Struggling with Numbers in AZ

[Rasputin85]

I moved into a new home with my first pool in May. Around June/July I started to have problems with keeping my numbers within range. After reading on here a good deal and buying a DPD test kit, I slammed the pool and had it looking alright. In the last couple weeks it's been creeping back towards green. I used a Flocculant to see if that could help get some of the fine dust and debris out after a number of storms came through town. TC was around 3 and CC was less than .5. On 9/6/15, I put in about 1.5 lbs of Sodium Dichloro in the pool that's right around 15,000 gallons. That put the TC to 7.5. Now, 5 days later here are my numbers:
FC-~6
TC-6.5
pH-7.6
TA- 120ppm
CH- 440ppm
CYA- 75

I'd love to avoid draining half the pool if at all possible, but I just wanted to check and see if there was any other hope for me to bring down the CYA and CH another way.

Any my help is greatly appreciated!

 

[ozdiver]

To get rid of CYA you gotta do a partial drain.
Poolmath will let you know how much.
We need to know your pool details (pop them in your signature line)
Volume, Salt or Bleach, Plaster or Vinyl, Inground/Above Ground. That sort of stuff.

Let me make an educated guess, you are plaster and bleach.
That is why CYA 75 concerns you.
With that level you are growing algae whenever the FC drops below 6ppm.
Even when you bring it back up above 6, you have a potential problem brewing.

Can you perform an OCLT to determine if your pool is actively fighting an algae situation?

 

[Rasputin85]

Sorry for leaving out that information. Correct, it's an in ground, chlorine plaster pool. I haven't specifically completed an OCLT, but I feel like because it's only lost 1-1.5ppm since Sunday evening's shock dose, it's not fighting an algae bloom currently. I suppose at this point there's no option but to drain about 50% of the pool.

Thanks for for your input!!

 

[BuckeyeChris]

I think you are fine at cya 75, unless you really want to do a partial drain. Get one of the recommended test kits, verify your cya, and bring your FC level up to the required levels according to the CYA chart. Your initial dose might be high, but day to day, you'll use less than you would at 40 or 50. You'll also need a FAS-DPD to really get good FC reading at the higher levels.

the other levels are fine for now, as long as your CSI index isn't in scaling range. Put your numbers into pool math (tab at the top of the page).

- - - Updated - - -

also, there is really no way you've only lost 1.5ppm of chlorine since sunday. Shock levels of chlorine (active chlorine not bound to stabilizer) are totally exposed to UV. Now, your FC of 7 is no where near the shock level required for that CYA level, so 99% of your chlorine is bound to stabilizer. Still, 4+ days of UV exposure, plus killing algae, leads me to believe you have a crappy FC test.

 

[duraleigh]

Why do you think you need to drain 50% of your pool? A CYA of 75 is certainly high but does not require a 50% drain to be manageable. Tell us what you are thinking and we'll get you on the right track. Please test the CH of your fill water and post that, too. Tell us what your water looks like.

 

[Wildcat]

2 years ago my pool in Tucson was over 150 CYA. Kept doing partial drains, trying to time it with an approaching monsoon. I would drain down an inch or two, get some rain and top off what the rain didn't fill.
In the winter I drained 6-8 inches a few times. Anyway in about 16 months my CYA was down to 60, now at 50. During that time I just kept my FC at the high end or even a little above the recommended range for my CYA. No algae ever.

I think that with our intense sun and very few cloudy days I think it is wise to keep the CYA in the 50-60 range rather than the 20-40 often recommended here. You can live with 75 as duraleigh says. Just don't be casual about the FC level. Never ever ever let it drop below your minimum and I would err on the safe side. Chlorine levels up to SLAM level are safe to swim in so a FC of 10-12 is not going to hurt you ( you can use a little more chlorine at the higher level but that is the least of your concerns)


Oh, BTW, you do know that adding dichlor aggravated your CYA. Bleach (liquid chlorine) only from now on.