High CYA and Persistent Algae

[Watermom]

Just wanted to welcome you to the forum!

[bthoward]

Thanks! Just want to give an update and make sure I am following your advice correctly.

Sunday night I raised my chlorine level to 30ppm using bleach. I brushed and then vacuumed the pool and it looked great. I then tested the water again Monday fc=28, Tuesday fc=25. Today, I noticed that there are traces of algae on the pool walls. Ugh!

My water tests today:

FC=21
CC=0
PH=7.4
ALK=110
CH=600
CYA=100+

I am going to add more bleach and brush the sides again to hopefully knock it out for good. My filter pressure has not risen very much at all. Should I backwash anyways?

[PoolDoc]

Looks good to me . . . sorta.

Your saturation index (pH + alk + ch) is out of sight. Once you're ready to close for winter, you may want to do something about that -- but it will mess up your pool for awhile when you do, so now's not the time. Just be careful to NOT add any alkalinity (baking soda) or calcium (calcium chloride). And do NOT let your pH go up: hold it below 7.4.

Your chlorine is high enough, so that to get accurate pH readings, you'll need to mix pool water 50:50 with distilled (not: bottled!) water before testing. Make sure it's "distilled" -- usually available in the bottled water section at Walmart -- and NOT anything else.

Also, keep your chlorine high and brush the pool out at least 1 cycle AFTER you think all the algae is gone. Then, and not before, you can let your chlorine drop.

[bthoward]

First off, thanks for the continued advice. Just checking to see if I am following your instructions correctly.

I held the FC=25 and PH=7.4 for a week and there were little to no signs of any algae. The past couple of days I've let it drop to 21 and now there were signs of algae growing on the walls. Should I just brush and raise it back up past 25 again for a bit longer?

[aylad]

If you still have algae in the pool, then you need to raise it back up and hold it there, past the point where you think all the algae is gone. One good test for when to let it drop back down is when you can test at night after the sun is off the pool, and test again in the morning before the sun is on the pool, and see if you've lost chlorine overnight. If so, then you still have something in the water consuming it, so don't let it drift down yet.

Are you also putting any brushes, poles, pool toys, etc. in the pool while it's being shocked, to keep from re-introducing algae when you use them?

Might want to consider the use of Borates at 50 ppm, which acts as an algaecide and can be used in conjunction with regular shocking, HOWEVER, since Pooldoc has ponted out that you need to keep your pH low for now, I'll let him advise you on whether that might help in your situation.

Janet