Iron and Algae

[EdKuhn]

Hello everyone, been awhile since I've posted. Every spring I have brown staining on my white fiberglass steps that I remove with vitamin C tablets. I also had staining on my vinyl liner and this year I tried the vitamin C on a small area, and it removed the stain. So I rigged a sock on an old vacuum head and filled it with vitamin C tablets and over a period of a few days got rid of the staining throughout the pool. Looks great. Fast forward to early this week and I had algae pop up, evidenced by lower CL and daily buildup of dead algae on the bottom of the pool. Water was perfectly clear however.

I began a SLAM, target CL was 28 based on my CYA (see pre-slam data below). I've kept up the SLAM for four days now and the water is absolutely beautiful, no dead algae, no CC, but I'm still losing CL on the overnight test (last night went from 29 to 25). I'm stumped and running out of chlorine. My question is could the dissolved iron and/or the dissolved vitamin C be consuming my CL? I've seen old posts about ascorbic acid treatments and how ascorbic will consume CL, and I'm wondering if that could be the issue. I used about three bottles of 1,000 mg vitamin c during the whole stain removal, probably around 750 tablets total. That sounds crazy now that I've typed it out!

Pre-SLAM data:
CL 6.5
CC 0
pH 7.2
Alk 70
CYA 70
CH 50

Thanks for any help!

 

[Texas Splash]

My question is could the dissolved iron and/or the dissolved vitamin C be consuming my CL?

In your case I don't think that's the issue. You've been maintaining a high FC for too long now anyways. Do you have any hiding spots not yet exposed like a ladder, hollow steps, or behind a light fixture in a niche? Maybe a drain cover (underneath)?

 

[EdKuhn]

In your case I don't think that's the issue. You've been maintaining a high FC for too long now anyways. Do you have any hiding spots not yet exposed like a ladder, hollow steps, or behind a light fixture in a niche? Maybe a drain cover (underneath)?

I'm brushing everywhere, took the light out of the niche, brushed the ladder, steps, skimmer. Maybe I'll take the ladder out and see if there's anything inside. Its usually rusty though. Not sure if I can do anything about the drain cover. The iron stain is coming back on the steps. Likely over the whole pool but just not as noticeable as the white steps are. I have an iron problem for sure but local stores are out of the test reagent to see what kind of level I have.

 

[Texas Splash]

The hollow areas in ladders can be problematic. Over time, drains can accumulate muck underneath the cover that becomes a breeding ground for algae. Being sure of each of those areas would be ideal.

 

[EdKuhn]

The hollow areas in ladders can be problematic. Over time, drains can accumulate muck underneath the cover that becomes a breeding ground for algae. Being sure of each of those areas would be ideal.

I'm just reading here about how to remove the drain cover. It's white plastic, I don't see any screws so I guess it snaps in place. I'll have to research how to remove it. Thanks, I'll keep hunting.

 

[EdKuhn]

The hollow areas in ladders can be problematic. Over time, drains can accumulate muck underneath the cover that becomes a breeding ground for algae. Being sure of each of those areas would be ideal.

Update. Last weekend I removed the drain cover and didn't really see any muck or anything. There wasn't much flow (or any really) into the drain so I got a drain pipe snake and pushed it in as far as I could (working underwater isn't fun btw). That seemed to improve the flow through the drain. Earlier this week kept seeing dead algae slowly collecting so I removed the light again from the niche and brushed deep inside where the wiring goes into the wall. Saw some blackish stuff fluff out. Last night I removed the ladder completely, SLAMed and this morning passed OCLT! So I guess it was the ladder or the very back of the niche. I will figure out a way to clean the inside of the ladder better. Thanks again for your help!

 

[Texas Splash]

Last night I removed the ladder completely, SLAMed and this morning passed OCLT!

Outstanding! Well done.