Opening pool, it's nasty green

[Brian87gt]

My wife and I moved into a new home, needless to say the prior owners didn't close the pool down at the end of last year. The water is green, and i'm sure there are leaves on the bottom. It's an AG 10,000 gallons. I went to get the water tested today. The person told to me to brush, and to get all the leaves out that I can. Then add 2 gallons of shock at night, then two more in the morning. The only thing I don't understand is she said to wait until the water is clear to add the stabilizer. Wont the chlorine be wasted without any CYA. Here are the test results:

Saturation - 0.6
CYA - 0
Total CL - 0.1
Free CL - 0.0
PH - 8.3
total alk - 51
total hardness - 337

It has a sand filter.Thanks

[chem geek]

The pH also needs to be lowered. As for the chlorine, it won't get lost at night from sunlight so the CYA doesn't matter overnight, but you are right that during the day the chlorine will get broken down from sunlight so at least some will be wasted from that. I suspect the thought is that you may have ammonia as well as algae in the pool and that it will consume the chlorine faster than the sunlight will break it down. However, I think that SOME CYA would be good, even if it wasn't a lot -- 10-20 ppm even. Of course, that will slow down chlorine's effectiveness, but shocking to 10-15 ppm FC should still be fine even with some CYA in the water.

If you had CYA in the pool before the winter when it was "let go", then soil bacteria could have converted the CYA into ammonia in which case it will take a LOT of chlorine to get rid of it. You can get an inexpensive ammonia test kit from a fish/pet/aquarium store. It will take an FC amount around 10 times the measured ammonia amount to get rid of and then it will take more chlorine than that to get rid of the algae. Hang in there, it can be done using chlorinating liquid or unscented bleach alone as you can see from this thread.

Richard

[Guest]

So you are saying she was correct then? Go ahead and shock it, and keep the CL level high until the pool clears, and then add the stabilizer? Thanks

[chem geek]

I'm saying it depends, but personally I'd add at least a little CYA to the water. It's not a disaster if you just follow what she says (so far), though do lower the pH (she didn't mention anything about that and it's currently too high).

[Guest]

Would you lower the PH first? What is the best way?hanks

[chem geek]

Well, I'm not sure I trust the pool store numbers and you should get your own good test kit -- either the Taylor K-2006 test kit at a good online price here or the TF100 test kit from tftestkits(dot)com here with the latter having 36% more volume of reagents so comparably priced "per test".

Assuming the measured numbers you gave are correct, then your pH is high and your TA is low (which is an unusual combination). To get the pH to 7.5 and the TA to 80, it will take 2 cups of Muriatic Acid (31.45% Hydrochloric Acid) and 8 cups of Arm & Hammer Baking Soda (same as Alkalinity Up from the pool store -- both are Sodium Bicarbonate). You first add the acid and do so slowly over a return flow with the pump running and then after you've added it lightly brush the side and bottom of the pool where you poured so you thoroughly mix the water. For the baking soda, you can either pour this over a return or distribute it around the pool -- it dissolves quickly and is safe so it doesn't matter how you distribute it.

HOWEVER, if you want to raise the CYA level then you can use Dichlor as your source of chlorine for shocking adding around 6 cups which will raise the FC and CYA each around 20 ppm. If you do this, then you do not need to add the acid as the usage of this chlorine will be acidic (the pH is neutral when adding it, but as the chlorine gets used up the pH will drop). You'd still add the 8 cups of Baking Soda either way (whether adding acid or adding Dichlor).

Richard

[Guest]

Can I add the stuff to raise the PH, and the CYA at the same time? Thanks