Liquid Chlorine (Bleach) concentration or lack thereof...

I need some advise as I think my local pool store is trying to swindle me. My 10,000 gallon in ground salt water vinyl pool started to turn slightly green (I could still see the bottom).

I added 1 gallon of liquid chlorine that states it's 10.5% concentration. The water initially turned darker green but the color began to lighten the next day. I had the pool store test the water and they measured 4ppm of chlorine and stated I needed to shock again. So this time, I purchase 2.5 gallons of the same liquid chlorine and add it too the water.

After 5 hours, I see no change in the water color, which is unusual as in the past it would have already turned a light grey color. So I had them test my water again and the total chlorine and free chlorine both still indicate 4ppm!

They tell me it's not unusual because there is algae in my pool which immediately consumes the chlorine and I need to keep purchasing and adding more until I kill it??

I believe they are full it but need someone more experienced to confirm. Here are the specifics listed on the last water test performed 5 hours after adding 2.5 gallons of shock:

TC - 4ppm
FC - 4ppm
CC - 0ppm
pH - 7.5
Total Alk - 125ppm
Calcium Hard - 100ppm
Stabilizer - 60ppm
TDS - 4000ppm
Salt - 2,900ppm

I hate to tell you but I don't think they are scamming you. When you have an algae bloom you need to shock and test your water two or three times a day, not just once. FC levels can drop that fast.
We always recommend you test yourself with a FAS-DPD chlorine test. I cannot remember off the top of my head if a CYA/stabilizer level of 20 or 25 is required (about 2.5 gallons of the LC you are using)

You also want the store to test for copper...

An "easy" way to check and adjust more than once a day for working folks is this. Test and adjust when you get home from work, before bed, and when you get up in the morning. You would be well served to have more than one of those jugs on hand while shocking. Personally, I'd have three - assuming they're the 2.5 gallon jugs common in FL. When you're done cleaning up the mess, most stores will give you some kind of refund for the returned extra jugs.

Most pool stores don't sell the K-2006 (the big Florida based pool store chains do not), and you don't want the K-2005 which they do sell. http://poolforum.com/pf2/showthread.php?14994 This link tells you about test kits. You can get a cheapie "HTH" kit from walmart while you wait for a good test kit to come in from amazon (or some other place). The page I linked talks about the HTH kits and also provides links to the better kits.

I have the K-2006 FAS-DPD test kit... I simply expected the chlorine levels to measure higher than 4ppm after adding 3 1/2 gallons of 10.5% LC to a 10,000 pool with such a light bloom but according to Carl, I may have been mistaken. I did test for copper and none was detected. I did some more reading and found a way to test the LC's concentration by diluting it so I'll give that a try. Thanks for your help.

Bleach concentrations *should* be up to par, this time of year, when it's not so hot. In summer? Not so much.

But, as you've been told, algae can 'consume' bleach almost instantly, till it's dead and fully oxidized.

If you want to compare, buy Walmart bleach (8.25%) and see what sort of result you get. I'm pretty sure their bleach will be close to spec, though I have not tested it.

Once you get this bloom cleared up, make sure you keep your chlorine up so it won't happen again. Chlorine levels are based on your CYA readings. You can read more about this in the Best Guess Chlorine Chart in Ben's signature above.

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