Longtime reader finally joined

Well, since you asked....

Every year I have just been adding chlorine and balancing PH. All was well! Until it wasn't....

This year, my vinyl liner has some brownish-green staining on it that look like algae but will not respond to brushing. I decided to super-shock the pool but I was guessing at many variables (thus the test kit).
The stain has been there for two weeks of very high chlorine levels. It is all over the bottom and on the steps, plus a small amount on the walls. I have brushed (and brushed and brushed) and kept the chlorine super high and ran my Dolphin robot almost constantly. I always keep my pump running. My pool is inground with a vinyl liner. Capacity is about 11,000 gallons. Water temperature has been 80-86 degrees last two weeks. The pool is six years old.
When I opened the pool, there were several leaves that got in there under the automatic cover over the Winter. I think the stains could be tannins from the leaves if they aren't algae.

The brown stains do respond to chlorine put directly on them for a few minutes, so I think they are organic. I have not tried ascorbic acid. The water has been crystal clear since a few days after I opened the pool (about six weeks ago). It is always nasty when I open it, and I thought the stains would just go away in a few weeks.

I tested my water last night with the TF-100:
CYA is 70+ (possibly 100, but I can still see a black dot until 70...that test is pretty subjective)
PH is 7.2
TA is a mystery. It never turned red after 60 drops, but it did turn yellow after just a few drops (I wasn't counting as I was waiting for red), so it may be 30-60 or it may be over 600
FC is 46 (that is not a typo, and that was without adding chlorine for two days)
CC is 2
TC is 48 (after not adding chlorine for two days)
I didn't test for calcium hardness since I have a vinyl liner pool.

Yes, I have used a lot of the chlorine pucks and pool shock granules over the years. I will refrain from using anything but liquid from now on.

I am stumped!

Please excuse my ignorance. I haven't really studied up on all of this because all has been well. I have read many posts here over the years and appreciate the expertise!

Jeff

PoolStored said:

How much, when and of exactly what product did you add to the pool?

Can you explain exactly how you test FC and CC? Sample size? Number of drops?

Click to expand...

I used several gallons of bleach and liquid pool shock. I also used a few pounds of granular pool shock and a few of the dreaded pucks (both from Doheny's, and I'm not sure exactly what they were) that I had left over before switching to liquid.
I was putting two or more gallons a day in for about two weeks just to see if the staining would go away since it went away where the granular shock fell on the liner.

I tested FC and CC using the method described in the instructions. I read them very carefully. It took 92 drops. I almost gave up.
If I use the basic PH and Chlorine water test with the red and yellow chart and the 5 drops each, the chlorine side is ORANGE with some sort of precipitate floating in it. I have definitely never seen that before. It is definitely not yellow at all. It is still like that today, and no chlorine has been added since Saturday, and it stormed yesterday. There were leaves and twigs and an inch of new water since the chlorine was added.
Keep in mind, I was trying to either kill algae or bleach a stain, so I wasn't concerned about too much chlorine. I was trying to get my chlorine up super high and all my tests (strips and the basic red/yellow CL/PH/5 drops tests) only go up to 5ppm or 10ppm.

The stains are still there!

In the beginning (5 years ago) I used the ridiculous FROG system my builder installed with the mineral pack and chlorine packs, but I didn't use more than two mineral packs and maybe a dozen chlorine packs. I thought they were expensive and ineffective and found this forum looking to reinforce my presumption.

I went outside and did the simple test again just now (see above). My pH has raised a little and the Cl is less orange, but still far from yellow.

I tried to take pics of the staining, but it’s difficult to see under most lighting. It shows up best when it’s overcast and it’s almost invisible in bright sunlight or at night. I’ll go run the FC again now.

dBsooner said:

Is that second pic a zoom in of the first? It looks awfully green.

Click to expand...

The lights change colors and it was on a green hue. They are different pics.

PoolStored said:

Post some pics of the staining, likely from the metals in the mineral packs, could be organic if the granular took it away.

Try the FC test again. Use 5ml sample. Each drop is 1 FC. Same with the CC.

Let's get the FC under control first. Let it drift down. Don't add anything to the pool until your FC is <10, and you post a full set of results.

Click to expand...

I went ahead and did the 10ml sample. it took 89 drops, so
FC 44.5
CC 0