Chlorine spike (comparator vs drop test)

[mjrogers]

Moved into a new house with 25,000 gal (best estimate) chlorine in-ground pool (built in the 70's); Finally got the pool cleaned and just about everything where I want it. However, free chlorine is all over the place despite following the Pool Math recommendations. pH keeps rising every 2 days. Water looks amazing (sparkling and clear to the bottom). I bought the digital pH meter from TFT, but it didn't work, so for now I have to guess using the comparator block. Maybe I'm just really bad at matching the comparator block colors.

May 5 & 6
FC 3.0 (comparator)
pH 7.8
+ 18 oz 31.45% (20o Be) Muriatic Acid
+ 64 oz liquid chlorine 10%
May 7
FC 5.0 (comparator)
ph 7.5
May 9
FC 3.0 (comparator)
pH 7.8
+ 64oz liquid chlorine 10%
May 10
FC 12.0 (TF drop test)
pH 7.8 (comparator)
CC .5
TA 60 (should I target 70?)
CH 375
CYA 40 (should I target 50?)

 

[PoolStored]

Let's start here.

1. For now, until you learn your pool, CYA of 40 is just fine. Don't change it.
2. Chlorine is King. Use the FAS-DPD (R-0870 powder and R-0871 reagent) to test FC and CC. Use a 10mL sample, each drop is .5 FC and .5 CC. Don't use the comparator for FC testing.
3. When you chlorinate, your target FC is based on your CYA level. Use this tool (link), with your 40 CYA to determine your FC target. Link-->FC/CYA Levels
4. Your goal, for now, is to be at the top of the FC range, WHEN YOU TEST. If you have to dose above range, so that when you test you are in range, do that.
5. Your Ph and TA are just fine. Don't worry about TA unless it is below 50. Just maintain a pH of 7.6-8.0 and you will be just fine. Don't lower pH until you see purple hues, and then only lower to 7.8. You will be great.

Do this for now, and maintain your FC for a bit before you raise CYA.

 

[Dirk]

@PoolStored has you covered. Follow each of his instructions to the letter.

so for now I have to guess using the comparator block. Maybe I'm just really bad at matching the comparator block colors.

Regarding pH testing, this is what works for me. The Taylor pH test (comparator) is one of the easiest tests to perform. You can trust it 100%, and its results are not a guess. If you're having trouble comparing colors, try these tips:
- Find a color neutral source of light (I use white, under-counter LED lights), and a stark white card (like a 3x5 recipe card). Hold the comparator under the light(s) in one hand, and the white card in the other hand. Tilt the card such that the LED light bounces off of it and shines through the back of the comparator. Adjust the position of the comparator and the card, relative to each other and the light source, until the colors "come into focus." You'll know it when you see it.
- That should help a lot. If the colors still don't seem to match, try using four drops of R-0014 instead of five. This will lighten the colors a bit. I find that this "adjusted" color matches my comparator much better.
- If you're still struggling with finding the exact match, try this. After filling the side with pool water and adding four drops, mix gently. Focus on only one comparator color block, start in the middle. Don't look at the other colors for now, just compare the one color to the pool water. Ask yourself, is the pool water more orange than the color block, or more magenta. If more orange, focus on the next block down and ask the same question. If more magenta, focus on the next block above. Repeat this process until you cannot see that the pool water is more orange or more magenta than the block you're focused on. That block's pH number is the result.

Sometimes this orange/magenta comparison leaves you between two blocks. For example, more magenta than 7.4 but more orange that 7.6. That's fine, your pH is 7.5!

With a little practice, you'l be able to quickly dial in your pH number. Faster and more reliably than a pH meter. No batteries. No calibration. No fumbling with an electronic gizmo.

Now if none of that works, it's possible you've got a touch of color blindness. Some people cannot use a comparator because all the colors look the same. If that's the case, you've got two choices: figure out the pH meter, or have someone else in the household help you with the comparator.