Any reason to shock?

[salinda]

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.

[Rangeball]

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

[salinda]

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?

[Rangeball]

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.

[KurtV]

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.

[salinda]

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.

[leejp]

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

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.

[salinda]

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?