Eating chlorine

[Punchyp]

I think i had some kind of black algea on bottom of pool. I thought it was just dirt and tree debris at first. I vac'd and the next morning it wad back, but not as much. I started the slam process on a tuesday, its saturday now and it will not stop eating chlorine. Trying to keep it the target of 20 has been difficult. Its losing 5 overnight and yesterday it went from 28 at 1030am to 13 at 730p. i bet used 8 gallons this week. Water is clear, CYA 40 TA90 PH? it was 7.4 when started slam.
Cartridge filter, changed daily after vac. WHAT THE HECK?

 

[Texas Splash]

Sounds like you may have algae in more places that just what you see on the bottom. Do you have a ladder, hollow steps, or a pool light with a hollow niche behind it? Main drain perhaps? Any of those could result in hiding places for algae as well.

 

[mknauss]

Are you still fighting iron as is being discussed in your other thread? Many of the sequestrants for metals can effect FC levels.

But if you are losing FC due to organics as shown by your OCLT numbers, stay at SLAM level FC.

 

[Punchyp]

Sounds like you may have algae in more places that just what you see on the bottom. Do you have a ladder, hollow steps, or a pool light with a hollow niche behind it? Main drain perhaps? Any of those could result in hiding places for algae as well.

I do have a wall ladder and light in a hollow niche.
Heres a picture of it this morning(5/8/20) as for the iron, it is still staining but not as bad as last year and i have not added any sequestering agent since early april. Anytime the chlorine or ph goes up, the stains come back.

 

[Texas Splash]

Anytime the chlorine or ph goes up, the stains come back.

Sure. Makes sense. Well, perhaps that ladder or niche will unlock the secrets to your trouble. Let us know how it goes.

 

[Punchyp]

So my fc has still not stabilized and i fear i have a leak somewhere. Lost 3/4 inch in 24 hours. Lost 7 pts of fc during daylight and 2.5 overnight. Will a hole in liner cause fc to be consumed like that? I see a spot on bottom that could be the culprit

 

[IceShadow]

No, chlorine is consumed by organics and by sunlight. If you add water to your pool all your chems will be lowered a bit (except whatever TA and CH your water might have), but 3/4” is not going to make a difference. Did you take out the ladder and inspect it, check behind the light for algae, etc.?

 

[Punchyp]

I havent taken light out yet, I'll do that later today. Im not sure how to get the ladder out of the wall. Could my leak be in the light socket also? Its 22 years old and never been touched. On the right side of this pic is the rusty looking spot on the bottom. The square tile print are about 1/2 squares.