What causes the stains in pools plaster?
There are many reasons your plaster gets stained. Leaves,tree debris and other organic materials have pigments that can stain plaster. High amounts of metals in your fill water causes stains. Old pool equipment made of brass, iron, copper, steel, etc. causes metals to get into the pool. Most new pool equipment is made of fiberglass or high tempered plastic to reduce metal breakdown. Fertilizers from your yard have iron in them as well, which often is blown into the pool. Some large rust stains in plaster can be rebar or the tie wire of the rebar in the gunite shell itself bleeding through to the surface of the pool.
