Brown stain under autofiller jet?

[bevodive]

Hello everyone,

We had out pool finished since March, 2024 (filled at the end of March), and I've been following TFP since we opened. Everything is going great so far. However, the other day I noticed a very light discoloring (brownish) under the autofiller jet in the deep end. It almost looks like something trickled out of the jet, as the stain is long and skinny. It's hard to see in the attached picture, but it's faintly visible in person. I've tried brushing the past couple of days, but it doesn't seem to be fading. Any idea what this could be? Any idea how to remove it? I swear it wasn't there until a couple of days ago. My numbers are as follows (as measured every other day with Taylor K-2006):

PH - 7.6-8.0
TA - 70
CYI - 45
TC - 4.0
CH - about 350

 

[reggiehammond]

On city water? Well water?

CYA is logarithmic - there's no 45. You should use 50.
50 CYA is minimum 4 FC, range 6-8 for liquid FC pools.

You may have some algae given the low FC - might consider a Overnight Chlorine Loss Test to make sure the stain is not organic.

 

[bevodive]

Thank you. It's city water. I'll try an overnight loss test. Any reason think maybe an iron stain from water coming from autofiller?

 

[bevodive]

On city water? Well water?

CYA is logarithmic - there's no 45. You should use 50.
50 CYA is minimum 4 FC, range 6-8 for liquid FC pools.

You may have some algae given the low FC - might consider a Overnight Chlorine Loss Test to make sure the stain is not organic.

So I lost about 1.4 ppm of chlorine over night. Can I assume that's algae? I'm also going to rub some vitamin C on it and see if that helps.

 

[reggiehammond]

Would be great to post a full set of test results. 1.4ppm (use 10mL sample and one scoop of powder in future for 0.5ppm accuracy) is likely more than you'd expect with no UV exposure. SLAM Process might be something you need to do to make sure there's no organics.

Could definitely be dirt or stain from auto filler mechanism; hard to say.