What Causes Stains on Commercial Pool Membranes?

Organic Staining

Organic stains can range widely in color and intensity.

The most common sources of organic stains are:

• Dirt
• Mud
• Leaves
• Algae/Bacteria
• Bugs
• Other organic debris

Green or brown membrane stains usually come from organic matter like algae, leaves, bugs, and mud. Red or purple stains often come from berries or fruit falling into the pool from nearby bushes or overhead trees. Light pink stains can also be a sign of bacterial buildup. Black stains/spots on a pool membrane can come from algae buildup.

Metal Staining

Metal stains come in a wide range of colors and are typically caused by:

• Metal pool parts (ladders)
• Corroded pool pipes
• Pool heaters
• Water

Teal or blue-green stains indicate that you have an issue with copper. The copper stains could be originating from pipes or they could be leaching from the pool heater due to improper chemical maintenance. Reddish-brown stains typically come from iron in the pool. Sometimes, the pool membrane will also be stained yellow. These rusty patches on the membrane can come from metal parts, like handrails or ladders, but they can also be caused by corroded iron pipes or well water. Grey to black stains on a pool membrane also often come from metals like manganese which usually comes from well water.

Note: Most pool stains are also either caused or worsened by inadequate water chemistry conditions.

Tips to Reduce the Risk of Pool Membrane Stains

• Keep your pool chemistry balanced
• Keep debris out of the pool, and don’t let leaves or dirt sit on steps or the pool floor
• Use metal sequesters when needed to keep metals from building up again if you’ve had problems with it in the past
• Using a pool cover to keep dirt and debris out
• Brush and vacuum your pool as required to avoid accumulation of contaminants

Please consider that the above circumstances are unlikely to occur if proper care and maintenance of the swimming pool are observed.