Inorganic Stains

Salt Stains

Appearance

• Brownish in colour, located where salt is left to sit.

Causes

• Salt stains result when salt is added to the water but the surface is not brushed sufficiently to prevent the salt from settling on the surface.

Rust Spot/Marks (See also Calcium Scale)

Appearance

• Reddish-brown stain on the surface

Possible causes

• Rust stains occur when metal settles on the surface and corrodes. If the stain appears to be coming from something in the surface then some metallic particles may have contaminated the render as it was being applied.
• Metal stains commonly occur from hair clips or pieces of jewellery that are left to sit on the surface etc.
• Small rust spots on the surface may be the result of work conducted near the pool whereby particles of metal have found their way into the pool.
• A high content of Total Dissolved Solids (TDS) can cause metal staining.
• Corroding reinforcing steel causing metal stain through to the surface.

Removal

• In most of these instances (rust and salt stains), sprinkling citric acid onto the mark should remove it. If the staining is on a vertical surface, the citric acid can be placed in a stocking and allowed to sit on the mark.
• If there are too many marks for localised treatment, lower the pH down to 6.8, reduce the chlorine level down to between 0.5 and 1 ppm and sprinkle citric acid on the water’s surface, concentrating on contaminated areas. Allow the pool to sit for 12 – 24 hours. 2 – 4 kg per 50,000 litres of pool water is an acceptable dosage rate depending on the severity of the marks.