The green mile

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ccronje

Member
Dec 12, 2012
11
Johannesburg, SA
Hi All,

I'm hoping someone can give me some advice on this.

I have a small 15,000 liter in ground fiberglass pool that used to have nice and clear water, then 2 weeks ago we had some rain, the water turned green and I've been battling to get it clear again since then. Unfortunately I can't find any proper test kits in this country, so I'm basically down to guess work with a common 4-in-1 test kit from the pool shop.

Here's what I've done so far -

- Increased PH from 6.8 to 7.4
- Drained and replaced water to reduce CYA from 100+ to 60
- Last night I added enough bleach to bring the free chlorine up from 0ppm to the shock level of at least 24ppm as per pool school. This morning the water is still green, but a lighter shade of green and slightly clearer.

The test kits available here only measure FC up to 10ppm, so it's impossible to do an accurate OCLT test or to keep my FC constantly at shock level. The only thing my test kit tells me is that the FC is still above 10ppm.

Can anyone suggest a good way to proceed in the absence of a proper test kit?

With this basic kit I can at least see when the FC is between 7 and 10ppm, so if I let the FC come down now and keep it around 7-10ppm, will the algae eventually die out or will the chlorine fight a losing battle?

Thanks in advance for your help!

Chris
 
Yeah, that's going to be a tough one. I would try to solve it by......

When you are in the shock process, dilute your Pool sample with 50% chlorine-free water. It will give you a result that is not very accurate and you will not be able to do the OCLT but I think you can work around it.

1. Since your Shock value for a CYA of 60 is 24, use a value of 20-28ppm for your shock level. Even with the dilution and subsequent inaccuracy, I believe that will work for you.

3. Disregard the "real" OCLT and simply assume you are done with the shock process when your pool is crystal clear and you APPARENTLY do not lose more than 1ppm overnight. That may not be perfect but I think it will work.

4.
will the algae eventually die out or will the chlorine fight a losing battle?
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Don't let it go back to 5-7ppm until your pool is crystal clear and you pass that "makeshift" OCLT
 
ccronje said:
Thanks for the advice. It looks like that one shock did the trick. After I made this post the water started clearing up and 24 hours after I added all the bleach the water was as blue and clear as I haven't seen it in months!
Click to expand...
Don't stop now. Finish the shocking process or as soon as you turn your back on the pool it's gonna green up again.
 
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