Commercial hotel pool, 23,000 gallons, 22 years old. I'm assistant manager of the property.
It's been about 10 weeks since we re-plastered our pool. No start-up help provided by the contractor other than "brush it twice daily for 2 weeks" - nothing about chemicals or special treatments. After 6 weeks, we noticed blotchy dark stains all over the floor of the pool. Talked to the contractor, he said if we drain it he would come up and acid wash it, blamed us for not using a metal sequestering agent and said it was probably iron and manganese and copper. We drained it, his guy acid washed it, ground down a few spots here and there, and then (on a day I wasn't personally here) reportedly used a torch to "bring the stains up" before acid washing one area.
That area is still darker than the surrounding, never really looked like the stain had come up properly. We started using a metal sequestering agent about 12 hours after starting the re-fill.
After reading on this site for the last few days, I understand that acid washing lowers the life expectancy of the plaster. After having our local pool store test the water, they found no metals but a higher level of total hardness than our calcium hardness test + tap water hardness (they measured that too for us) can account for.
Testing today (Taylor test kit):
pH 7.6 (added 8oz Aqua Guard pH Down to bring down a little)
FC 8.0 (shocked it last night due to an oil slick showing up on the surface, letting it drop down naturally in the sun)
CC .5 or less
TA 100
CH 160
CYA < 30
Please understand that I have to keep it within limits set by Washington State Department of Health and I can't close it for any measurable length of time....
But what do I do?
It's been about 10 weeks since we re-plastered our pool. No start-up help provided by the contractor other than "brush it twice daily for 2 weeks" - nothing about chemicals or special treatments. After 6 weeks, we noticed blotchy dark stains all over the floor of the pool. Talked to the contractor, he said if we drain it he would come up and acid wash it, blamed us for not using a metal sequestering agent and said it was probably iron and manganese and copper. We drained it, his guy acid washed it, ground down a few spots here and there, and then (on a day I wasn't personally here) reportedly used a torch to "bring the stains up" before acid washing one area.
That area is still darker than the surrounding, never really looked like the stain had come up properly. We started using a metal sequestering agent about 12 hours after starting the re-fill.
After reading on this site for the last few days, I understand that acid washing lowers the life expectancy of the plaster. After having our local pool store test the water, they found no metals but a higher level of total hardness than our calcium hardness test + tap water hardness (they measured that too for us) can account for.
Testing today (Taylor test kit):
pH 7.6 (added 8oz Aqua Guard pH Down to bring down a little)
FC 8.0 (shocked it last night due to an oil slick showing up on the surface, letting it drop down naturally in the sun)
CC .5 or less
TA 100
CH 160
CYA < 30
Please understand that I have to keep it within limits set by Washington State Department of Health and I can't close it for any measurable length of time....
But what do I do?
