Simple questions on shocking...

Greetings,

Thanks in advance to those who answer my post. I have a 27,000 gallon salt water in ground pool with diamond brite plaster, opened in December, used moderately since spring. With the help of this forum, I've had decent luck with the upkeep. Average numbers are as follows:

Salt level 3200 ppm
Pool chlorinator @ 50% Spa @ 10%
Free Chlorine 2-3 ppm
PH 7.4-7.6 ppm
ALK 70-80
CH 370-390
CYA 40-55

I say average because the torrential rains here in Texas have had my numbers all over the map, but I pretty much end back up at the above data. I've noticed some SLIGHT light brown discoloration in spots that I think MAY be algae, but can't be sure. The water has been pretty clear for the most part. But on the fourth we had a party with about 20-25 swimming guests (including kids.) I have yet to shock this pool.

I've read different things on when to superchlorinate a pool, ranging from the difference between FC and CC, condition of water (cloudy etc.), bather load, timing, etc. I've also seen different takes on the amount of product to use, a percentage of your FC etc. I'm a little confused, though I am QUITE sure not to use my chlorinator and use a liquid chlorine instead.

Also, wifey wants to use the pool this weekend very badly. I'm concerned about letting her swim after the heavy use from this party, but also unsure when it will be safe to swim again after I shock it.

So... Questions are, how much product (and which brand) should I use? I know I need to keep it at a certain level for a certain time period. How long till the chlorine eventually dissipates, with all the rain we are having? Do I pour the chlorine evenly around the pool? Do I need to run the filter pump 24/7? I know I need to brush constantly, but when to start? What schedule should I get on for regaular shocking? Have I waited too long?

Lastly, my Leslie's test kit will only measure to 5ppm. Where can I find a kit to measure larger amounts of chlorine?

Thanks in advance to all you experts! I searched but could find no good threads dealing with my specific questions. Any links would also be appreciated.


Mike
Arlington, TX
(Land of the never ending low pressure front)

Hi, Mike,

You don't give combined chlorine numbers, but if you're getting small brown spots then it's definitely time to shock it. I would also shock it after a large bather load like your swim party. If it were my pool, I'd shock it to 15-20 using bleach (or liquid chlorine), and hold it there until the algae dies. This may require testing 2-3 times a day and adding more bleach to get back up to shock level, but it's the only thing that's going to kill your algae bloom for good. In the meantime, brush daily and run your pump/filter 24/7. Once the algae is dead, you can let your chlorine drift back down to your normal levels, but I would still keep a minimum of 4-5 ppm chlorine to make sure the algae problem doesn't come back. How long it will take for the chlorine to come down depends on whether or not you ever see sun again :eek: and any other organic load that's in your water...but I would say that on average, it wouldn't take mopre than 2-3 days for it to come back down, and it'll happen sooner in sunlight.

I am around Shreveport, LA, so we're getting hammered with it, too, and there's no telling what all the rain is introducing to the pool. It gets a little hard to manage if you don't stay on top of it, so I would go ahead and shock it now and try to keep it there for at least the next couple of days. When you add the bleach, you can pour it slowly in front of the return and let the jet help dispurse the bleach throughout the pool, or you can walk around the sides and dribble it in, stirring with a pool noodle or somthing to keep the bleach from concentrating in one area.

As for measuring chlorine levels above 5, you can dilute one part pool water with one part distilled water, mix well, draw your test sample from that, run your test, then multiply your result x 2--you lose a little accuracy in the dilution, but it'll work for what you're doing.

Good luck, and I also hope it stops raining soon!!

Janet

Janet,

Thank you for your very courteous reply. I did neglect to add my CC reading, which in the case of my pool is zero. I have not had a discernible CC reading since I've opened the pool this spring.

I was simply concerned about the heavy bather load from my recent party. The "algae" I spoke of may or may not be algae. It just seems in some areas, mainly hard to brush places like step crevices, there was some very slight light brown to yellowish discolorations. Not really spots, but more like smudges. I've been told this may not necessarily be algae, but could also be some sort of stain from the trees of foliage in the area.

I did end up pouring two gallons of bleach into the pool, which brought the FC up to about 7-8 ppm, and ran the filter a lot. The water is sparkling and I've noticed a slight difference in some of the smudge areas, which really weren't that noticeable in the first place.

I suppose I am just trying to stay ahead of the game. I'll keep reading and researching, in the meanwhile my pool is beautiful.


Mike
Arlington, TX

Quote:

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Originally Posted by Strawfoot

I was simply concerned about the heavy bather load from my recent party.

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Most of the folks on this forum will tell you that there's no need to shock unless you have a CC of .5 or greater. I personally tend to stay on the conservative side of things and shock my pool after I've had a big bather load, because in my own pool I have seen both beginnings of algae AND the aftereffects of large groups of kids in my pool (that have been in the water for extended periods of time with no bathroom breaks), and in both situations my CC was zero. It only costs a few bucks to shock it, and I personally would rather shock it too many times than not enough.

Just my $0.2, for what it's worth! :)

Janet

Mike,
You can also do a little prophylactic "near-shocking" before pool parties or other high chlorine demand events. In your pool, adding 1.5 -2.25 gallons of 6% bleach (2-3 3 quart jugs) will increase your free chlorine by 3.3 to 5 ppm which, in conjunction with your normal SWG production, will probably be enough to handle all the stuff that 15 or 20 bathers introduce and still leave you enough residual to keep the algae at bay until your SWG catches up the next day.

Also, most SWG manufacturers recommend 60-80 ppm CYA. I'd bring it into that range unless yours recommends something different.

Lastly, if your brown patches are leaf stains, shocking the pool will usually get rid of them. I get those in my negative edge trough from oak leaves and acorns and a jug or two of bleach in there for a couple of days erases the stains.