SLAMmed pool, passes test, but still have some questionable spots on pool's surface

May 11, 2010
25
East Texas
Good morning,

I have a new (built Oct 2015) pool at my new house which is on lakefront property. Until a week ago, the water and chemicals have been in good shape. I brush the pool almost every day because we don't have grass growing around the pool yet so it stays very sandy/dirty from the windy conditions and the deluge of rain we've had recently in East Texas. Over the weekend, I noticed some stains on the pool -- mostly from midway to the deep end. They look greenish and some are dark to me from above and from within the pool (looking through goggles). I couldn't get down to scrape any of it, but it didn't feel any different than the rest of the pool's surface when I ran my foot across one of the stains. Prior to my noticing this, about 3 weeks ago we had grass seed hydromulched, and a few days before I noticed the spots, we had a torrential 5 inches of rain and lots of dirt, grass seed, and who knows what else washed into the pool.

On Sunday, I checked all of my levels (FC = 4, CC = 0, PH: 7.4, CYA=70, TA=80, CH=300) and started SLAMing the pool. Finally, this morning, I had lost only 1ppm chlorine. The CC has been 0 this entire time. The pool did look cloudy earlier in the week, but has cleared up and looked pretty sparkly yesterday. However, the stains are still there. I've brushed at least twice a day every day this week. Should I keep SLAMing or move on to something else to determine what these spots/stains are? What else should I be doing/looking for/testing for? I left a message with my pool builder to see if he could come out and give his opinion.

Thank you for your help!
 
Time for a trichlor and Vitamin C tablet test. Place a trichlor tablet on the stain for a couple minutes. If the stain fades, it's an organic stain. If it does not, hold some Vitamin C tablets inside a sock on the stain for several minutes. If it fades, then it's a metals stain.
 
You should be able to buy a single packaged trichlor tablet (7 - 8 oz) at most places that stock pool chemicals. Wouldn't buy a bucket or anything. If you leave the trichlor in place too long, it can bleach/fade your pool surface so only for a couple minutes to see if you can observe fading of the stain.
 
Metals stains it is. Vitamin C tabs worked. Upon closer inspection in the pool, the walls are streaked with these metal stains/deposits. I was able to write HI in the wall with the vitamin c tablet. My questions:

Is my next step a complete asorbic acid treatment?
If so, is this okay with a diamond brite quartz plaster--should I contact my pool builder to do it to preserve any warranties?
What do I do to determine where this is coming from and prevent it in the future (I've read a little about sequestrants)? This pool was built and filled in October so this was a pretty quick acculturation I think.

Thanks for your help!
 
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