Low Ch

[AZAA]

My K-2006 Taylor test kit tells me my Ch is 180 (checked yesterday and again today). I live in the Phoenix area which has notoriously hard water.
Pool Math suggests adding 35lbs of calcium chloride to raise my approximately 13000 gallon pool to the correct level. All other chemicals are within range. 35lbs! Does this sound right?

 

[PoolStored]

Are you finishing the test? Continue to add drops until the color NO LONGER CHANGES. Then subtract that last drop.
Test your fill water for CH. Is your autofill on a water softener?
I probably wouldn't raise your CH above 250 in phoenix with high CH fill.

 

[AZAA]

Are you finishing the test? Continue to add drops until the color NO LONGER CHANGES. Then subtract that last drop.
Test your fill water for CH. Is your autofill on a water softener?
I probably wouldn't raise your CH above 250 in phoenix with high CH fill.

Good call to try the fill water but no, it tested 170 and it is NOT softened water as our inside water is. I did the test as instructed, add drops until the sample turns from red to blue, 180 both days. I must assume that's correct. Calcium Chloride comes in 25 lb boxes from Amazon and they look huge. I'm supposed to add 35 lbs!? Just sounds like a lot.
Thank you for your response.

 

[Bperry]

I did the test as instructed, add drops until the sample turns from red to blue

that’s not the test instructions. You keep adding drops until the water stops turning MORE blue. If you stop early, the reading will be low, which is what yours sounds like for your area.

 

[JoyfulNoise]

I really wouldn’t add any calcium. Just ride your pH and TA higher. Since you’re running a liquid chlorine pool, just track the CSI so that it is roughly anywhere between -0.3 and +0.3 with zero being the sweet spot. Your pool will be fine otherwise. Summer evaporation and refill with municipal water should be fine for bumping up CH.

 

[AZAA]

that’s not the test instructions. You keep adding drops until the water stops turning MORE blue. If you stop early, the reading will be low, which is what yours sounds like for your area.

What! Stops turning MORE blue? Thats pretty subjective. Attached is a pic of the instructions from the K-2006:

 

[AZAA]

I really wouldn’t add any calcium. Just ride your pH and TA higher. Since you’re running a liquid chlorine pool, just track the CSI so that it is roughly anywhere between -0.3 and +0.3 with zero being the sweet spot. Your pool will be fine otherwise. Summer evaporation and refill with municipal water should be fine for bumping up CH.

Thanks. Even though the municipal water is 170 CH?

 

[JoyfulNoise]

Thanks. Even though the municipal water is 170 CH?

Water evaporates and leaves behind dissolved solids like calcium. Your CH will always increase over time. Calcium, like CYA, never goes down, unless fresh water exchanges for pool water.

 

[Bperry]

What! Stops turning MORE blue? Thats pretty subjective. Attached is a pic of the instructions from the K-2006:

It’s actually less subjective that way. If you add a drop, did it change the color or not? If it did change, add another drop and keep doing so until it stops changing. If you add a drop and it doesn’t change the color, you’re done and just remember to subtract the last drop from your count.

I also had trouble with this at first as well, but it makes more sense when you think about it. What looks blue to me might be sky blue or ocean blue to you. Which one is right? Is it the first sign of blue? There’s 1000 shades of blue, how do you know when to stop? That’s why all of the test end points (TA, FC, CH) are when the color stops changing. (Except for the salt test but that’s a different story).

The pH test is hard for people for the very reason you have to judge shades of color against a standard that sometimes doesn’t match the sample close enough.

 

[AZAA]

It’s actually less subjective that way. If you add a drop, did it change the color or not? If it did change, add another drop and keep doing so until it stops changing. If you add a drop and it doesn’t change the color, you’re done and just remember to subtract the last drop from your count.

I also had trouble with this at first as well, but it makes more sense when you think about it. What looks blue to me might be sky blue or ocean blue to you. Which one is right? Is it the first sign of blue? There’s 1000 shades of blue, how do you know when to stop? That’s why all of the test end points (TA, FC, CH) are when the color stops changing. (Except for the salt test but that’s a different story).

The pH test is hard for people for the very reason you have to judge shades of color against a standard that sometimes doesn’t match the sample close enough.

I'm still not following. The instructions say count drops until the sample turns from red to blue. Red to blue is a pretty easy concept. It doesn't say anything about continually adding drops until it turns some other shade of blue.
I appreciate you taking the time to help, but your instructions just don't make sense to me.

 

[PoolStored]

The purple color during the CH test is what is called fading endpoint. It is due to metals in your water. You need to go until you get blue.

But you might try using the fading endpoint procedure. Read Calcium Hardness

 

[Bperry]

I'm still not following. The instructions say count drops until the sample turns from red to blue. Red to blue is a pretty easy concept. It doesn't say anything about continually adding drops until it turns some other shade of blue.
I appreciate you taking the time to help, but your instructions just don't make sense to me

How are you defining blue? As you add more drops, you’ll find that the sample is slightly the hint of really light blue. Then as more drops are added, it gets more and more blue. The instructions are kinda unclear on this, I’d agree but it can make a huge difference in adding a big dose of calcium when you don’t need it.

The CH test (and the others as well) rely on the definition of blue (or red, clear etc) being consistent. So if you stop early, your test results will be lower than intended. Look through some threads on the subject and you’ll find this is not unique advice from just me.

 

[Bperry]

It’s actually less subjective that way. If you add a drop, did it change the color or not? If it did change, add another drop and keep doing so until it stops changing. If you add a drop and it doesn’t change the color, you’re done and just remember to subtract the last drop from your count.

I also had trouble with this at first as well, but it makes more sense when you think about it. What looks blue to me might be sky blue or ocean blue to you. Which one is right? Is it the first sign of blue? There’s 1000 shades of blue, how do you know when to stop? That’s why all of the test end points (TA, FC, CH) are when the color stops changing. (Except for the salt test but that’s a different story).

The pH test is hard for people for the very reason you have to judge shades of color against a standard that sometimes doesn’t match the sample close enough.

Let me try it this way. The color change from red to blue is not instantaneous. It slowly goes from red, to kinda clear then faint blue, then darker blue, then deeper blue. What criteria do you use to know when to stop?