will release pebbles from the surface. There is no downside to adding some CH to your pool. Our water in Dallas is difficult because it has high scale potential normally but in years where it rains a lot in the spring the CH drops low in the lakes and the trend reverses to high etching potential. I have some etching in my pool from the first year. As I was studying up on CSI, scale and etching I went back through my records recently and calculated CSI and it was well below -0.6. That first year, 2012, my CH was 150-160. By 2014, well in to drought, my CH climbed to 450. With all the rain last spring and this spring my CH had dropped back to 290. It felt like my etching was getting worse so I added CH to raise it back to 350.

 

[duraleigh]

So, just a reminder that TFP suggests a CH level from 250-400.

You do not "lose" CH. It stays in your pool and accumulates unless you do a direct replacement with water that is lower than the CH of your pool. Refill water does not count.

If it were my pool. I would not consider adding calcium. The chance of you having erosion of plaster from aggressive water (with your conditions) approaches zero.

That said, you seem rather determined that you need some. I have read too many stories of problematic high CH to recommend it.

Kept within 250-400 CH will not be a problem. You seem to test regularly so you will notice any trend up or down. Keep an eye on it no matter what you decide.

 

[JamieP]

Thanks everyone. I just retested my fill water and got a CH of 100. That's well below the 175 from March (which might have been testing error as I was very new at all of this back then.). But it would explain why my CH hasn't been rising as much as I expected it would.

One question about the CH test.... My R-0011L blue dye produces very small drops (compared to other tests), and I'm always left with a residual drop I have to wipe off the tip when I'm done or it will leave a mess. Is this normal? If not, how would it affect my test results?

 

[JamieP]

The pitting will be gradual and sporadic. As plaster dissolves it will release pebbles from the surface. There is no downside to adding some CH to your pool. Our water in Dallas is difficult because it has high scale potential normally but in years where it rains a lot in the spring the CH drops low in the lakes and the trend reverses to high etching potential. I have some etching in my pool from the first year. As I was studying up on CSI, scale and etching I went back through my records recently and calculated CSI and it was well below -0.6. That first year, 2012, my CH was 150-160. By 2014, well in to drought, my CH climbed to 450. With all the rain last spring and this spring my CH had dropped back to 290. It felt like my etching was getting worse so I added CH to raise it back to 350.

Thanks Pooldv. Your experience is helpful. I found particularly interesting your assessment of the affects of our seasonal rains on the CH of our water supply. I wonder if that might be related to my new result for the CH of my fill water?

I still need to decide what to do about adding calcium. I'm leaning towards adding some, but I'll probably think about it for a bit.

 

[duraleigh]

Thanks everyone. I just retested my fill water and got a CH of 100. That's well below the 175 from March (which might have been testing error as I was very new at all of this back then.). But it would explain why my CH hasn't been rising as much as I expected it would.

One question about the CH test.... My R-0011L blue dye produces very small drops (compared to other tests), and I'm always left with a residual drop I have to wipe off the tip when I'm done or it will leave a mess. Is this normal? If not, how would it affect my test results?

That fill water CH is VERY low. That said, your CH will naturally increase over a long period of time.

The small R-0011L drops are normal. The specific gravity of that solution is greater than the others, I think, so it falls off the dropper tip more quickly. It doesn't really matter, you are simply trying to get enough dye into the mix so you can see the color change. You could probably get the same thing with 4 drops or 6 drops but stick with the five....we know it works. I dry off the tip every time with R-0011L.......it is messy.

 

[pooldv]

That is very low CH, the 2014 water report showed 110 ppm. So, your water supply seems to be a bit lower on CH than Dallas. I would add some CH up to 250 ppm. There is nothing to lose. Your CH creep is likely to be low with low CH fill water. So, it isn't going to jump up to 400+ very quickly. And if it does you have low CH fill water to replace some.