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Why Won't The Ch Go Up?


RonB01
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I just changed the water in my tub. The initial test was TA 30, CH 30. I brought up the TA with 1 tablespoon baking soda. Also shocked with dichlor to 10 ppm, added a pound boric acid for borates, and ran the jets to bring pH up.

Later that day, the test was TA 40, CH 30. I added another tablespoon baking soda.

The next test, same day, was TA 50, CH 30. So, I added a tablespoon of calcium chloride to start CH up.

The second day, I had a CH of 75. So, I added another tablespoon of calcium chloride to bring CH farther up.

Three days later, having added another tablespoon each day, CH is still reading 75. In other words, I have added 4 TBS (2 oz) calcium chloride with no change in the reading.

I am using the Taylor 2006 test kit, which is only a month old.

Any ideas what is going on here?

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You aren't using any sort of phosphate-based pH buffer product or any metal sequestrant, are you? What is the volume of your spa? In 350 gallons, one tablespoon of baking soda raises the TA by about 8 ppm so is consistent with what you are seeing. One tablespoon of calcium chloride anhydrous should raise the CH by about 12 ppm (calcium chloride dihydrate would raise it about 6 ppm). So your first day of calcium chloride addition increased the CH by more than expected while subsequent additions aren't changing the reading. Make sure that the drops are coming out normal and hanging -- wipe the dropper tip in case their is static electricity.

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You aren't using any sort of phosphate-based pH buffer product or any metal sequestrant, are you? What is the volume of your spa?

No, the only thing I am using for "buffer" is the boric acid. These are new filters that I just got to have a set to swap, so it isn't un-rinsed tsp either.

The spa is 420 gallons.

I'll pay closer attention to the size of drops, but didn't notice anything different.

Could temperature have anything to do with it? The test kit is kept in a cool room, about 50F.

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Could temperature have anything to do with it? The test kit is kept in a cool room, about 50F.

No, that shouldn't matter for the CH test though getting the sample to room temperature might be reasonable to do.

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  • 2 weeks later...

Could temperature have anything to do with it? The test kit is kept in a cool room, about 50F.

No, that shouldn't matter for the CH test though getting the sample to room temperature might be reasonable to do.

I am also seeing something similar. I refilled the tub, shocked with dichlor. I've started to adjust the PH and TA, but also wanted to up the calcium hardness to 150ppm. I started at about 0-10ppm. So we purchased some "Calcium Up" which says it should raise the calcium hardness by 30ppm per 3oz capful in a 500 gallon tub. My tub is 475 gallons. I put in 3 capfuls and let the tub run for a few hours to dissolve. I then tested again and it was right at 10ppm. I put in another 3 capfuls and tested again after 12 hours. I'm at 30ppm now. I'm wondering if the "Calcium Up" is just going to raise this level way slower than I thought? The product is "Calcium Up" by Proteam. It is a 1lb bottle of crystals, but doesn't show any % of anything. Should I just keep adding and retesting? I'm testing with a Taylor kit.

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For the CH test, you are waiting for the sample to go all the way from red to blue, correct? You aren't stopping at purple, right? See this link for an example of a color change. If you are getting purple or a color that doesn't stay blue, then this is a fading endpoint. You can prevent that by adding some titrant drops (say two, in your case) before adding the calcium buffer and indicator dye. Then be sure to count those initial drops in your total titrant count.

You can also see a complete set of videos by clicking on this link and then clicking the "Pool / Spa" category on the left and then scrolling down to select the appropriate video to watch.

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For the CH test, you are waiting for the sample to go all the way from red to blue, correct? You aren't stopping at purple, right? See this link for an example of a color change. If you are getting purple or a color that doesn't stay blue, then this is a fading endpoint. You can prevent that by adding some titrant drops (say two, in your case) before adding the calcium buffer and indicator dye. Then be sure to count those initial drops in your total titrant count.

You can also see a complete set of videos by clicking on this link and then clicking the "Pool / Spa" category on the left and then scrolling down to select the appropriate video to watch.

Ah once again you get a big win. :) I didn't have a chance to check it again tonight, but I'll try starting with a few drops of titrant in the beginning and going from there. I was taking the change in color from red to blue as the time when I could no longer see any red. I suppose the video and webpage explain it a little bit better. Although the changed color did look a bit purple, or a blueish purple, the red doesn't exactly appear bright red either, more of a pink. I'll do more analysis tomorrow and report my findings. Thanks again.

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For the CH test, you are waiting for the sample to go all the way from red to blue, correct? You aren't stopping at purple, right? See this link for an example of a color change. If you are getting purple or a color that doesn't stay blue, then this is a fading endpoint. You can prevent that by adding some titrant drops (say two, in your case) before adding the calcium buffer and indicator dye. Then be sure to count those initial drops in your total titrant count.

You can also see a complete set of videos by clicking on this link and then clicking the "Pool / Spa" category on the left and then scrolling down to select the appropriate video to watch.

Ah once again you get a big win. :) I didn't have a chance to check it again tonight, but I'll try starting with a few drops of titrant in the beginning and going from there. I was taking the change in color from red to blue as the time when I could no longer see any red. I suppose the video and webpage explain it a little bit better. Although the changed color did look a bit purple, or a blueish purple, the red doesn't exactly appear bright red either, more of a pink. I'll do more analysis tomorrow and report my findings. Thanks again.

I tested today again and came out around 50ppm, adding 2 drops of titrant before everything else and 3 after the calcium buffer and indicator dye.

The one funny thing I noticed is the calcium up product says to use 1 level capful which equals 3oz. I've put in about 6 level capfuls total and I've only used about 1/4 - 1/5 of the bottle. The bottle shows that it is the 1lb bottle. If a level capful is 3oz and a pound is 16oz, the bottle should only be about 5-6 capfuls and it is WAY more than that. With that being said, I believe the level capfuls I've been putting in are around .75oz and thus why 6 capfuls only raise my calcium hardness about 50ppm. Does this seem right? The guy at the tub store told my girlfriend that she shouldn't need to add very much to get the hardness up, but at this rate, we would be adding almost the entire bottle to get to around 150ppm.

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it does take a lot to raise the CH level. Out here we are at zero CH out of the city tap and in my 500 gallon spa it takes a pound plus to get my CH up, good thing is that it stays in the water unless you splash out a lot!

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it does take a lot to raise the CH level. Out here we are at zero CH out of the city tap and in my 500 gallon spa it takes a pound plus to get my CH up, good thing is that it stays in the water unless you splash out a lot!

Ok, I'm glad someone is seeing the same numbers that I am!! At the rate I'm seeing, the 16oz would raise the hardness about 160ppm, which is what I need. I just can't figure out why the bottle is saying the capful should raise it 30ppm and that the capful is 3oz. It is a small cap and they are saying that it holds about 1/5th of the bottle of stuff, that can't be even close.

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Sometimes product changes are made, such as the size of caps, without changing the instructions. Or the instructions could have always been wrong.

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