At wits end: Algae buildup

[fnyman66]

So i am at my wits end and have no idea what i am doing wrong. So far this year, I absolutely can't get rid of algae an i feel like i have tried everything. I started to notice some algae on the walls of the deep end in the sun so i thought i would nip it in the bud. I tried slamming the pool for several days and felt like it was getting better but it really wasn't. I started to think that it might be a calcium buildup since mine was pretty high. That led me to try and lower the pH while keeping the chlorine pretty high and try to brush the buildup off with a wire brush. Still no go! I have been consistent with brushing each day and staying on top of the chlorine but i am at the end of my rope. Please provide some help because i want to just fill the pool in.

This pool is not the best design and is too simple of a design. Only one skimmer for 28,000 gallons but i have added a robotic cleaner and a skimmer on one of the returns. Lastly, I live in Dallas, TX and it is beginning to warm so i am concerned about trying to empty and refill the pool.

FC - 11
pH - 7.4
TA - 100
CH - 625 (used cal-hypo to slam)
CYA - 65

 

[fnyman66]

 

[woodyp]

Pool School - Chlorine / CYA Chart that chart your SLAM level should 28 for your CYA level. 11 won't get you there. How are you testing?

 

[JohnT]

Algae should come off easily with a wire brush. Maybe metal staining? Ever use algaecide or have a heater fail?

 

[Jimrahbe]

fny,

If you are SLAMing your FC is waaaay too low for your CYA level.. With a CYA of 65 (rounded up to 70) your FC needs to be about 28 to get rid of algae..

See this chart... https://www.troublefreepool.com/content/128-chlorine-cya-chart-slam-shock

Just so I can make sure we are all on the same page, what do you normally use to chlorinate your pool? And what test kit are you using to get the results you posted?

Here are the instructions on how to SLAM a pool.... https://www.troublefreepool.com/content/125-slam-shock-level-and-maintain-shockingl

When you brush this "algae" does it just go poof and go everywhere like dust, or not. I am by far not an expert in this area, but it looks more that a stain or scaling issue in the pics..

Let's see if we can get opinions from some of our other members...

Thanks,

Jim R.

 

[fnyman66]

I am not still slamming the pool but had previously done it and knew what level to do. My pool has no heater and I have never tried algaecide. Using a wire brush takes a minimal amount but I have tried brushing to no avail. I have wondered if it was some stain or scale but I don't even know where to begin with it.

 

[pooldv]

If you have passed the 3 SLAM criteria then you can try diagnosing the stains here, Pool School - Pool Stains

 

[domct203]

I also think that may be staining.

What does the OCLT tell you?

What test kit do you use?

 

[fnyman66]

I use the TF-100 test kit for my pool testing. I have no heater or any metal in the pool and the water is not from a ground well. Is there another way to test organic stains besides holding a puck to it? I don't have any and definitely don't want to purchase any. What is OCLT?

 

[spinPHD]

OCLT is Overnight Chlorine Loss Test. Test your FC levels after sun goes down. Then test it again in morning before it comes up. If you lose more than 1 of FC, then you need to keep SLAMing

 

[satpoolman]

If you have passed the 3 SLAM criteria then you can try diagnosing the stains here, Pool School - Pool Stains

This would be my next step.

From looking at your pics, it looks like you have some scale that has absorbed some sort of mineral/metal to give it that coloring.

Eric

 

[fnyman66]

I did the OCLT and there was no change in FC. The water is very clear and the stains are unchanged. I am going to get vitamin C to test for iron next because I have not copper in my pool system.

 

[borjis]

I have no metals in my water source either, but had some iron (water turned green ish) out of now where when I added
chlorine the first day this year. It can occur even if it makes no sense. So I roughly replaced half the water
and the water turned clear again.

It does sound like some sort of metal staining, but I could be wrong.

At least you don't have to slam.

 

[abycat]

I thought it was algae but i guess not. Good luck with fixing the stain!

 

[jeffbrig]

I dunno. That looks an awful lot like the algae I've battled in my pool. Water column is perfectly clear - it only grows on the sides (less sun), disappears with elevated FC, comes back at recommended FC target. Even with aggressive brushing, a little brushes off (you seen a tiny algae colored cloud), but the plaster does not fully come clean even with hard scrubbing.

People are telling me it sounds like mustard algae. FWIW, I completed a slam recently, and then did 24 hours at elevated Mustard Algae shock level. Still didn't eradicate it - started reappearing a few days later at target FC. I think I've resigned myself that I'll need to hold FC towards the upper end of the recommended range to keep it at bay, as it seems immune to normal FC.

 

[fnyman66]

Well, I tried the Vitamin C trick to check for iron and I would say the results are inconclusive. It looked like it faded some, but it did not disappear so I still don't know. My situation sounds a lot like Jeff's. It fades slightly during slamming but gets dark when the pool is held at target FC. I am close to giving up and calling a pool service to see what can be done.

 

[JohnT]

Pool company is probably going to suggest an acid wash, so you want to do everything possible to resolve it yourself. Obviously pictures are a hard way to diagnose, so most of what we are doing is guessing and trying to guide you through identifying the issue.

Does the stained area feel different from the rest of the plaster? Smoother or rougher? Smoother might indicate the plaster is thin or gone, while rougher might indicate calcium scaling. Calcium scaling will stain which can make it hard to recognize.

To determine if you have an organic stain place a trichlor puck on the stain for a few minutes to see if it lightens or removes the stain.