pH color deciphering

I thought that what I was experiencing with my pH tests had to do with older reagents - but I replaced them Friday and I have the same issue:

When I test my pH with my trusty K2006 kit, the color endpoint is not a blue-red cast - its more of a yellow-red - BUT it is not in the acid range as far as I can tell. I have been guesstimating my water to be pretty solid at around 7.5 because the intensity of the color fits between 7.4 and 7.6. I get the same color point with the old and new reagents and with 2 separate comparator blocks I have.

When I test with my daily rainbow, I am getting a definite blue-red color set and it appears to be in the basic range - as if I need acid added.

When I tested my rainwater - which has been a lot lately - it is below 6.8 in all three tests. My alkalinity is steady between 70-80 since I opened in May.

I don't know what sets of numbers to go with. :confused:

I have a 24K IG vinyl 18x42 with a Hayward 1hp SuperPump and Hayward EC-65 DE filter.

Color intensity isn't what you are looking at, it is the hue. Yellow red would indicate acidic water. Deep scarlet red indicates basic water. Try holding the test vial in front of a white background in natural light.

Ok, so the "big" kit is telling me I have acidic water and the little one is telling me its basic - based purely on color. And I do hold it up against white whenever I test it. Do I go with the big kit results? Should I add borax or baking soda? Thanks!

What is your chlorine level? Sounds like you are getting chlorine interferance in your rainbow kit. The phenol red in the Taylor kit has a chlorine neutralizer included in the reagent and will work with chlorine levels up to about 15 ppm. the rainbow phenol red does not. What is happening is the phenol red in the rainbow kit is being converted to chlorophenol red which tests the pH range of 4.6 to 6.8 with the same color changes as phenol red has from 6.8 to 8.2 so the purple color you are seeing means the pH is above 6.8! Yellow-orange color should put your pH in the neighborhood of 7.2-7.4. Orange is about 7.4-7.5. Hope this helps.

Evan, thanks for the info! Would a couple of drops of thiosufate correct the Rainbow kit and vice versa, could the Rainbow kit be used to test REALLY LOW pH if a few drops of bleach were added? (every year we lose a few copper heat exchangers due to low pH/ alk and I'd like to know how bad the water is so I can properly adjust it - as for why this happens, the owners use only tri-chlor pucks and [the antithesis of CarlD's advice] 'spend 2 - 5 minutes a year to buy a new heat exchanger' - no joke, there are some we replace every year :eek:and tell them how to avoid it.)

Quote:

---

Originally Posted by waste

Evan, thanks for the info! Would a couple of drops of thiosufate correct the Rainbow kit and vice versa, could the Rainbow kit be used to test REALLY LOW pH if a few drops of bleach were added? (every year we lose a few copper heat exchangers due to low pH/ alk and I'd like to know how bad the water is so I can properly adjust it - as for why this happens, the owners use only tri-chlor pucks and [the antithesis of CarlD's advice] 'spend 2 - 5 minutes a year to buy a new heat exchanger' - no joke, there are some we replace every year :eek:and tell them how to avoid it.)

---

a drop or 2 of chlorine neutralizer should work to remove some interferance...don't really know abut the other way round. You would really need a comparator for the chlorophenol red to get an accurate reading...some soil testing kits have indicators in lower pH ranges...might be an option to explore.
Some people just don't want to deal with their pools. If they won't take the time to take care of their water I say make all the money you can off of them with the new heat exchangers every year! :rolleyes:

[What is your chlorine level? Sounds like you are getting chlorine interferance in your rainbow kit. The phenol red in the Taylor kit has a chlorine neutralizer included in the reagent and will work with chlorine levels up to about 15 ppm. the rainbow phenol red does not. What is happening is the phenol red in the rainbow kit is being converted to chlorophenol red which tests the pH range of 4.6 to 6.8 with the same color changes as phenol red has from 6.8 to 8.2 so the purple color you are seeing means the pH is above 6.8! Yellow-orange color should put your pH in the neighborhood of 7.2-7.4. Orange is about 7.4-7.5. Hope this helps.]

Here are 2 sets of numbers from yesterday:

3 pm:
FC=2.5
CC=0
TC=2.5
pH=7.5 (assumption)
Alk=75
CYA= Assumed less than 30

At 8 pm after 100 degree heat, 3 little kids and addition of 1.46 galls and 3 qts bleach, 1 lb borax:
FC=8
CC=.5
TC=8.5
pH=7.5 (assumption)
Alk=75

I haven't tested it yet today (pool's at my mom's house)