Pool turned green after using StainFree

[moyer02]

Thanks to the BBB and this terrific website, my pool has been troublefree for years. I couldn't find a recent post about why my pool is green after using StainFree, thus this post:

I noticed some small brown stains on my vinyl liner this year, caused by leaves left in the pool too long. So, I purchased some StainFree. I dropped my chlorine to zero and PH to 7.0, and on Day 1, I added the StainFree and within minutes the stain was gone. (I added some Super Blue overnight).

On Day 2 (the next day) I then vacuumed to waste and backwashed my sand filter. (But forgot to rinse).

On Day 3 I again vacuumed to waste, backwashed again and rinsed. Added about 6" of water to replace what was lost.

On Day 3 I added 24 oz of bleach to get my Chlorine up to 1. The pool turned green nearly right away. I've been running my pump 24/7 for two days since and there's been some improvement (paler shade of green. I can now see the drains).

Day 5 numbers: PH 6.8; TC 0; TA 60; CH 240; CYA 20 (or less, the black dot didn't disappear competely after using the entire sample.) Salt 2800.

I'm inclined to leave things as is and keep the pump running 24/7 for another day or two and see if the water turns clear again. I'm afraid to add any more bleach or other chemicals at this point.

I used StainFree once before and after adding bleach, my pool turned green, but the next day, after running the pump all night, it was clear the following day. Not sure why it's taking longer this time.

Any help or suggestions would be most appreciated.

 

[pooldv]

Sounds like you've got some iron in the water. What are the ingredients of stainfree? Are they listed?

Go ahead and add a sock/knee high of CYA to raise to 30 ppm. You will want cya at 50 for the summer anyway. And I would add 3 ppm of FC daily.

More on iron here, Pool School - Pool Stains

 

[moyer02]

Thanks. The StainFree is 100% citric acid. The instructions say to very gradually increase the FC afterwards. I'm thinking I didn't wait long enough to add the bleach. Also, never had a problem with iron before (the pool is 9 years old). I'll go ahead and add the CYA as you recommended.

 

[pooldv]

Ok, citric acid or ascorbic acid will lift iron from the pool surface and put it into the water. Which is why the water turned green. Then a sequestrant is used to bind to the iron to keep it in suspension so the water isn't green and it doesn't stain the pool surface. You can also try some polyfill pillow stuffing or paper towels in the skimmers to grab the iron while it is in the water.

Small amounts of iron in your fill water will slowly build up over time until it starts staining or turning the water clear green. A partial water change might dilute the iron enough to eliminate the problems.

 

[JoyfulNoise]

If you have a choice next time of using either citric acid or ascorbic acid, you'd be better off choosing ascorbic acid. Citric acid is over 3 times more acidic than ascorbic acid on a molar basis and chlorine reacts with citric acid to form, in part, chloroform which is a very unhealthy trihalomethane (THM) to have in pool water. It will dissipate with time but it's not good. Ascorbic acid, on the other hand, does not form any dangerous THMs when it reacts with chlorine. Also, it takes 3 times as much chlorine to neutralize citric acid than it does ascorbic acid.

Also, brown leaf stains are generally not metallic in nature, they are caused by tannins. Tannin stains are definitely hard to remove but it is usually sufficient to just raise the FC level for an extended period of time to lighten them OR spot treat them with a chlorine tablet or sock full of dichlor powder.

 

[moyer02]

Thanks again. Is there a particular brand/type of sequestrant you would recommend. Is that the same thing as a clarifier? I'm confused with all the different types of Jack's Magic Sequestrants: purple, blue, sapphire, etc. Appreciate your help.

 

[pooldv]

ProTeam's Metal Magic or Jack's Pink Stuff is good for your pool. No, a sequestrant is not the same as a clarifier.

 

[moyer02]

If you have a choice next time of using either citric acid or ascorbic acid, you'd be better off choosing ascorbic acid. Citric acid is over 3 times more acidic than ascorbic acid on a molar basis and chlorine reacts with citric acid to form, in part, chloroform which is a very unhealthy trihalomethane (THM) to have in pool water. It will dissipate with time but it's not good. Ascorbic acid, on the other hand, does not form any dangerous THMs when it reacts with chlorine. Also, it takes 3 times as much chlorine to neutralize citric acid than it does ascorbic acid.

Also, brown leaf stains are generally not metallic in nature, they are caused by tannins. Tannin stains are definitely hard to remove but it is usually sufficient to just raise the FC level for an extended period of time to lighten them OR spot treat them with a chlorine tablet or sock full of dichlor powder.

JoyfulNoise: Thank you for this info. Will definitely use ascorbic acid next time!