Green Fog in Pool - new user/never posted anywhere....

[chem geek]

The polymeric clarifier would have been caught in the filter and then removed by backwashing (since it sounds like you've got a sand filter). That would have also removed most negatively charged particulate matter including some algae. Chlorine would have fully oxidized ammonia, urea, and some other nitrogenous compounds into nitrogen gas and carbon dioxide that will have mostly outgassed. Some other organic compounds will get partially oxidized and remain dissolved in the water. Some others are volatile and would outgas. Many won't react with chlorine and will either remain dissolved (including salts) or will be insoluble so will either form scum at the surface or will have been handled by the clarifier.

The thing to remember is that though algae is unsightly, it is not itself a health hazard (unless there is so much that you can't see the deep end or that it is on surfaces and is slippery). The result of clearing the water doesn't result in toxic compounds remaining. The vast majority are innocuous and in small quantities. There are some disinfection by-products from chlorine oxidation, but the amounts are relatively small and in an outdoor residential pool exposed to UV from sunlight it tends to be minimal.

As for the Green to Clean and Yellow Out, these are sodium bromide products so have essentially turned your pool into a bromine pool. Over time, bromine will slowly outgas from the pool and some brominated organics may get caught in the filter and backwashed, but given how much you've added to the pool that could take quite some time (i.e. years). So when you add chlorine to the pool, it is getting used up converting bromide to bromine -- hence, you've really got a bromine pool right now. 14 pounds of sodium bromide (assuming these products are pure sodium bromide) in 26,000 gallons (40' x 16' x 5.5' average depth) is 64 ppm bromide so not a small amount. That's the worst part of the advice that you were given from the pool store. Now bromine is a sanitizer like chlorine, but it is not protected from breakdown in sunlight so you may find that your chlorine usage goes up on sunny days compared to before. Bromine also smells a bit different than chlorine (actually, I'm referring to bromamine smelling different than chloramines since that's what you smell when bromine or chlorine react with the ammonia from your sweat from your skin).

So your pool is safe, but is no longer a chlorine pool -- it's a bromine pool.

[leonard]

Wife and kids want to go swimming in the pool.

Test results are as follows:

h = 250
tot chl = 1
free chl = o
pH = 8.4
alk = 240
cyn = 150

Is it safe to swim? Or what can I do immediately to modify values to allow swimming.... Please let me know as the kids are chomping at the bit as the pool looks ok

[chem geek]

Your pH is too high so you need to add acid to lower it. Your FC is too low so you need to add chlorine to raise it. You can use The Pool Calculator to figure out dosages though pH adjustment amounts are approximate so you'll add and retest. Your chlorine went away very quickly so you may still be killing off algae, but if you don't stay on top of the chlorine level then algae can come back. Shocking is not a one-time process.

[leonard]

My kids were in the pool over the past few days and the algie has come back and it is turning slightly cloudy....

The test kit arrived and the results are below. Chlorine floater 3" tab dispenser was down to two tabs.... I have since filled.

If you could give me some advise on the next step I would appreciate it. I am adding 5 gallons of 6% bleach at this time..

Thanks,
Len

"0" Free Chlorine
0.4 Chl
7.6-7.8 pH
150 Tot Alk.
370 Calc Hardness
75 = Cyn

[leonard]

After putting in the bleach last night, the pool is now very green and very cloudy. Any suggestions?

[CarlD]

I think you need to get your Free Chlorine level up to 20ppm and keep it there, given a CYA (Cyanuric Acid) level of 75ppm.
I would not use floaters, any kind of chlorine tablets or chlorine powder at all. Your CYA is high and your Calcium, while in the safe range, is toward the high end. Your best bet is bleach or liquid chlorine. I'm guessing your pool is 35,000 to 40,000 gallons (40'*16'*8'= 5120 cubic feet. 7.48 gal/cubic foot = 38297.6 gallons). You'll need 12 or 13 gallons of 6% bleach to get there, or about 6 gallons of 12.5% liquid chlorine. Then you have to keep it at that level, testing and adding 2 to 3 times a day until it's clear.

But if you don't do it your pool won't clear.

(if you figure 40,000 gallons, it takes 4 gallons of 6% to raise your FC by 6ppm)

Carld

[aylad]

Follow Carl's advice and get your chlorine up to shock level (20 ppm for CYA that high) and hold it there until it clears up, as he said. However, once you get it cleared up and clean again, with your CYA that high, you need to not let your chlorine EVER get below 5 ppm, and I would keep it up closer to 7, just to give yourself some wiggle room. If you let it go below the 5 ppm, you're inviting the algae in....

I would also stop using the pucks in the floater--they are continuing to raise your CYA level, and you're going to have to keep upping your chlorine levels to compensate, if you want your pool to stay clear......

Janet