Persistent Stains After Algae

[botloveslights]

Hi there, I'm a new home and pool owner. I was trying to figure all this out on my own before I recently found TFP. Long story short, I had algae and got rid of it, but have leftover stains that I can’t get seem to get out.

1. Where I started - not knowing anything and using test strips before discovering TFP

• I went out of town for a few weeks and came back to some algae all over the pool but mostly on the shaded side
• I shocked the pool with granules (with CYA, before I learned that I should use liquid chlorine) and thankfully brushed most of the algae off pretty easily, but now there were stains that were left behind
• I shocked the pool again a few days later and kept brushing the pool for over a week but with no luck

2. What I tried - after discovering TFP/Pool Math and getting my TF-Pro test kit

• Levels: pH: 7.8 | FC: 13 | CC: 0.5 | CYA: 100 | TA: 110 | CH: 350
• Put a trichlor tablet on a stain for a few minutes to confirm if it was organic, but there was no change. Not even with me scrubbing the tablet into the stain
• Crushed up vitamin C, put it into a skimmer sock, and put it on a stain to confirm if it was metal, but there was no change
• CYA was too high but I didn’t want to drain the pool just yet so I lowered the pH with muriatic acid and then did a SLAM for 3 days with 39 FC (followed Pool Math)
• Levels: pH: 7.2 | FC: 39 | CC: 0 | CYA: 100 | TA: 110 | CH: 350
• I used a stainless steel wire brush on the stains but it did nothing
• I also tried the Erase It stain erase for concrete and plaster pools. It worked on some very small stains (width of angel hair pasta / length of a needle or smaller) but took A LOT of elbow grease. It did nothing on the bigger stains

3. Where I am now - seeking help

• Yesterday, I finally decided to drain and refill half of my pool (5k gallons) to reduce my CYA
• Levels: pH: 7.8 | FC: 10 | CC: 0.5 | CYA: 40 | TA: 120 | CH: 425

Pool Math says to target 16 FC if I want to SLAM, but I'm hoping to get some advice before I do anything else. What should I do now? I'm kind of at my wit's end. The pool plaster used to be perfect and blue, and now it looks awful. Any help would be much appreciated! Thanks in advance!

 

[mknauss]

Welcome to the forum.
Are the stains rough or smooth?
Do you have some dry acid? If so, put some in a sock and set it on the stain for a few minutes.
Otherwise, get a stain ID kit from Jacks Magic.
Tell us some history, you do not show a heater, you do not have one?
How have you been chlorinating?
Any copper based algaecides?

 

[botloveslights]

Thank you so much for the warm welcome and for the quick response!

• The stains are rough
• I don't have dry acid, but I will get some and try it out. If this works, what does that mean?
• I don't have a heater
• I was chlorinating with trichlor pucks up until a few weeks ago (before I found TFP) and have been using 10% liquid chlorine since then
• I haven't used any algaecides

 

[mknauss]

If the stains are rough, then it is likely calcium embedded with dirt. Doubt you need the dry acid, that is a cheap way to test for copper. You should not have copper unless you used trichlor pucks that had it in it. Costco tabs are notorious for that.

So you need to decide how aggressive you want to be on this. Anything you do should likely be delayed until we get into winter.

 

[botloveslights]

I was using pucks from the pool store that shall not be named.

I'll do some research on calcium stains now. Thanks for pointing me in the right direction!

 

[botloveslights]

@mknauss Could you elaborate on "decide how aggressive" I want to be?

 

[mknauss]

You can leave it as is. Maybe run a low CSI to see if that removes some scale.
You can hire a company to drain the pool and acid wash. Very commonly done in our area. Not advised. But done quite often.
You can try a product that you add to the water and monitor for a day or two, then drain and refill. Might help, might not.
You can hire a company to chip out and replaster. The perfect method. But costly.

 

[botloveslights]

Got it. That really did cover the spectrum of not aggressive to aggressive Thank you so much!

I think I'll try low CSI first. What would you do if it was your pool? I doubt you would have this problem in the first place though!