Stain ID

[jimwill]

Hi everyone! Anyone recognize this stain? This photo is from my top step. The white areas on each side of the tiles are what the plaster used to look like. It's visible in the bottom of the pool too.

It's not organic. I haven't tried a Vitamin C test yet. Could it be calcium scale?

 

[Texas Splash]

It looks like scale discoloration to me. How old is the pool/plaster? Are you the original owner?

 

[jimwill]

I'm not the original owner. No idea how old the plaster is. We've been in the house for six years, and this discoloration started within the last six months.

 

[Texas Splash]

this discoloration started within the last six months.

That's interesting. Do you have any pool testing history by chance? Something to help give us more clues? What products have you been using this season for chlorination?

 

[jimwill]

Sadly, I was using chlorine pucks with stabilizer and a weekly shock using Cal Hypo powder. The pool shock would leave powder at the bottom that I would have to vacuum out, but sometimes it would sit at the bottom for a week or two.

Over time, the CYA level became very high. That's when I found this site and decided to get serious. I did partial drains and refills, and now the CYA is at 40. And I began using liquid chlorine, but this was just within the last few weeks.

 

[Texas Splash]

It's possible the cal-hypo resulted in some scaling and/or perhaps even encased some organic staining within it. It happens. Hard to tell in the pic above, but is the pool empty?

 

[jimwill]

No, the pool is not empty. You guys helped me get my water so clear!

 

[JoyfulNoise]

Test with Vitamin C first before doing anything else.

 

[JamesW]

Probably iron and some scale.

Do you have a full set of chemistry readings?

What is the CSI?

What were the readings when you first tested the water?

 

[jimwill]

I tested with ascorbic acid today, and it's definitely iron. Here's a new photo of the same area:



No idea what the dark blue specs are, but they aren't very noticeable. There is some scale buildup here too.

We're using city water. Any ideas where iron came from? We did get a record freeze here in February that temporarily affected the water supply.

Should my next step be an Ascorbic Acid treatment? AA Treatment

Thanks!
Jiim

 

[jimwill]

What were the readings when you first tested the water?

I have not maintained the pool correctly since we bought this house six years ago, so I don't have any historical readings. I finally got serious, did some research, and found this site.

After using pucks with stabilizer for so many years, it became difficult to keep enough chlorine in the pool to prevent algae. My CYA was extremely high, so I spent a few weeks doing partial drains and refills to bring it down (nice water bill). Next, I worked on bringing down my TA which was 140.

Here are my current numbers:

FC: 3 (added LC to bring up to 5)
CC: 0
PH: 7 (low because I've been lowering TA with MA)
TA: 70
CH: 300
CYA: 40
Temp: 85
CSI: -0.66 (should improve as PH increases)

Thanks,
Jim

 

[Texas Splash]

I tested with ascorbic acid today, and it's definitely iron.

That's definitely easier to work with than scale. The link below might come in handy. If you can deal with the staining for a few more months, you might wait until Dec/Jan when our water temps fall below 60 to do the AA so that algae won't be such a concern when you drop the FC level down.

Pool Care Basics Archives

Your one-stop shop for all things TFP to include: ABCs of Water Chemistry, Recommended Chemicals/Levels, Test Kits, Troubleshooting, and much more!

www.troublefreepool.com

 

[jimwill]

I'll wait until the weather cools off for sure.

Ascorbic acid removes the stains, but the iron will stay in the water, correct? So the stains will come back if the PH gets too high?

I've read on this forum an alternative to ascorbic acid (Metal Magic) that works for some people and allows the iron to be filtered out. Does anyone have experience with this?

 

[calinb]

Yes--I did the ProTeam Metal Magic sponge test three years ago and I used the associated Metal Magic prescription. MM removed most of the stains (caused by spring water lab tested at 4.44 ppm Fe). The stains were more of a gray color than your stains. The pool water turned very white and I used polyfil pillow stuffing in my skimmer, ProTeam EXO clarifier in the water (crustacean chitin based) and ProTeam Dry Clarifier in my sand filter (a polymer sand filter enhancement but diatomaceous earth would probably work too). It took a few weeks but all the white eventually filtered out and the stains have not come back.

The next year I treated for copper stains caused by the previous owners use and abuse of Cu algaecide-laced chlorine pucks. I used the Jack's stain test kit to identify the origin of the stains as copper and did a sulfamic acid treatment that took from the 1st of September through most of December when I finally winterized the pool rather than run the pump all night. Once the water temp dips below 60, which it did in October, the stain removal action really slows down, but this process worked on the Cu stains that MM didn't touch (nor did my tests with ascorbic, citric or oxylinic acids or trichlor pucks touch these copper stains that Jack's identified and significantly mitigated).

I just calculated that I put close to 7500 gal. of replacement 4.44 ppm Fe spring water into our 17,500 gal pool every year for evaporation replacement and re-opening top-up. I know some mods here don't believe the Periodic Products chelating technology products work, but no water goes into our pool without going through a Periodic Products Fillfast filter (with plenty of filter dwell time at only 2 gpm max flow) and I run two Culator 4.0 eggs (a new one each season in the pump basket and last year's egg in the skimmer basket) along with a trace metal dose of HEDP sequestrant every month in-season to catch any trace metals. The eggs are noticeably brown when discarded after two seasons.

Our spring water is too limited to permit water dumps for dilution and water is too expensive to tanker here (only very small tanker trucks can be used on our grade) so, other than for closing, I never dump any water. The stains have not returned.