Need quick confirmation that I'm dealing with iron

[jenmenke]

Hi all,

Longtime user of pool forum. Very grateful for it. Have used BBB method for many years now and this is probably my first real problem.

We replaced our liner this spring and, rather than deal with what we went thru with our first pool fill, we bought balanced chlorinated water. Due to the EXTREME heat in Minnesota this year, I've done a fair amount of filling the pool with our well water. I use a spigot that runs through our softener, but there is most certainly still iron in the water.

For the past couple weeks, I have had to regularly brush the sides and floor of the pool because there are areas of what appears to be an orange/brown algae. It goes away for a day or two after I brush it. I have brought the water up to 12-15 ppm 2x now, but the orange areas show up right on cue a day or two later.

Is this iron? If so, will it eventually stop? Or if I manually vacuum it out with it be gone? I did not have this problem before this year. all my other numbers are good: PH 7.6, CL 1-3, ALK 150, CYA 50

thanks!

[PoolDoc]

Put a little granular chlorine on a spot.

If it's mustard algae, the chlorine will kill it. If it's iron, it won't have much effect.

[jenmenke]

there are no "spots". I can easily brush the orange away -- it acts like algae. A little slick/slimy if you run your hand over it, but it disappears in a cloud. But if it WERE algae, I'd assume my chlorine regimen would have gotten rid of it.

[PoolDoc]

But if it WERE algae, I'd assume my chlorine regimen would have gotten rid of it.

Mustard algae can be chlorine resistant.

Do the Pool Chart; do the chlorine test I mentioned.

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[jenmenke]

I did do the pool chart. Odd. I guess I'll do it again

[jenmenke]

Mustard algae can be chlorine resistant.

Do the Pool Chart; do the chlorine test I mentioned.
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I'm not sure I understand: you mean sprinkle granular chlorine on to the wispy, easily brushed away orange and then try really hard not to disturb it? Since I only use bleach, I don't have any granular chlorine. Can I crush up a puck? I think I have a few of those. Let me know

[PoolDoc]

I hadn't looked for your chart; I will. If it was there, it still is.

But, a small piece of trichlor will work fine. You can lower it into place with a thread. Just don't leave it there overnight, or anything like that.

[jenmenke]

OK. I put a tricolor tablet directly on top of a corner that had some orange starting to show and two hours later it was mostly gone. So that's algae, and not iron, right? So now what? My guess would be that I didn't keep the chlorine ppm high enough for long enough?

[PoolDoc]

You are correct.

Mustard algae can be eliminated by brushing + very high chlorine, and then continuing high chlorine and brushing after it all seems to be gone.

[jenmenke]

So what is "really high chlorine" for CYA 45 water temp 85?

[PoolDoc]

I'd probably start with 20 ppm (50% of CYA) and see if that works.

[jenmenke]

Ah! Now I get it: 50% of the CYA number is the shock level. thanks for saying that.

Here is an odd thing: I'd had the orange stuff on bottom and corners for a couple weeks before I posted here. Brushed, vacuumed, etc. Did one shock treatment, but only brought the chlorine to 15. Orange showed up again and then I posted, as I thought it might be iron. After doing your test with the trichlor tab in the corner where orange was, it all disappeared. No more evidence of orange. That was -- what -- 4 or 5 days ago? I have yet to see anything come back -- and I never shocked again.

Isn't that weird? I'm still waiting for it to re-appear... But don't you think I should wait before dumping all that chlorine in if I don't have to? The water looks perfect...

[PoolDoc]

50% of CYA is usually higher than you have to go.

But, mustard algae is tricky -- I'd recommend holding chlorine at a higher than normal level AND CONTINUING TO BRUSH regularly for at least a week after you think it's all gone.