Texas Plaster Pool Metal Stains

[Captain Ron]

Thanks for your reply. One comment disturbs me...the unsucessful results!

QUOTE..."BUT . . . don't follow that process just yet. I've had a couple of unsuccessful results, and I need to work out a way to prevent that. I can tell you one change to the procedure will be "Get a K2006 and report your pH, TA, and CH" BEFORE you start!" We may need people to get a TH (total hardness test) as well."...QUOTE

I have a 14 year old pool with a new 1 year old plaster finish. I've fought this problem for a few years and feel the treatments I've tried in the past contributed to the failure of the plaster.

The rest of the thread makes sense as I've experienced it all! It appears this has been a "solution' for some time as evidenced by the time/date tags. Why the misgivings now?

[PoolDoc]

We're getting more consistent feed back, from people following the process as written. That makes it possible to more accurately evaluate how well it's working.

One of the big problems all of us have, is that WE don't have most of the problems users come here with -- we learned to avoid them, long ago. So, we have to rely on user feedback for more information. But pool owners are so used to failure with pool products and processes that they don't always tell us when something we've recommended doesn't work as we expect.

I'm hoping the new Pool Chart + the Pool Log (customized dosing calculator and test record for subscribers) will allow us to improve our advice a LOT, over the next year. It's probably already the best available, but it's a long way from perfect.

[Captain Ron]

Can you please clarify!

Your post seems to be at odds with another moderator/administrator! The post I refer to is "Ascorbic treatment for stains" (original by mbar, posted by aylad, and updated by PoolDoc in 2012)

[PoolDoc]

Yeah, I"m at odds with me.

I'd rather you NOT start the AA treatment till you have a K2006 and have reported accurate pH, TA, and CH measurements.

[Captain Ron]

Thanks! Now i understand. Kit is on order but I also have the HTH 6 in 1 from Walmart!

I'm not quite ready anyway as most of the chemical tools haven't arrived.

[PoolDoc]

Lemme know when you've got everything.

[Captain Ron]

These may or may not be metal stains! Don't let me lead you astray!

Results of K-2006 tests:
FC - 2.4
CC - 0
pH - 7.4
TA - 110
CH - 430
CA - 135 (1:1 distilled water method)
One week ago I discontinued using dichlor granules and trichlor tablets. I now use liquid bleach.

History:
14 year old 17,400 gallon gunite pool/spa, DE filter (no heater bypass), with an 18 month old new plaster finish. I had this type staining before the new finish. I had mixed success with some products lightening or eliminating the stains before the new finish...always a metal stain remover product, but they returned over time. About 4-5 months after the new finish, staining creeped back in the pool over a 6 month period. On startup of the new finish, I was aggressive on adding an HEDP product (Metal Hold from Ram Chemicals, Houston, TX) which I believe is as good but cheaper than Jack's Magic and KemTek. I base this on conversation with the manufacturer and the recommended dosage; I was unable to determine the %HEDP.

My pool contractor led me to believe I had a problem called calcium carbonate hydration. I researched the problem and found others with the exact symptoms. I used a treatment method I obtained from a Jack's Magic rep (she said I had scale over metal staining) where you lower the chlorine to zero then add acid to drive th pH to below 7 (5 gallons for my pool) and 2 quarts of Metal Hold. The stains started disappearing after 48 hours and were mostly gone after 96 hours (pool eqipment OFF!). I brought the pH back to 7.4, restarted the filter, backwashed after 2 days, and gradually brought chlorine back to 3. This was in March 2012 when water temp was 70 degrees so algae was not a problem. I have been aggressive in adding Metal Hold weekly and when adding water from the city supply. I think I may have slowed the stain progression but am unsure. The stains started creeping back 3 months later as the water temp reached the 80's.I DO NOT want to repeat this treatment again as I feel it slightly diminished the quality of the plaster.

Observations:
The stains appear blotchy beige/brown. They started appearing in the shallow end (3 foot) at the curvature of the wall and floor and have progressed to the deep end (6 foot). Some staining also has occurred on the floor and to a lesser extent on the walls. A couple of months back I tried a brush on them with no effect. I then got very concientious on using Metal Hold at twice the mantenance dosage.

Today I donned a mask and weight belt to further investigate and experiment. I found I could use a stainless steel brush (very aggressively) and remove some of the top of the stain but no more. I used a teaspoon of ascorbic powder in a nylon stocking weighted over a stain which removed some of the stain (over time) but a shadowey outline remained. I used a squirt bottle with muriatic acid on a stain, wiped it immediately, and it floated off, again with a shadowey outline remaining. I rubbed a trichlor tablet on a stain then scrubbed with no effect.

The stains do not feel rough to the bare hand in some areas but slightly so in others. In some areas of the floor I feel tiny sharp pin prick protrusions that are not visibly noticeable. Looking around the pool underwater with a mask, I think I perceive widespread tiny pin points of staining that is not noticeable from above the surface.

Well, thats it! Suggestions please!