Questions about FC, CYA, and PH. New pool owner.

[Wieldy]

Hello,

28k-30k gallon vinyl pool
My test results from this morning are at the bottom.

I added 3 pounds of cal-hypo last night and tested this morning. I didn't see any change in chlorine levels, and my pH went DOWN which I thought was odd. Calcium went up 10ppm from last test about a week ago but I assume that's just because of the cal-hypo.

I'm going to add 4lbs of stabilizer to raise it to 45ish and raise pH to 7.6 today.

Question: Why would there be no change at all in FC numbers after add 3lbs of cal-hypo?

Test Results
FC: 0.5 (estimate)
pH: 7.2
TA: 70
CH: 100
CYA: 25-30 (dot is JUST barely visible at the 30 mark)

p.s. There was a brownish stain at the deep end that wouldn't brush off. When I added the cal-hypo to the deep end that stain just disappeared. Thought that was weird.

 

[PoolStored]

Welcome to TFP!!!

I added 3 pounds of cal-hypo last night and tested this morning. I didn't see any change in chlorine levels, and my pH went DOWN which I thought was odd. Calcium went up 10ppm from last test about a week ago but I assume that's just because of the cal-hypo.

The lack of change in chlorine levels likely means you have algae.

I'm going to add 4lbs of stabilizer to raise it to 45ish and raise pH to 7.6 today.

Let's hold off adding stabilizer until we figure out the algae situation. Will make it easier to fix.

Question: Why would there be no change at all in FC numbers after add 3lbs of cal-hypo?

Algae. Even if you can't see it.

Test Results
FC: 0.5 (estimate)
pH: 7.2
TA: 70
CH: 100
CYA: 25-30 (dot is JUST barely visible at the 30 mark)

With FC of .5 and CYA of 30 (you always measure at the lines, not between), you likely have algae.
We always follow the FC/CYA relationship recommendations. Your FC is low enough that you cannot kill bacteria and algae. Link-->FC/CYA Levels
How do we figure out if you have algae? You need to run an Overnight Chlorine Loss Test Link-->Overnight Chlorine Loss Test
To do that you will need to upgrade your K2005 with either a FAS/DPD addition or get one of these kits. Link-->Test Kits Compared
If you have algae, you will need to SLAM Link-->SLAM Process

 

[IceShadow]

If the stain disappeared with the addition of chlorine then it was likely organic in nature. My steps look awful when I open in spring from leaves that sneak under the cover over the winter, but the stains go away with a couple of days of chlorinating.

 

[woodyp]

The over night chlorine loss test (OCLT) answers a lot of questions when you get your kit.

 

[Methuselah]

Did you get your chlorine level up?
I'd suggest unscented bleach or pool chlorinator (the link to poolmath below is helpful)