Should I shock my pool?

[Woodberg]

My water looks very clear, and my numbers seem fine, but I noticed 2 small spots of algae (green color) on the wall in the deep end of my pool. They were both about the size of a frisbee and I could easily brush them off. Right now I'm losing about 1 ppm of chlorine at night and about 2-3 during the day. CC hovers between 0 and .5. I've got a lot of kids in the pool, which I'm sure is contributing to the higher chlorine usage during the day. Also a lot of direct sun. From what I've read on this site, I should not need to shock the pool, but yet this algae has popped up. If I do shock it, should I just take the chlorine level up to 20 overnight?

FC - 3 (was 6 this morning, I'm added bleach tonight)
CC - .5
PH - 7.6
TA - 100
CH - 240
CYA - 50

 

[frustratedpoolmom]

How often and when do you run your pump?

 

[Woodberg]

I run my pump 12 hours per day, 7:00am-7:00pm. I also have a separate pump which runs my in-floor cleaning system for 3 hours per day. The spot where I have the algae is in a corner and I can tell it doesn't get a lot of circulation because that's the one place in the pool that the in-floor system doesn't clean well.

 

[frustratedpoolmom]

I'd just give that spot extra brushing attention for a few days, up the FC 1-2ppm for a couple days and see if that takes care of it, and then give that area more attention with routine brushing in the future. 12 hours should be plenty, but if it is poor circulation in the area you can get FC dead zones. You're earlier posts did mention red eyes, so something is going on in the pool. If you don't notice an improvement in 2-3 days I'd assume a connection and go ahead and shock.

 

[Woodberg]

Thanks for the reply. I'll give that a try. Is it normal to have a spot like that in a pool where algae tends to grow easier?

 

[frustratedpoolmom]

Sure, if there is localized poor circulation, like in AGP wedding cake steps, for example. You can get FC dead spots, where all the FC in that one spot is consumed, and without good circulation to replenish it, Algae can take hold. Sounds like you don't have good circulation there, can you aim a return that way?

 

[Woodberg]

There actually is a return right by the algae spot, but with the in-floor system, the returns all point down toward the main drain. I could probably adjust it some, but the idea is to create a flow toward the main drain to direct any debris to the bottom of the pool. I'll keep an eye on this spot and brush it more often. Thanks for the help. It sounds like you've got your pool well under control. Mine is looking ok, but I'm still not too confident yet.

 

[frustratedpoolmom]

Aw heck, we were all noobs once. I didn't get my username by accident.

 

[JasonLion]

You might want to experiment with pointing all of the returns down and to the right (or left if you want, but all the same). Better yet, if you have enough returns, point one slightly up and to the side and the rest down and to the side. That should improve your circulation noticeably.

 

[Woodberg]

So I went ahead and shocked my pool last night. I raised the FC to 20 about 9:00 last night after the sun had gone down. I got up this morning and checked it before the sun came up and FC was 16. The pool is crystal clear. At a FC level of 20, is it reasonable to have lost 4 ppm of chlorine during the night or should it have held steady? We had a lot of kids in the pool on Sunday so I'm assuming that may be what the chlorine is attacking.

 

[ideliver]

if you lost 4 ppm overnight...you have an organic in your pool...you should hold at "shock level" (based on current CYA) until your FC drop overnight is neglible...

 

[Woodberg]

I know if my FC is at the target level for my CYA and the FC drops more than 1ppm during the night, then I should shock the pool. In my case, my FC was only dropping by .5-1ppm during the night. It was only last night, after I shocked the pool, that I had a larger FC drop during the night.

My question is if the shock level of 20ppm was so high, that as a percentage, a 4ppm drop during the night was acceptable. What I was thinking I should do, is do the nighttime FC drop test again tonight but at normal FC level, not at shock level. I'm at work now, but I'm assuming that the FC will have dropped considerably today during the day. If FC holds steady tonight, then I should be OK.

Does this even make sense, or should I keep the pool at shock level until it can hold a FC level of 20 without loss overnight?

 

[JasonLion]

No, that doesn't make sense. During the day you lose a percentage of your chlorine, but overnight you should not be losing any chlorine at all.

 

[Woodberg]

OK, that's what I wasn't understanding. I'll take it back up to shock level and keep it there until it holds overnight. Thanks.

 

[Woodberg]

I got my FC back up to shock level last night and it held steady this morning. Thanks for everyone's help, the water looks great. I took a couple of pictures of the pool and spa bottom last night with the lights on. The water was so clear you could see the trowel marks where they finished the Pebblesheen. I'll have to do something about that leaf in the pool.

[attachment=1:2cstczic]Spa.jpg[/attachment:2cstczic]

[attachment=0:2cstczic]Pool Bottom.jpg[/attachment:2cstczic]

 

[frustratedpoolmom]

WOW!

Yes, tend to that leaf RIGHT AWAY!!!!