Never had green algae on pool sides before

[millspap]

We were away for vacation and came back to green algae on the south pool sides. The pool water is clear. I know I probably need to shock the pool but I am not sure I am using your charts correctly. It is 7600 gallon pool and I have been using bleach when needed. Most recent other addition was 1 1/2 baking soda. I did the pool math and it said I needed 11 oz of 8.25% bleach and 6.3 oz of muriatic acid. I don't really understand if that is a SLAM?

Temp 72
Free chlorine 1
Combined Cl 1.5
pH 7.6
TA 100
CH 110
CA 80

 

[mknauss]

A SLAM is a process. See this article - Pool School - SLAM - Shock Level And Maintain

You must have a FAS-DPD test kit for FC testing. Your FC at shock level during a SLAM will be 32 ppm if your 'CA' is really CYA and it is at 80.
You can order just the FAS-DPD test kit from TFTestkits.net.

Until you get your test kit, add 3 qts of bleach to the pool each day to keep things from getting worse.

Take care.

 

[millspap]

Thank you, Marty. I had read the Pool School SLAM article but didn't realize that the test kit I had wouldn't do. I have ordered the FAS-DPD test kit. When I do the SLAM process, do I need to not swim in the pool during those days? I will probably be back with more questions once I get the kit.

 

[mknauss]

You can safely swim in your pool with the FC at or below shock level; you can see the bottom of the deep end; and your pH is between 7.2 and 7.8

You might want to consider draining and replacing some of your water. A CYA of 80 is not real easy to SLAM. With your small pool volume, I would drain half and refill it.

Take care.

 

[millspap]

Marty,

The FAS-DPD test kit came and these are my current readings.
Temp 68
Free Chlorine -4.6
Combined CL -.2
pH -8
Alkalinity -100
Calcium Hardness -110
Cyanuric Acid-70

I am reluctant to drain any of the pool because we live in the country and have iron in our well water. When we fill the pool in the spring, it takes me several days using a homemade filter to get the pool from coffee to clear.

I am going to read the Pool School SLAM article again and see if it makes sense now.

Thanks for your help.

 

[mknauss]

I understand on not wanting to drain. You can SLAM this, but need to stock up on bleach and be sure you have plenty of testing reagents.

Use a 10 ml water sample for your normal FC testing. One scoop of powder. Count number of drops and multiply by 0.5.

Prior to SLAM lower your pH to 7.2 with muriatic acid.

For FC testing during the SLAM (but not for a OCLT which you will do at the end of the SLAM) use a 5 ml sample and the number of drops to clear is your FC in ppm
It is best to get a 5 ml measuring device from a pharmacy. They have them for giving liquid medicines.

Keep asking questions.

 

[millspap]

Marty,
I finally got the free chlorine up to where it is supposed to be for SLAM. I need to get algae off the sides again. Once I can not see any green any where, do I go on to the OCLT?
Pam

 

[mknauss]

Do a Overnight Chlorine Loss Test when your pool water is crystal clear and you no longer have dead algae on the pool bottom. If you brush and 'wispy' stuff is there, that is dead algae.

Here is a clear pool -- TFP Clear in North Dallas - there is water in there

Take care.