Re: Texas Plaster Pool Metal Stains
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!
18'x36' free-form 17.4K gal AG pool; Skimmer Tabs & Hand Granular; Hayward DE3620 DE filter; Century B854 1 1/2 HP pump; 24hrs; AquaChek 7 Test Strips; utility water; iPhone; PF:7
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