Balancing pool water

[Gardenmom]

Hi, I am the pool mom. For 30 years I have ( successfully??) used the chlorine pucks, test strips or a 2 part drop test. I thought I was doing pretty good! Just last week my granddaughter began complaining about burning eyes. But the pool is crystal clear, my readings were a bit high, except for pH, which was low. So, I researched and ordered the Taylor K-2005C kit. Here are the results:

FC 15ppm
TC 15ppm
CC -0
pH- 7.2
TA- 150ppm
CH- 50 ppm
CYA-100 ppm

We have shocked weekly for 3 weeks as we went on vacations. From what I see, the FC and TC are high, and the CYA is very high. I have few teeny tiny black dots on the liner that may be black algae? So, how do I lower the chlorine and CYA? And should I use a copper based algicide for those pesky dots? We are going away for another week- dare I use the pucks?

 

[pooldv]

Do not use copper algaecide, the copper will accumulate in the pool and stain the water, pool, hair, fingernails, dogs, etc. Lots of people spend a lot of time and money trying get to remove metals and Metal Stains from their pools.

The only way to lower CYA is a partial drain of the pool. The problem is the CYA test only reads to 100, it could be much higher than that. You can do a diluted test to see if it is higher than 100, more here Pool School - Extended Test Kit Directions.

Pucks will add more CYA.

Do a little reading in Pool School
Start here, ABCs of Pool Water Chemistry
And here, Pool School - Getting Started

 

[Gardenmom]

Thank you. I will do the diluted CYA test. I suspect it is above 100. What do you recommend for the black (algae) dots? I think it may be spreading. I started brushing them more often. They are only on the bottom, in the shaded areas. One pool store said not black algae- doesn't grow on vinyl liners. Another store sold me 10 gallons chlorine and told me to add it all at once. ( which I didn't as I was afraid it would be too much, just added 5 gallons.) Oh, I also have a gorilla pad and wall liner under the liner. The liner was replaced in 2014 as we had to replace a rusted out skimmer panel. Don't know if that matters.

 

[pooldv]

More about how to treat black algae here, Pool School - Black Algae

 

[Gardenmom]

Ok. I went to one of my pool stores. ( The other store out of test discs.) He ran a drip strip computer read test. His vs My results today:

His
FC/TC >10ppm, he could only test to 10
PH "Good"
TA "Low"
CYA 130

Mine
FC/TC 10 ppm, down from yesterday, removed puck and solar blanket
pH 7.6, raised yesterday using "UP"
TA 170ppm
CYA 130-140 diluted test, ran twice


So our values are close. However, he told me I shouldn't be swimming AT ALL in that high of FC/TC. Is that true? Told me NO chlorine at all until value comes down to 5. I mentioned giving up pucks and start using the gallons of chlorine. He said, " You mean liquid shock." I said,"The liquid chlorine you sell in gallons." He replied, " Liquid shock." Is that one and the same? As we are leaving for a week tomorrow, if no chlorine is added, will we come home to an Olympic green pool? We were going to shock it tonight.
I read the Pool School articles as you indicated. We are going to try and wait til seasons end before partial drain. According to the black algae article, it also indicates not an issue on vinyl liners. I will try the fingernail test as soon as storms pass. Will the trichlor puck scrub damage the liner? Will try to attach pix of dots.

 

[Gardenmom]

Picture of dots, you may have to enlarge.

 

[jeffchap]

Liquid chlorine, liquid shock, bleach - all the same thing, sodium hypochlorite.



The pool store guy's lack of understanding of the FC/CYA relationship is precisely why they tend to mess up more pools than they fix. It is perfectly safe to swim with FC up to 40% of your CYA level. So *if* your CYA really is 130, then you are okay to swim up to a FC level of 52 ppm.



Now I say *if*, because CYA is one of the tests that pools stores are the worst at.

 

[Gardenmom]

Thanks. Yes, my CYA is at 130, I have received this result over 4 days using the Taylor K-2005c kit, including 2 samples using the dilution method. My FC and TC were at 15 ppm, lowered by removing puck and solar blanket. However, now I wonder whether I should maintain the high chlorine levels until we can do the partial drain. Pool store guy made me nervous as my grandkids love to swim for hours in the pool. Should I keep the chlorine up and shock it as we will be gone for a week?

 

[jeffchap]

With CYA at 130, your FC target is 14 and your minimum is 10. If you're going to be gone for a week, I'd bring it up to at least 40 before you go. That way if you lose 4 ppm per day to sunlight, you'll still be above the minimum when you return.

Don't worry, the pool is perfectly safe for your grandkids.

 

[Gardenmom]

Ok, thanks! I appreciate all the great advice and assistance. I am just learning after 30 years of pool ownership! Will shock!