When metals are present in pool water, they will need to be removed as soon as possible so that they don’t stain your pool. You should regularly add a metal sequestering product (stain and scale preventer) before you have any issues. If you are unsure of what to add, be sure to have your pool tested for metals by a pool professional at least once a month. If you test your pool water and see that the water shows a metal level of .2ppm or above, it is advisable that you add a stain/scale preventer weekly or bi-weekly. A good rule of thumb is to alternate your weekly shocking with weekly stain/scale preventer.
A metal sequestering product will grab the metal where it will be filtered out by your pool’s filter – keeping it from staining your pool walls. You should run the filter continuously for 24 hours after adding it to remove as much as possible. This will also prevent scale formation on pool surfaces and equipment.
Staining and scaling of pools is most noticeable in white plaster pools but it is best to identify the source and type of staining to know how to treat it. A copper metal stain will appear aqua or blue while iron stains will appear a rust or black color. The presence of manganese will appear black. Scale will appear as splotchy gray or brown and is rough to the touch.
What Causes Black Stains?
The metals present in water are caused by the metals in your water supply, from erosion and corrosion of metal fixtures/fittings and even fertilizer. If stains appear, be sure to adjust the pH and alkalinity to recommended ranges. You should then vigorously brush the stained areas. Add the metal out treatment and run the filter. Two days later, you should shock your water. You should then retest your pH and alkalinity. If your metals are still present repeat the process.
Identifying and treating metal stains can be challenging. It is recommended that you consult your pool professional prior to any treatment process.