Hi folks! Hoping someone can shed some insight on my very odd situation. We had an inground pool installed last spring (2016) and had no issues with it all year last summer, chemical levels were always in check.
Issue #1
This year on opening it up and removing the winter safety cover I found a section of about 10" of the aluminum coping had "melted" for lack of a better term. Aside from having no chlorine levels on opening the water was clear with normal PH, etc. The coping continued to breakdown and the holes in that section became larger until the pool installer came out about 2 months after I had opened it to take a look. He said that he had never seen anything like it, and forwarded pictures and a sample of the goop coming out of the coping to the pool manufacturer (who also said they had no idea what was going on). The pool installer used a pressure washer to clean out the hole and we let it sit for a month to see if the problem continued to spread (it did not). After pressure washing there was a cavern in the concrete decking that ran the length of the damage and went back about 2"-3" under the concrete deck. The pressure washer did not create this hole in the concrete, so either whatever caused the coping to break down also ate the concrete or it was the substance itself that broke down the coping that also washed out with the pressure washer. My working theory is that there was a plug of lime power that didn't get properly mixed with the cement and it sat up against the coping. Over the winter the water level rose to the level of the coping, soaked into the lime powder and caused it to eat away at the aluminum. There are also stainless steel bolt heads that I can see in the cavern (the ones that attach the coping to the pool walls) that weren't affected by whatever ate away at the aluminum. The builder has since come back and filled the hole with an epoxy resin that is aluminum compatible and there hasn't been any further issue with that hole, although another tiny spot of coping (about 1/8" in diameter so far) has started to melt away on another section nearby. The pool manufacturer suggested that maybe it was a case of stray current that had broken down the metal, and they provided us with zinc anodes for the pool ladder and an in line zinc anode for the pool plumbing by the filter pad. Any theories on what did this?
Issue #2
A small amount of rust developed on the corners of the deep end ladder, near where the plastic step meets the stainless steel post. At the same time as coming out and pressure washing the coping hole out, the pool builder suggested I take the ladder out and clean off the rust with steel wool and CLR prior to installing the zinc anodes onto the ladder. I did this and it worked great, rust came off with no problem. I promptly washed it off with fresh water, then placed the ladder back in the pool. Within 2 days of this every part of the ladder underwater turned BLACK. It's like a soot residue that will partially come off on your hand if you rub it. I pulled the ladder and wiped it down with steel wool, no chemicals or CLR used, and it came off super easy. Put it back in the pool and, bam, 2 days later, same soot is back. Knowing that stainless steel gets it's "stainless" property by forming a barrier by reacting with oxygen I pulled the ladder, cleaned it off yet again with steel wool and let it sit out for a couple of days before putting it back in the pool. I also pulled the zinc anode off one side of the ladder to experiment if that was causing some sort of voltaic reaction and plating something onto the ladder. Two days later after going back into the water, soot is back, equally on the side with the zinc anode and the side without. So, thinking there is some sort free metal ion plating itself onto the steel I went to Walmart and bought 64 oz of HTH Metal & stain defense. Instructions say to pour into the pool near wherever the metallic stains are, so I poured it next to the ladder. By the next day everywhere underwater on the ladder that the solution seemed to touch the black was gone and it was shiny stainless again (eg, deep down at the bottom of the ladder it was still black). I thought my problems were solved! But now 2 weeks later we are back at square one with black soot covering every underwater exposed metal surface of the ladder. Any ideas? Everything was fine with this ladder aside from some tiny rust spots until I put CLR to it and the pool builder pressure washed the mysterious hole in the coping (both CLR and pressure washing happened the same day). Whatever was in that hole was also blown into the pool as he cleaned the hole out. Note that I don't have any other odd stains appearing in the pool on the liner or on the thermoplastic white stairs, it's only on the stainless steel ladder and the stainless steel ring around the underwater light (which hasn't been touched by steel wool or CLR since day 1).
I'm at a loss to these two issues, and the pool builder is pretty much just blowing me off now because they are out of ideas as to how to correct the issue.
