Water looks clear and sparkly, but...

[eskewj]

I’ve been drawing water out of our pool and refilling, over the course of several sessions (never going completely empty to prevent pop out) in an attempt to get my CYA to a manageable level. Previous owner had been using the pucks for a decade or so and had never replaced water.

I’m now down to about 60ppm CYA so I’m thinking I will stop here and try to balance and maintain. Overnight there was what I *think* was a little bit of algae sprouting along the vinyl seams, even though I’ve been circulating non-stop. I went out and swept it away with the pool brush, but it returned a few hours later. I’m thinking I need to do something urgently to prevent a swamp from forming as I haven’t added any chemicals at all in the short time I’ve owned the pool.

Here are my numbers:
CYA = 60
FC = 4.5
CC = Not present
pH = 7.4
TA = 160 ppm
CH = 120 ppm

According to Pool Math, I need to add a little over half a gallon of bleach to my 16,000 gallon pool to get the FC where it should be. Any comments are welcome! Thanks for your feedback.

 

[jblizzle]

IF you suspect algae starting you need to follow the SLAM Process until you pass the 3 criteria to stop ... which is going to require a lot more bleach that a half gallon.

This also requires that you have the FAS-DPD chlorine test that is part of the Recommended Test Kits (if you do not have it already).

 

[eskewj]

OK. I didn't have enough bleach on hand for a proper SLAM, but I added two gallons and will re-test tomorrow after 24hrs of circulation. Also brushed off the remaining algae again (it was only a small area) so we'll see if it returns.

 

[pwrstrk]

Get yourself some more bleach. The longer you maintain SLAM level the quicker this will go for you.

 

[jblizzle]

Please read the process ... it is not a one time addition of chlorine. Ideally you are testing and adding bleach as required every hour or so to start, but at LEAST twice a day.

 

[duraleigh]

SLAMming the pool hurts nothing and only helps.

That said, your test results would indicate your FC levels have been fluctuating a lot to allow algae to get a grip? If that's true, I would first try simply maintaining an FC around 10 ppm and CONSTANTLY REPLENISHING to hold FC at 10 for a few days and see if the algae is eliminated

 

[eskewj]

Just an update...I held off on SLAMing because I was on the fence about draining again to get my CYA levels down just a little more. Basically, I didn't want all my bleach to go down the drain and also did not want to try to balance twice. Plus it is winter here and nobody is using the pool. I ended up replacing some water and that helped to get CYA where I am happy with it.

Here are my new numbers:
pH: 8.0
TA: 140 ppm
CH: 120 ppm
CYA: 30 ppm
FC: 4.5
CC: 0

What I think I should do first is balance the pH by adding muriatic acid and this should also have an effect on TA. From reading here, I should not worry about my CH number even though it isn't quite in the suggested range listed in the book from my test kit. After pH reads OK, then I can SLAM. Is this a good gameplan?

 

[pwrstrk]

Yes lower your PH into the low 7's if your going to SLAM. Needs to be lowered any how. Do you still have visible algae ? If your pool water is cold did you let your sample come to room temp before you did the CYA test. Sometimes cold water can affect the CYA test.

 

[eskewj]

I went to the pool store and they did not have muriatic acid (too dangerous?) so I got some sodium bisulfate to lower the pH instead. I didn't know about the cold impacting the CYA test...I will try it again at room temp.

 

[pwrstrk]

You can get the acid at HD, Lowe's.