I've had my new in-ground pool running now since February. We had no problems with it but at some point in maybe July, we had run out of Chlorine for possible a day or slightly more. We saw some algae forming around the waterfalls and a little bit below the water in the plaster.
No big deal, we shocked it. 10ppm and some scrubbing and a few hours and it was all gone. Great.
But it looked like it left a stain near the waterfall and also near the scupper.
It is all limestone block so we scraped it away and it was back to white. Great.
But it has come back. And it keeps happening.
We have usually 2.5ppm of CL in our pool at all times but what my theory is is that the scupper and waterfalls are getting moisture near them (not in them where the water flows out but around the edges) and they are not getting water on them in enough quantity to provide the CL. But it is damp enough I guess for algae to form.
We have been splashing it with Chlorinated pool water and scraping it off when it re-appears, but it keeps coming back in those two spots. Also if you let it sit like 5-7 days, it turns slightly blackish, like it is developing mold on the (dead?) algae.
I can't seem to find any way to make my scupper or waterfall behave differently. Water trickles out of it from all possible crevices at the opening, and it jut happens to run along part of the wall (raised beam). That is where the algae seems to want to grow. I guess because it is damp but does not have enough CL.
What can I do?
Do I need some kind of algacide? Will that kill it and prevent it from coming back or am I screwed or what???
Also, is it possible that I have algae in my filter? Or in the back of my scupper now because of that one time with no CL? I mean, I would imagine the inside of both would be quite moist/damp all the time, and if a little algae could have grown, it could still be growing.. Wait, doesn't algae need sunlight to grow? What about mold though? Oh man, I'm afraid to think what I will find next time I clean my pump. Hopefully nothing but some dirt, but ya never know...
Thanks in advance,