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hey guys,

i have a 20,000 gallon pool with a 72gph flow rate hayward de filter. i haven't really run the filter all winter so my pool is really green. I cleaned all the leaves off the bottom and have sucked all the crap off the bottom. I used shock packs with 70%free chlorine about 4 at a time and it just barely made a difference in the color of the water. My filter keeps clogging up with it running, DE is getting expensive and it's getting really bothersome to have to keep backwashing and adding de every 30mins. I just bought 16- 128oz dollar general 6% bleach bottles and emptied them all in my pool. The ph was 7.5-7.8 before adding the bleach. Did i add too much at once or is that a pretty good initial dose of chlorine to get the algae under control? and what's my next step?

Thanks a bunch,


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Hi Michael,

Yeah, that was a lot of bleach. According to the Pool Calculator you raised the FC by at least 39 ppm. That'll kill those green buggers, eh?

Do you have a test kit? If not, the Taylor K-2006 is excellent, well worth the money, and refills come in a variety of quantities which makes the K-2006 economical in the long run. Another good kit is TF-TestKits which has a slightly lower start-up cost but refills are smaller.

A good test kit in combination with the Pool Calculator will take the guess work out of chemical additions and subsequent balancing of the water. Both of these kits test for CYA (stabilizer), a value which is critical to the correct FC level for your system. Spend a little time playing with the Pool Calculator, it's pretty self-explanatory.

As to your DE filter, it's my understanding DE filters don't get backwashed. Instead, you take out the cartridge and clean it or replace it. You might pick up a package of skimmer socks, they'll help hugely in catching dead algae and other debris before it gets into the filter medium. You put a skimmer sock inside the skimmer basket, folding it over the outside where it's held by the elastic on top of the 'sock'. Change that frequently and rise it out, they're good to reuse several times.

Keep your pump running, brush the bottom frequently, clean the DE cartridge as needed. I know, it's a pain in the behind and it'll take a few days to get the water cleaned up. The FC will drop fairly quickly depending on how much algae was in there to start with and you may actually have to continue shocking, but how much additional bleach you'll need will depend on the CYA. If you have a pool store nearby you could take a sample in and have them check for that. Of course, they'll tell you the sky is falling and will want to sell you a number of expensive potions and powders. Try to resist. In the end, all you'll really need is bleach, baking soda or 20 Mule Team borax, maybe some muriatic acid, maybe stabilizer.

If you do have the water tested, or if you have a test kit, please post your numbers.


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