Hard time measuring calcium hardness

[Pierrot]

Hi,

I'm using the Taylor test kit. I don't have any issue with measuring the various chemicals... except the calcium hardness. When adding the reagent, I don't have a clear cut between red and blue. The water slooooowly transitions from red, to purple, to light blue, to blue. So my calcium hardness is somewhere between 400ppm and 650ppm.

I read it could be caused by copper. I believe I have some (I'm not sure where it comes from, I only use liquid chlorine and muriatic acid. Probably a left over from the previous owner? Anyway..). I also read that adding some drops of the re-agent first would help. It didn't for me.

Here is what I did:

• used 10ml water sample, then added:
• 8 drops of the reagent (R-0012)
• 10 drops of R-0010
• 5 drops of R-0011
• then added R-0012 drops again.

It started turning purple after 16 drops of R-0012 (including the ones added at step 1), and the last drop after which the color didn't change anymore was the 25th one.

When I get the water tested at Leslie's, they tell me my calcium hardness is 350ppm (I know the TFP community doesn't recommend pool store testing, but for other chemicals their measures are consistant with what I get, so I think they do it right).

 

[PoolStored]

The 25th drop is your answer. After it doesn't change again.

Get a speed stir. It is a game changer. You will have ZERO question about your CH levels.

Smart Stir Magnetic Stirring Device

tftestkits.net

 

[Pierrot]

Would the stir make the color change faster (ie no more purple, just straight from red to blue), or will it just help me better focus and see if the color still changes after each drop?

 

[PoolStored]

See if the color still changes...and hit has a light, which really helps seeing the color change or no change.

 

[reggiehammond]

CH testing in my pool water is also tricky - there's not a lot of color initially, so judging when it changes is also hard.
Wish I had some magic trick - I've tried a few things. The best I've come up with is more light, and a white background immediately behind speed stir vial.

 

[Gotta Pool]

CH can be a bit tricky due to a phenomenon called "fading endpoint." As always, Taylor has your back and very complete manufacturer instructions including gotchas like this. Follow this link...

 

[reggiehammond]

If OPs test is anything like mine, the issue is that I only have 20% of the color shown in the Taylor examples. It's very light.

 

[mknauss]

Cut your pool water 1:1 with distilled water. Do the test with the mixed water. Double your results. It really helps with the 'fading endpoint'. Issue is iron in our Colorado River water.

 

[Pierrot]

Many ideas to test. Thank you all!