United Chemical Pool Stain Treat, 2 lb, PST-C12

Pool Stain Treat from United Chemical, part PST-C12, is a 2 lb stain treatment that does two jobs: it lifts staining that is already on the surface, and then keeps stains from returning for up to 60 days.

Dosing and application

One bottle treats 20,000 gallons. On colored plaster, painted surfaces, or where staining is widespread, predissolve it in a bucket of water and broadcast it evenly across the surface so it does not streak. On other surfaces, add it directly to the water in the area of the stain. Always add it to the pool or spa itself, and follow the product label, since using it in a way inconsistent with that label is a violation of federal law.

Getting the best result

Let the chlorine residual drop to 1.0 ppm or less before treating, and repeat the treatment every 60 days to keep staining from recurring. Two habits work against you: continuous shocking, which can bring staining back, and high alkalinity, which does the same. Balancing the water is part of the fix, not a separate job.