Opened pool 3 days ago. Everything great until today - black marks on bottom

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D

DivingIn

0
Jul 31, 2014
41
Toledo, Ohio
Pool Size
17000
Surface
Vinyl
Chlorine
Liquid Chlorine
This is my 16th year opening my pool. Three days ago I did what I do every year. Began filtering 24/7. Vacuumed sides and bottom. Changed DE 3 times. Water got clearer every day. Today it was very clear. There was some dark residue on the bottom of the deep end, so I vacuumed it away this afternoon. But there are some dark spots (streaks) that won't vacuum up or brush away. These spots were not there this morning. I've never seen anything like it.

I never have algae problems. I've kept the Cl >2 since the start (3 days ago). I put a lot in to keep it there, which I do every year. Today the solar cover was on all day. I took it off, vacuumed the deep end like I said, and the black areas are there.

The liner is 10 years old.

Any thoughts? What could this be? I can't include a photo right now because it's too dark.
 
DivingIn said:
This is my 16th year opening my pool. Three days ago I did what I do every year. Began filtering 24/7. Vacuumed sides and bottom. Changed DE 3 times. Water got clearer every day. Today it was very clear. There was some dark residue on the bottom of the deep end, so I vacuumed it away this afternoon. But there are some dark spots (streaks) that won't vacuum up or brush away. These spots were not there this morning. I've never seen anything like it.

I never have algae problems. I've kept the Cl >2 since the start (3 days ago). I put a lot in to keep it there, which I do every year. Today the solar cover was on all day. I took it off, vacuumed the deep end like I said, and the black areas are there.

The liner is 10 years old.

Any thoughts? What could this be? I can't include a photo right now because it's too dark.
Click to expand...
Chlorine that low sounds like algae.
 
Without pictures, all we can do is guess.

Maybe black algae, copper, bacteria under the liner etc.

Copper is the only thing that would appear quickly.

Are you saying that the stains were definitely not present this morning and they suddenly appeared?

What was added?
 
Well, they weren't present yesterday evening when I put the solar cover on. The bottom was clear. Last night I added a little washing soda to raise the pH a little. I had already added a box of Borax on Sunday. This morning I added 1 lb of calcium hypochlorite to keep the Cl above 3. This after I added another lb. of it. I did a fresh change of DE in early evening. Then I took the solar cover off and vacuumed the debris off the bottom, and that's when I discovered the spots.

I will post a photo in the morning.
 
Here's what the black areas look like this morning. The areas have expanded overnight.
Current levels:
TC 5
FC 5
TA 70
pH 7.9
Temp 73
CH 50
CYA 0

The areas do not brush or vacuum off. They are in the deep end (9 ft.)

Black areas 01.jpg

Black areas 02.jpg

Black areas 03.jpg
 
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DivingIn said:
Yes, currently no stabilizer. The pool has been covered during the day. I will add some, but I don't think that has anything to do with the black areas.
Click to expand...
Maybe not directly but it helps point to how much active chlorine is present. Are those test results from one of the TFP kits? If so, the stabilizer may just be lower than 30ppm. Is the chlorine measurement from FAS-DPD or the yellow OTO test?
 
Bperry said:
Maybe not directly but it helps point to how much active chlorine is present. Are those test results from one of the TFP kits? If so, the stabilizer may just be lower than 30ppm. Is the chlorine measurement from FAS-DPD or the yellow OTO test?
Click to expand...
All test results except CYA are from Taylor kits. Chlorine is from FAS-DPD
 
DivingIn said:
Yes, currently no stabilizer. The pool has been covered during the day. I will add some, but I don't think that has anything to do with the black areas.
Click to expand...
Higher levels of fc can sometimes make metal stains show themselves (5ppm w/ no stabilizer is a little high)
Have you been doing any fertilizing in the yard recently where something could have blown in?
 
Looks like you had a similar issue before?

Maybe copper or maybe something under the liner.

Try putting some vitamin C on a spot.

Algae after 3 weeks of non-use?

I was away from my pool for three weeks. I use the trouble-free method and never have any problems. When I took the solar cover off upon returning home, the water looked fine, but there are several large light-gray or light-green blotches on the bottom of the pool, both in the shallow and deep...
www.troublefreepool.com www.troublefreepool.com

img_9017-copy-2-jpg.32408
 
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JamesW said:
Looks like you had a similar issue before?

Maybe copper or maybe something under the liner.

Try putting some vitamin C on a spot.

Algae after 3 weeks of non-use?

I was away from my pool for three weeks. I use the trouble-free method and never have any problems. When I took the solar cover off upon returning home, the water looked fine, but there are several large light-gray or light-green blotches on the bottom of the pool, both in the shallow and deep...
www.troublefreepool.com www.troublefreepool.com

img_9017-copy-2-jpg.32408
Click to expand...
No copper in water. I'll try the Vitamin C when I go into the water
 
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