Chlorine and Algae problems

[Sherry_R]

We bought our house last year and my project has been our pool. It seems I'm failing. I bought the test kit (TF-100) as suggested on this site and here are my readings:

FC - 0 (didn't even turn pink when I put the powder in)
CC - .5
PH - 7.5
TA - 120
CH - 170
CYA - 30

When we opened the pool this year, we had some yahoo do it. He incorrectly told us how to maintain a DE filter and we have since been doing it correctly. After backwashing and fixing the DE issue I was able to have a good chlorine level. It dropped off quickly and I have never been able to keep the chlorine level up. I had my husband try the backwashing trick again to no avail. The water has been clear and only slightly aqua at times, but a dose of chlorine (granular) it would go away. However, the bottom of the pool in the shallow end (where it becomes shaded quicker) has black spots (black algae?) I'm guessing algae is our problem with the chlorine (not sunlight) and I have not chlorinated it enough initially or correctly (bleach). Please help. I'm new to this but will follow your instructions and re-read and re-read all the Pool School stuff I need to. I really appreciate the help!

Sherry

 

[Bama Rambler]

Add enough to get you to 5 or 6 ppm and test in an hour to see if it holds.
Tonight add enough chlorine to get to 6 and test it after the sun goes down and run the OCLT tonight to see what's going on. I'm pretty sure it's going to need shocking.
Post back tonight's and tomorrow morning's readings and we'll help clear this up.

 

[Sherry_R]

Here's my numbers at night:

FC - .5
CC - 1.5
PH - 7.5
TA - 120
CH - 170
CYA - 30

And in the morning:

FC - 0
CC - 1
PH - 7.5
TA - 120
CH - 170
CYA - 20

I'm assuming shock time? Any other tips?

Again, thanks so much for your help!!

Sherry

 

[Beamup]

Was that really 0.5 in the evening, or 5.0? If the former, then you didn't have enough to start with for a proper OCLT - as Bama said, get it up to 5-6 for the starting point. If the latter, you lost 4.5 ppm and definitely need to shock, esp. combined with 1.5 ppm CC.

 

[Sherry_R]

It was .5. After attempting to get to 6 the chlorine wasn't holding. Do I need to shock to try and get me up to the right level then do the overnight loss test?

 

[Beamup]

Do you mean that you add a couple gallons of bleach, test half an hour later, and the FC reads 0.5?

 

[Sherry_R]

Yes. Adding 300ish oz of bleach did little after an hour (was 0) and brought to .5. Added 245 oz after that (per pool calculator) and no increase. Then let sit overnight.

 

[Beamup]

Definitely sounds like you need to shock, but with it getting consumed THAT fast you're probably going to need a lot of bleach.

 

[Bama Rambler]

Ditto on the lot of bleach. And you need to test and add every hour until you start holding FC.

 

[Sherry_R]

I'm on day 2 of shocking and while I failed the overnight test last night (FC 11, night; FC .5, morning), my intervals of adding boatloads of bleach are going down, so I'm hopeful. I know this is going to take a bit more time, but I was wondering if anyone can identify the black spots on the bottom of my pool (see pic). I'm assuming algae and eventually the bleach will kill this off. Is this a safe assumption??

 

[frogabog]

Have you tried brushing them?

 

[Sherry_R]

Yes, I've always brushed regularly. Did about 5 times yesterday. Once today. It's not moving or even flaking a bit.

 

[frogabog]

I think you can try rubbing a chlorine tablet on it. If it fades, it's algae.