Hoping to get rid of stains (stain test)

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alexvilper

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Jul 15, 2014
52
Boca Raton, FL
Hi guys,

Since it's "cold" here in South Florida, and we're not using the pool, I wanted to try to get rid of the stains in my pool. I moved into this house in 2014, and the pool has had stains since before, and I don't think they are getting worse, which to me seems to be a good thing.

IMG_20160208_071909.jpg


I have been reading about Ascorbic Acid treatment and others, and today I decided to do a little test, (all using a dry sock with a rock inside) and here are the results:

Ascorbic acid (about 7 min): Stain turned darker (brown)
Dry acid (10 min): Cleared the stain
Chlorine puck (5 min): Nothing (or stained a little more, not sure, results are not clear)

Based on those results, what would be the best course of action, known that the most of the stains are on the deep end?

My latest pool chem full test results, from yesterday are:

FC: 9
CC: 0
PH: 7.9
TA: 80
CH: 250 (added 20oz Calcium Chloride - trying to raise it a little bit since it's the min end based on PoolMath)
CYA: 40

It's very windy today, and pictures are not really coming out good, I will take some once winds settle.

Thanks!!!
 
Last edited:
Hi Dave,

I added a picture from this morning, but since it's on the deep end, the stain is not very visible on the pic. I will try again this afternoon, with the sun shining on it.

Since the stains are on the deep, I actually never thought about going through them with my hands, it we will have to wait until the water is warm again :)

The stains are like yellow-orange-brownish, it's the best I can describe. For context, CH was very high at one point, over 500, and so was CYA, I did partial drains and refills until I got CYA down to 30's. I never really paid much attention to CH until now. Because everything is falling into place, after all these months.

I picked up the test for Dry Acid from this post I read yesterday - see comment from JasonLion (09-29-2011, 01:52 PM)

Thanks!
 
I scanned the "dry Acid test" thread just a bit but couldn't find the reference. It doesn't matter I was just curious.

So, everything here tells me you have calcium scale. Here's some options....

1. Lower pH down to 6.8 and keep it there. Make sure you can test to 6.6 but, in any case, hold that pH down at 6.8 and monitor it carefully. The Calcium will start to disappear (it's still there, it'll just be in soluble form) Once scale is removed to your satisfaction, use a sequestrant and hold your pH so it doesn't go much higher than 7.4.....that'll keep the CH in solution.

2. Drain the pool and do an acid wash on the plaster.....typically not a DIY job

3. Read up on this website on how to give your pool a no-drain acid bath. Google that name and you'll get plenty of info.
 
Hi Dave,

I have a K2006 test kit which does not go below 7.0 for PH, and one of those cheap 2-way tests which goes to 6.8. Is the latter good enough, or should I buy a different test kit? I wanted to try your option 1 first, since it seems to "easiest" approach, comparing to the other two. Also, is there a kind of specific sequestrant for calcium? Is something like this OK? BioGuard Scale Inhibitor

Thanks much!

- - - Updated - - -

Thanks @pooldv!
 
I would suggest you spend the money and get a pH scale that's trustworthy. You are lowering your pH down pretty low and you want something dependable to test it

Part # 9781 is the Taylor pH test that we use in the TF-100.....it goes down to 6.8 and is pretty accurate.

I think TFTestkits.net stocks it but call them to see. Probably available many places on the net, too.

I have no opinion or experience with the actual application of sequestrants.
 
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