Any reason to shock?

Here are my numbers today:
TC 4
FC 3.5 (in CC test, barely detectable pink disappeared in one drop, so CC could be less than .5)
ph 7.2-7.3
TA 100
CH 570
CYA 50
5620 salt

I had two swim parties this weekend. The water was slightly cloudy from each one but the first cleared in less than a day and after the second, I ran a timeout cycle on my pump during the night to filter the water for a while after the party and it is almost clear this morning.

Should you always shock after these parties? I have a large pool and so the bather load is not as heavy as in a smaller volume pool. I have never shocked before, but I read about others shocking after these things. We swim all week and I hate to send my kids into a 15-16 ppm FC pool, even with old suits.

No need to shock unless testing shows combined chlorine that doesn't clear overnight.

So, I ran my filter for 3 hours after the party and tested this AM. That is the test that showed a little (slight) CC. Should I wait a few hours more and test again? Does that slight CC merit shocking?

How are you testing? DPD? FAS/DPD?

If you are testing FAS/DPD using a 10ml sample, and the CC cleared with one drop, I wouldn't shock. If it took 2 drops, indicating CC was over .5 ppm, I'd let my pump circulate until I was sure I got one turnover and test again. If CC was still over .5 ppm, I'd shock.

I had kids in my pool all weekend. Woke up this morning, water is crystal clear with no CC. I just left the pump running the whole time to ensure good circulation and mixing, then turned it off this morning.

You can also just add a bit more chlorine in advance of pool parties to preclude problems. An extra 3-5 ppm won't hurt the suits or the kids(especially with 50 ppm CYA) and will probably keep the water from clouding. You'd need to add a little over 1.5 gallons (218 oz.) of 6% bleach to raise your FC by 3 ppm. That will also take a little strain off your SWG cell.

Rangeball and Kurt,

Thanks so much. I am a pool owner now for 3 years and a poolforum member for 2.5 and I am still learning....

I use the dpd test and I just got new powder, so it should be very accurate. The water is now absolutely clear. When I say a little cloudy, most would probably say it is clear. You can see the drain (10 feet deep), but not like you would see something in 2 feet of water. This afternoon it is crystal clear with NO cloudiness. I think some of the cloudiness is caused by sunscreen.

I picked up a 3 gallon pack of bleach at Costco last time I was there just in case....

Also, Rangeball made me realize I should just leave the pool on overnight after these events. I got a variable speed pump last year and I can run it at VERY low speeds if I am worried about energy.

Quote:

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Originally Posted by salinda

TC 4
FC 3.5 (in CC test, barely detectable pink disappeared in one drop, so CC could be less than .5)
ph 7.2-7.3
TA 100
CH 570
CYA 50
5620 salt

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Where do you generally run FC? With CYA @ 50 I run between 5~6PPM FC. Sometimes it slips to 7PPM FC. But running on the high end of the the CYA chart I've found no eye/skin irritation and absolutely no need to shock (have not found CC in my pool this year yet ;)). With heavy rain, debris, sun exposure, bather load... the FC slips to ~4PPM.

I think it's better to have a couple of pool parties and end the day with no CC vs even a tiny amount of CC.

I run the FC at around 4 ppm. My cya is actually much lower than recommended for the swg. I have read a lot of posts here over the years and, although I don't quite get it, with an swg you can run at lower FC's than the best guess table even with higher CYA levels. Here is one of the posts I am referring to:

http://www.poolforum.com/pf2/showthread.php?t=6929

Some people run with a much lower cya, but my pool was tending to get a couple of patches of algae with the lower cya.

Are you using a saltwater generator?