Current Water Analysis (It has been steady around these values for 2 years now, checked biweekly)
PH 7.4
Free Chlorine 3 ppm
Alkalinity 100 ppm
Stabilizer 40 ppm
Salt level 2950 ppm
Pool specs
21,000 gallon inground liner pool (filled from city water)
Pentair Cartridge filter
Pentair Gas pool heater
Pentair VFD pump
Pentair Intelichlor IC40 SWG
Issue #1
This year on opening it up and removing the winter safety cover I found a section of about 10" of the aluminum coping had "melted" for lack of a better term. Aside from having no chlorine levels on opening the water was clear with normal PH, etc. The coping continued to breakdown and the holes in that section became larger until the pool installer came out about 2 months after I had opened it to take a look. He said that he had never seen anything like it, and forwarded pictures and a sample of the goop coming out of the coping to the pool manufacturer (who also said they had no idea what was going on). The pool installer used a pressure washer to clean out the hole and we let it sit for a month to see if the problem continued to spread (it did not). After pressure washing there was a cavern in the concrete decking that ran the length of the damage and went back about 2"-3" under the concrete deck. The pressure washer did not create this hole in the concrete, so either whatever caused the coping to break down also ate the concrete or it was the substance itself that broke down the coping that also washed out with the pressure washer. My working theory is that there was a plug of lime power that didn't get properly mixed with the cement and it sat up against the coping. Over the winter the water level rose to the level of the coping, soaked into the lime powder and caused it to eat away at the aluminum. There are also stainless steel bolt heads that I can see in the cavern (the ones that attach the coping to the pool walls) that weren't affected by whatever ate away at the aluminum. The builder has since come back and filled the hole with an epoxy resin that is aluminum compatible and there hasn't been any further issue with that hole, although another tiny spot of coping (about 1/8" in diameter so far) has started to melt away on another section nearby. The pool manufacturer suggested that maybe it was a case of stray current that had broken down the metal, and they provided us with zinc anodes for the pool ladder and an in line zinc anode for the pool plumbing by the filter pad. Any theories on what did this?
Issue #2
A small amount of rust developed on the corners of the deep end ladder, near where the plastic step meets the stainless steel post. At the same time as coming out and pressure washing the coping hole out, the pool builder suggested I take the ladder out and clean off the rust with steel wool and CLR prior to installing the zinc anodes onto the ladder. I did this and it worked great, rust came off with no problem. I promptly washed it off with fresh water, then placed the ladder back in the pool. Within 2 days of this every part of the ladder underwater turned BLACK. It's like a soot residue that will partially come off on your hand if you rub it. I pulled the ladder and wiped it down with steel wool, no chemicals or CLR used, and it came off super easy. Put it back in the pool and, bam, 2 days later, same soot is back. Knowing that stainless steel gets it's "stainless" property by forming a barrier by reacting with oxygen I pulled the ladder, cleaned it off yet again with steel wool and let it sit out for a couple of days before putting it back in the pool. I also pulled the zinc anode off one side of the ladder to experiment if that was causing some sort of voltaic reaction and plating something onto the ladder. Two days later after going back into the water, soot is back, equally on the side with the zinc anode and the side without. So, thinking there is some sort free metal ion plating itself onto the steel I went to Walmart and bought 64 oz of HTH Metal & stain defense. Instructions say to pour into the pool near wherever the metallic stains are, so I poured it next to the ladder. By the next day everywhere underwater on the ladder that the solution seemed to touch the black was gone and it was shiny stainless again (eg, deep down at the bottom of the ladder it was still black). I thought my problems were solved! But now 2 weeks later we are back at square one with black soot covering every underwater exposed metal surface of the ladder. Any ideas? Everything was fine with this ladder aside from some tiny rust spots until I put CLR to it and the pool builder pressure washed the mysterious hole in the coping (both CLR and pressure washing happened the same day). Whatever was in that hole was also blown into the pool as he cleaned the hole out. Note that I don't have any other odd stains appearing in the pool on the liner or on the thermoplastic white stairs, it's only on the stainless steel ladder and the stainless steel ring around the underwater light (which hasn't been touched by steel wool or CLR since day 1).
I'm at a loss to these two issues, and the pool builder is pretty much just blowing me off now because they are out of ideas as to how to correct the issue.
Current Water Analysis (It has been steady around these values for 2 years now, checked biweekly)
PH 7.4
Free Chlorine 3 ppm
Alkalinity 100 ppm
Stabilizer 40 ppm
Salt level 2950 ppm
Pool specs
21,000 gallon inground liner pool (filled from city water)
Pentair Cartridge filter
Pentair Gas pool heater
Pentair VFD pump
Pentair Intelichlor IC40 SWG
