Testing water with red/yellow drop tester.. question.

Hey all..

What does it mean if you test you pH with red drops and the resulting color is pretty close in color to the red drops themselves? Does that mean the pH is 0? It feels dumb asking that question, but previously my pH was around 7.2, so I have been adding a little bit of pH increase trying to bump it up but after testing today (after probably 2 inches of rain has fallen (NJ)) it looks as if it might be 0?

I have been shocking the crap out of my pool with about 72oz of granular chlorine every few days over the past month trying to clear it up after it turned swamp green after the hurricane. I'm sure that effects the PH reading so that's why I mention it.

My pool is a 24' round AG w/ sand filter and 1.5hp pump that I have been running 24/7 for a few weeks now.

Thanks in advance for your help.

Best case: 72 oz (4.5#) of "granular chlorine" is either 62% dichor or 65% cal hypo, and you've 4.5# of shock and 2.7# of chlorine equivalent. On a 12,000 gallon pool, that about 27ppm. That *may* be an effective shock level *if* (and only if) your stabilizer is below 100 ppm..

Worst case: you've got goop shock that's say, 20% chlorine equivalent AND you have 120 ppm stabilizer, so you've add only 9 ppm of chlorine to pool that needed 30 - 50 ppm repeatedly, to be effective!

What you need to know: shock doses that aren't effective, are essentially a complete waste.

And your question: a phenol red test result, where the sample remains a color similar to the original has a pH ~ 7.6.

But, do this:

#1 - Take your pool water to a couple of pool stores to be tested, and see if you can find out what your stabilizer level is. If two stores agree, there's a fair chance that that is a meaningful and somewhat accurate reading.

#2 - Meanwhile add shock OR plain 6% household bleach UNTIL the OTO (yellow side, clear drops) gives you a dark yellow / orangish reading . . . and then keep dosing to MAINTAIN that level of chlorine . . . no matter how much you have to add. With bleach, 5 gallons of 6% bleach is a reasonable starting dose for your pool.

#3 - While at Walmart getting bleach, ALSO buy 1 gallon of plain *distilled* (not: bottled, crystal, spring, natural, etc) water. While your chlorine is high, mix your pool water sample 50:50 with distilled water and then test the mix. This will still give an accurate pH results, and will keep the chlorine from messing up your test. (Collect 1/2 cup of pool water; pour it into a large glass container. Add 1/2 cup of DISTILLED water & mix. Fill your test kit with the mix, and test pH. Do NOT test chlorine this way!!)

#4 - Read the "Best Guess" page linked below.

#5 - If you really want to get control of your pool, order a K2006 test kit (Amazon links below), so you can get accurate test results for chlorine and stabilizer -- 'guess' strips are NOT accurate enough, especially for stabilizer results.

#6 - Report back once you have some sort of information regarding your stabilizer level.

Good luck!

Hey PoolDoc,

The granular chlorine is 47.6% Calcium Hypochlorite and 52.4% "other ingredients".

Thankfully I can see the bottom of my pool finally, though the water is still cloudy. I have tried to keep the chlorine tests in the dark yellow range but didn't realize the stuff I was using was not sufficient. Of course I was following the label in regards to the "shock level" and actually thought I was putting in a little more than necessary. Guess not!

Ive also been putting in "Jumbo slow-poke" tablets thinking that would help keep the levels up.. Those are listed as 99.5% Trichloro-a-Triazinetrione and .5% other. Basically keeping 2 or so in a floater and dropping one in the skimmer basket.

If my pool is no longer green and semi clear.. should I still follow your recommendations to finish clearing before closing?

I guess that's good news about the pH. According to my tester.. the color for 7.6 is more of a purplish/lavender color.. so the color the water was showing wasn't like any of the colors listed on the tester.


Thanks again for the info.

Hi Mastamoon;

I didn't know that what you were using was bad -- I just didn't know if it was good. So much goop is blended in these days, in order to lower the manufacturer's costs AND raise the price, it's hard for us to know just what you are putting into your pool, or what effect it will have.

If the pool is clearing that's very good, and indicates that you do not have a super-high stabilizer level, or a chlorine resistant strain of algae. But, the advice I gave you is still correct, especially the bit about testing pH with a 50:50 pool water / distilled water mix.

And, do keep your chlorine in the orangish yellow range till the algae is ALL gone.

Best wishes,

If the water is slightly cloudy is it always an algae problem and/or a chlorine fix?