Calcium Hardness Ideal Level

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pool_novice

pool_novice

Member
Jun 3, 2024
18
North Texas
Last week I tested my calcium hardness and the result was 307. I could be mistaken, but I think the Pool Math app told me that level was fine when I entered it. Now it’s a week later and I’ve added some other updated results (TA went down by 20), and the app is telling me the calcium hardness is too low. It is recommending 450 (ideal range 350-550 and safe range up to 650!)

The app recommendation seems quite high when I see other places online recommend for it to be between 200 and 400 for a plaster pool.

What is causing this high CH recommendation and can I trust it?
 

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pool_novice said:
The app recommendation seems quite high when I see other places online recommend for it to be between 200 and 400 for a plaster pool.
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Those places don't account for the high CH fill water in large chunks of the country. Those levels will be near impossible there
 
pool_novice said:
Last week I tested my calcium hardness and the result was 307. I could be mistaken, but I think the Pool Math app told me that level was fine when I entered it. Now it’s a week later and I’ve added some other updated results (TA went down by 20), and the app is telling me the calcium hardness is too low. It is recommending 450 (ideal range 350-550 and safe range up to 650!)

The app recommendation seems quite high when I see other places online recommend for it to be between 200 and 400 for a plaster pool.

What is causing this high CH recommendation and can I trust it?
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You don’t seem to be testing with a kit that TFP believes is reliable. Be careful trusting whatever you’re using that came up with 307ppm
 
Bperry said:
You don’t seem to be testing with a kit that TFP believes is reliable. Be careful trusting whatever you’re using that came up with 307ppm
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The 307 CH came from a pool store test. Everything else in the panel I attached was tested by me using a Taylor kit and new reagents I just ordered from TF Kits.

When I tested CH myself using the Taylor kit a week earlier, I got 370. But it was my first time doing the test and I wasn't sure if I did it correctly, so I input the more recent pool store CH results when I got that a few days later. I'll retest CH using the Taylor kit tomorrow.
 
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pool_novice said:
The 307 CH came from a pool store test. Everything else in the panel I attached was tested by me using a Taylor kit and new reagents I just ordered from TF Kits.

When I tested CH myself using the Taylor kit a week earlier, I got 370. But it was my first time doing the test and I wasn't sure if I did it correctly, so I input the more recent pool store CH results when I got that a few days later. I'll retest CH using the Taylor kit tomorrow.
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Retested using the Taylor kit this morning. CH is either 330 or 340. The color change on this this seems a little more gradual so that last drop is giving me trouble.

Updated results below - I’ll be adding acid shortly.
 

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pool_novice said:
Retested using the Taylor kit this morning. CH is either 330 or 340. The color change on this this seems a little more gradual so that last drop is giving me trouble.

Updated results below - I’ll be adding acid shortly.
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For the CH test keeping adding drops until the color stops changing. If you add a drop and it doesn’t change anything, ignore that drop and record the result. 10ppm either way isn’t a big deal like mentioned above.
 
Newdude said:
Switch to 10ml and each drop is 25 CH. We don't need it zeroed in. 350 or 325 isn't 975. (y)
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Great, will do.

Now back to the original question - the Pool Math app is telling me to aim for 450, or within 350-550. Would you just leave it alone?

It’s getting treated with liquid chlorine and muriatic acid as needed, nothing else being added. When/if it needs to be shocked harder I’ll do that with liquid too (unless somebody here tells me I should use a powder).
 
pool_novice said:
Now back to the original question - the Pool Math app is telling me to aim for 450, or within 350-550. Would you just leave it alone?
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What is your fill water CH ? If its high i would leave it be as it will climb on its own, and quickly.

If its softened water, you'll probably lose CH from rain and I'd bump it a little high to buy more time before needing it again.
 

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Then I'd leave the CH alone and road test how it swings. You can always add some if its dropping, but you can't put the toothpaste back in the tube if its rising.
 
Also, give it time. It'll be quick in the grand scheme of things, but you'll see no daily or weekly change, maybe test it every 2 weeks for now. If its holding well, switch to monthly.
 
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pool_novice said:
Now back to the original question - the Pool Math app is telling me to aim for 450, or within 350-550. Would you just leave it alone?
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In Pool Math on the Overview screen, click into Calcium Hardness. From there, you can change the your Target level. My pool heater recommends staying under 400ppm on Calcium Hardness and so I set my target level to 350ppm. There is a large ideal range and you will need to determine your ideal value.
 
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