Green Water: New to TFP, not new to Pools

[Dumello]

Hi All. I found this site over the weekend when trying to address a green water problem I've been fighting for at least 6 weeks. After reading this site, and taking my water in for testing, I have concluded that my primary issue is related to having a high CYA value of 90. I have been getting green water with very little algae on the pool walls. I would shock the pool with Cal Hypo bringing the FC up to 14. It would remove the green over 2-3 days, but the water would be slightly cloudy. I figured this was filtration, so I let FC drift back down to 4'ish. The pool would then quickly turn green again. Duh, I now know I need to maintain a FC of 10-12! I debated draining 1/2 my pool, but I have well water and would have to get water trucked in...big $, and not really an option. I'll address CYA when I lower my pool water at winterization and stop using chlorine pucks. That's the background, here's my question....

How quickly will the FC drop when my pool is green and I SLAM it to 30 FC with a CYA value of 90?

I dumped a truckload of 6% bleach in the pool last night and brought the FC up to 28-30. I check this morning and it's at 24+. I don't have a DPD-FAS testing kit yet...it's on the way...but I used my DPD testing kit by diluting the water with 3 parts distilled water to 1 part pool water. Maybe not exact....but tells me I'm at 24+. The water looks better, but still plenty of green and cloudiness, with lot's of dead stuff on the bottom of the pool.

I get that the CYA will hold the chlorine longer in the sun, but I didn't think it would stop the algae from consuming it. I also understand it will take longer for the chlorine to do its job, but is this what I should expect? Is there anything I should be doing differently? I'm worried that if I bring the FC back up to 30+ again it will be 2 weeks before I can swim again. I really expected the FC to drop dramatically last night.

Thanks for any help. I'm excited to be a part of this community and I look forward to a trouble free pool!

Jeff

 

[JVTrain]

Jeff-

Glad you've found TFP.

In truth, if your CYA is 90, it's safe to swim if the FC is less than the shock level for your CYA, which would be 35. It may be slightly harsher on your suits and skin, but it's still safe to swim below that level. You also should be able to clearly see the bottom and have the pH between 7.2 and 8.0 for safe swimming.

You're right, it will vary wildly how much FC you'll lose each day to sun and to an active algae issue but I've seen 50% losses per day easily, however this was at mid-teens shock levels not 30+.

The other problem you have with maintaining constant FC levels above 10 ppm due to high CYA is ability to accurately test your pH. At FC levels of 10 and above, the pH test is biased and not accurate. It will usually read higher than it actually is. The phenol red is affected by these high FC levels. So unless your FC drops below 10, you can't really test pH.

It would be more convenient to get the CYA to something closer to 60, which would be more manageable from a SLAM stand point and for being able to monitor pH more easily after SLAM is complete. Be sure to read through the SLAM procedure, the proven method that we use here at TFP to deal with algae (link in my signature).

 

[AftonJeeper]

Jeff, One thing that helped me when I was filling my pool, and when I top it off, is using a whole house water filter to get some of the larger iron particles out. In the year+ since my pool was installed I have not had any metal issues with my pool water but my dogs water bowl is brownish.

Hopefully that helps and you can lower your CYA with your water.