Our pool has had significant stains in the spillover spa since we purchased the home and accompanying pool 2 years ago. I paid very little attention to he spa, since we almost never use it. I assumed that it was mineral staining, but none of the stain testing made any change so I let it be. By the way, the spa is surrounded by piñon pine trees that drop copious needles in the spa.
This year the stains bothered me, so I did the testing again. Still no change. However, this time just to see I left a puck on a stain for an hour or two. When I came back it had cleared out a nice circle, the clean circle being about 2 inches larger than the puck. So my answer is organic stains, but very stubborn stains.
The standard treatment for stains is to hold a puck or vitamin c on the stains. Problem is my stains take 1-2 hours to remove. Much of the spa is covered, including sidewalls, so the time involved would be significant.
Is there a way to make the spa acidic enough to take away the stains? I have a booster pump that only runs the spa and bypasses the heater, so I could keep the spa water away from filter and heater while it does it’s thing.

This year the stains bothered me, so I did the testing again. Still no change. However, this time just to see I left a puck on a stain for an hour or two. When I came back it had cleared out a nice circle, the clean circle being about 2 inches larger than the puck. So my answer is organic stains, but very stubborn stains.
The standard treatment for stains is to hold a puck or vitamin c on the stains. Problem is my stains take 1-2 hours to remove. Much of the spa is covered, including sidewalls, so the time involved would be significant.
Is there a way to make the spa acidic enough to take away the stains? I have a booster pump that only runs the spa and bypasses the heater, so I could keep the spa water away from filter and heater while it does it’s thing.
