Algae caused by chlorine???????

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dndntsd

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Dec 1, 2013
19
OK, here is a weird one for you guys.... hope you can help me. I have a new pool - 35,000 gal, rough concrete waiting for tile to arrive. We're using the pool until the tile gets here. The chemistry is still out of whack, i.e the PH is 8.0, not enough CYA yet etc. But here is the weird thing...

I'm using powdered Trichlor, adding until my FC is about 7PPM at night, the sun cooks it off during the day until it is about 1-2PPM in the late afternoon then I repeat the process. I have very little to no CC and the water is crystal clear. BUT... it looks like spots of green algae are growing on the floor but I deduced that it only happens where I put the chlorine. I mix the Trichlor in a bucket of water then pour it into the pool. There is a bit of residual powder that doesn't get dissolved and it sits on the bottom - the next day, right where the powder was is a patch of what looks like green algae. It doesn't keep growing and it doesn't go away. Has anyone encountered this before? any help would be greatly appreciated.

Thanks
 
Do you have your own *good* test kit yet? For a big pool like yours I would suggest the TF-100 <link in my siggy line>. You need it STAT!

How about a full set of test results and we can see what's in need of tweaking. What has been put in the pool up to this point? How much CYA have you added? New plaster often causes pH to rise, and you need to control your chemistry so that your plaster cures properly.

In the meantime, why not use liquid chlorine (aka "bleach") to chlorinate and see if that works better for you? I don't believe letting undisolved chemicals lay on your new plaster is a good idea and may cause problems you'll regret.
 
I'm thinking the "algae" is staining/bleaching form the chlorine sitting on the bottom.

How long have you been add the TriChlor like this?

A full set of test results including CYA would help.
 
Leaving trichlor on the floor of your pool is going to bleach or stain it, period. Happened to me a couple times in my pre-TFP days when I would just chuck the floater in and the lid would pop off.

If I were to take a shot in the dark I would say you have copper in your water and the low pH and high FC in that area is causing it to stain your pool. But, again, total shot in the dark.

From my HTC One via Tapatalk
 
Thanks for the replies. I'm using the Taylor K-2006 kit. Here are all the test results:
FC - 3.2
CC - 0
PH - 8.0
CH - 1100 (yes 1,100 ppm)
CYA -less than 20
TA -250

So, the pool is new, the concrete has had Fester additive to make it impermeable. I've only had water in it for 2 weeks and I was hoping to get the PH down by adding Trichlor and having the CYA do the job. I think that may take longer than I thought.

The "staining" sure looks organic to me, kind of slimy to touch and dark green in color. I wondered about copper but I don't know what it looks like.
 

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OK, this definitely brushes off. The trichlor is by Astral Pools. The label says "Trichloroisocyanuric acid powder".
It is 90% available chlorine. I had a look at the MSDS sheet on it but it only deals with the 97% powder, not the other 3%. I'm in Mexico so maybe the other 3% is Tequila?
 
Doubtful. :mrgreen:

So you have Algae then. It's a matter of FC getting too low, and with 3.2 showing, I imagine you've had windows for growth more often than you think. You've got more going on with the pH and Calcium, but if you are draining to install tile soon you might be ok. Still, it might be better to not have a scaled surface prior to install.
 
Strange though that the only place the algae grows is where the powdered chlorine sits on the bottom....

Hopefully a good scrub with the pressure washer will clean the surface enough for the tiles. I don't see any scale. Do you think I will need to do something else like wash with acid or something?
 
dndntsd said:
Strange though that the only place the algae grows is where the powdered chlorine sits on the bottom....

Hopefully a good scrub with the pressure washer will clean the surface enough for the tiles. I don't see any scale. Do you think I will need to do something else like wash with acid or something?
Click to expand...
Trichlor is very acidic. It may have started etching the surface where it always settles in the same spot. Algae clings and grows better on rough surfaces than on smooth surfaces. For instance, you're more likely to see it growing on grout than right next to it on the smooth glazed tile. Even the mildew in the shower does the same.
 
Thanks for all the help everyone. I think this may be one of the great mysteries of life. I've changed how I add the Trichlor; I take more time to dilute it and make sure there is no powder residue on the pool bottom. So far the algae has not returned. Problem solved I guess.
 
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