Super high CH! Need to fix it and remove scaling


New member
Jul 8, 2020
Sacramento area
Hi, I think this is my first time posting here, although I have read a lot of posts over the years. Learned a lot, but still a lot I don't know.

I have a gunite pool (around 16K gallons) that is about two years old now. I do my own testing with one of the Taylor kits and have generally been good about watching the PH and FC levels. A bit spotty on the CYA and TA levels and rarely tested for CH. Well, now my CH has hit 960 and seems like it may still be climbing. I decided to drain some water out and refill to deal with it only to discover I have a calcium buildup ring on the tile all around the pool at the water level. I hadn't noticed it before because we have an automatic water filling device to compensate for water loss so now the water level doesn't really change at all. I am hoping to get ideas about how to best bring down my CH and also remove this buildup.

The current water readings are:
FC=1.2. (I usually shoot for 5-9 using Cal Hypo powder in 24 oz increments depending on how much use the pool got, temp, and if any algae is present. Didn't add Cal Hypo this time because am draining some water .)
PH=7.6. (My water has a naturally high PH - over 8 - and I am constantly battling the rise. I use muriatic acid (31%) in 26 oz amounts to bring it down.)
CYA=around 33. (This used to always be closer to 50 and 60, but has recently come down to the 30-40 range. I did have a period of time very recently where it was actually at 0 and I realized I had forgotten to check on the trichlor tablets I often use in the dispenser. Adding two seems to have solved that problem.)
TA=Around 85. Initially, this was in the 120s or so, but has been falling somewhat steadily over time. I recently got a reading of 40, but that could have been a mistake on my part, I suppose.
CH= 960! This used to be much lower at around the mid to high 300s, but apparently has risen quite a bit over the last two years. Unfortunately, I was not worried about this given the initial readings and never seeing signs of buildup so I hardly ever measured it. It was around 750 a year ago. Too bad I didn't realize that was a problem.

My average pool temps during the day right now are in the high 80s and sometimes low 90s (we have solar heating). After a couple hot days and especially if the kids use the pool a lot, my FC plummets and I have to add a lot of Cal Hypo. Sometimes I am slow to do so and start to see a little algae building up on the pool walls. Scrubbing it and adding the chlorine deals with it easily enough. My water is almost always crystal clear. We also have sheer descents so it can get a lot of aeration.

But, is using Cal Hypo a mistake at this point? Should I be switching to non-chlorine based oxidizer? Also, how much water should I attempt to replace? I am draining it right now via a garden hose and pool pump, but it is pretty slow going and I don't know how to turn off the automatic water filler either. A little concerned about the sun beating down on the gunite if water is drained below tile level (I live in the Sacramento area so temps are in 90s much of the time).

Separately, I have read that if my calcium buildup is the carbonate kind it isn't too hard to remove, but if is the silicate type, it is a real pain. I don't quite know what I have because I tried to test it with muriatic acid to see if it would foam, but while it did foam a tiny bit on the grout, it didn't on the tile. However, that could be due to there not being much actual material buildup on the tile since I can't even feel it with my finger - it's just ugly. Is pumice stone really the only way to try and remove it? Are there some chemicals I should try? Is muriatic acid a good way to do this without damaging the tile? I am attaching a picture of the buildup.

Lots of questions, I know, so I apologize. Thanks, in advance, for any help!


  • Calcium buildup.jpg
    Calcium buildup.jpg
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Gold Supporter
Bronze Supporter
Jun 11, 2018
Verona, MO
An expert should chime in soon.
I believe the Cal in Cal-Hypo stands for Calcium...

Use liquid chlorine to raise your FC.
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Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
Jun 22, 2014
Texas, San Antonio/Marion, South-Central Area
Pool Size
Salt Water Generator
SWG Type
CircuPool RJ-45 Plus
Welcome to TFP! :wave: Yes, the cal-hypo is related to your elevated CH level and scale problem along with allowing the pH to rise over 8.0. Those two things alone twill drive up your "CSI" level (see PoolMath) and cause scaling. So what now?

1. Exchange some water. That's the best way to lower the CH level. See link below. I don't think you have a high water table to worry about, but you also don't want to leave the plaster exposed to summer heat for too long either.
2. Once that's done, post a full set of water results back here for us to review. We'll coach you from there
3. Find a place that sells liquid chlorine. I believe CA has some places that sell in bulk and/or where you can use refillable containers. But for now, check Home Depot or Walmart for their pool chlorine. Regular bleach will work as well. No more cal-hypo.
4. Read our ABCs of Pool Water Chemistry and those Vital Links below in my signature. Those are very important and you'll use those references often. If you invest just a little time to understand those references, your water will be in great shape.

Let us know if you have any questions.



Silver Supporter
Jul 29, 2018
"Old" Katy, TX
Pool Size
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
Since it seems you haven't used liquid chlorine, a couple of helpful hints. One-don't buy bleach with additives, fragrances, anti-splash, etc. Pure sodium hypochlorite and water. Also notice the percent of chlorine in the product. It can range from 6% to 12.5% (if you see no % on the label...just "concentrated", that means 6%). Clearly you need to do some math to compare prices. Here in the Houston area, for example, Walmart has the lowest price until you adjust for percent. Walmart 10%. Leslies 12.5%. Leslies has 25% more chlorine per gallon of product., so after taking that into account, Leslies is cheaper (plus you don't have to go to Walmart.) Also here in Houston, Home Depot and Lowes are more expensive than Walmart or Leslies. Your locale may be different. The company that provides chlorine to Leslies is in California, so their prices may be better. Just know how much chlorine you're buying when you compare prices.

Rancho Cost-a-Lotta

Silver Supporter
Apr 10, 2018
Rancho Cucamonga, CA
Pool Size
Salt Water Generator
SWG Type
CircuPool RJ-45
Waterline scale is a challenge to remove. If the chemical and manual methods fail, consider media blasting. In my area, costs are about $4 per liner foot. I did this last year to give me a clean start. Here's my post with some great advice and info from @JoyfulNoise:

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