I picked up an Algae bloom (I think)

So up until last week the water was perfectly clear, I did notice the bottom felt slick, so it did cross my mind, but the numbers had been hold fine. Then the water began to get cloudy. I took new readings, had lower CL. I also found I had no CYA (?!). Prior to this I had added stabilizer and had a solid 40 reading. Nonetheless I had cloudy water and no CYA, so here I started with:
FC - 0
pH - 7.4
CYA - 0
Alk - 120

I began adding bleach (then switched to granular cal hypo) pushing my Cl to above 12. It's been four days and there has been no change in the water. What should I be doing?

thanks, herb
25 gal inground
gunite pool

Hi Herb:
Start by getting us a full readout of numbers and a description of your pool (gallons, vinyl or hard-sided,type of filter and pump). In the meantime keep up the chlorine.

Carl

My readings as of 8:00 am today are:
FC - 12
CC - 4.5
pH - 7.4
Alk - 120
CYA - 0
CH - 280
I have a 25K gal inground gunite pool with sand filter. Water is still cloudy, no improvement in calrity in five days.

How many times per day are you testing and shocking the pool back up? If your water is cloudy, I'd use bleach instead of cal-hypo. Bleach won't contribute to cloudy water problems, but cal-hypo can. Are you running your pump 24/7 and backwashing when there is a 5-10psi pressure rise over clean filter pressure?

With a CYA of 0, you need to keep your chlorine up there between 12-15 by testing and adding more chlorine as many times as possible during the day to maintain the 12-15 ppm. I personally would switch back to plain, unscented bleach--your calcium levels are going to rise substantially if you're using cal-hypo to shock, and once they get to 400 or so, you're going to start having milky water issues. Keep it high until the pool clears, and your CC goes to zero.

Keep the filter running 24/7 , brush the pool daily, watch your filter pressure and clean it as necessary.

When you had a CYA of 40, was that earlier this season? Or at the end of last season?

Edit: Looks like Watermom and I were posting at the same time....but the advice is the same!

This summer we've been seeing a number of pools with your condition. I think, given the high CC level and 0 CYA level that your CYA got converted to Ammonia compounds. It's going to take a lot of shocking with bleach or Liquid Chlorine to get it clear.

LUCKILY, with your pool, if you want to over-shock it (go above the recommended shock level) it won't hurt your pool at all. Those shock levels are the minimum levels and are safe for vinyl pools.

So if you want to blast your water 'way up into higher chlorine levels, it may clear it up faster. I THINK you need 7ppm of FC for every 1 of CC and that would mean a level of 31...I'm not certain. It should help.
However, two things I am certain of:
at that level of chlorine you shouldn't swim,
and it won't damage your pool.

If you can buy reusable carboys of 5 gallons of 12.5% liquid chlorine that can be easier to handle...one container is equal to 10 gallons of 6% bleach and then you return it like a deposit bottle. But if you do, be sure to get the spigot that goes on the carboy...makes life much easier.

Carl

The amount of FC to get rid of CC (if it's monochloramine) is only somewhat more than half the CC level. The 10x rule is wrong when applied to CC. If you measure ammonia levels, then it's at least 7.6 and normally 8-10x that ammonia-nitrogen level as FC to get rid of it. On top of that, there will be partially broken down CYA that doesn't measure as ammonia nor as CC.

Basically, just blast it with a lot of chlorine. If you want to predict how much will be needed, then do a bucket test and note that 1/4 teaspoon of 6% bleach in 2 gallons is 10 ppm FC.

It took all of two weeks, with a high CL (+20) and lots of back washing, but the water has finally cleared up. Thanks for the clear direction. It's great to have the advice,,,cause it can be very easy to panic and run off course with the treatment. BTW I stopped using the hypocl and went back to just belach. (I think that helped too) Thanks again.