Stains on vinyl pool liners

Organic stains typically come from dirt and dead algae that die and leave marks behind, often called non-living organic stains. They commonly form in corners and areas with low water circulation. Also, tannins from leaves and vegetation often create a brown tint across the entire pool surface. These stains slowly develop over time and generally resist scrubbing or chlorine treatments.

Copper stains show as a teal (blue/green) color and often darken or become more prominent after shock chlorination, as chlorine oxidizes the copper. The image at the top of the page showcases a severe case of copper staining that we effectively removed. In contrast, iron stains typically exhibit a brownish hue and, although brushing may temporarily remove them, they frequently resettle and re-stain the pool.

Low alkalinity or calcium hardness can damage the pool’s vinyl surface. When water is unbalanced, it tries to stabilize itself by slowly breaking down the vinyl, which leads to staining that’s hard to repair. In addition, extended exposure to high chlorine levels can permanently damage or bleach the liner. Although pool liners are durable, they aren’t built to handle excessive chlorine for long periods.

Most often, stains on vinyl pool liners are typically caused by copper, algae, calcium, or minerals.  However, stains from fungus or bacteria are rare but do occur. These stains develop when dye-producing microorganisms accumulate beneath the vinyl, leading to discoloration. Over time, this staining becomes visible on the pool’s surface, often appearing as gray marks on the sides or bottom of the pool that do not respond to brushing, chlorine, or stain removers.  

Some sources suggest that shock chlorination and copper-based algaecides can eliminate these stains. However, based on our experience with clients, this method is often ineffective or only provides temporary results. This is because the staining originates beneath the liner rather than on its surface. We are actively researching this issue further.

If you are considering replacing your liner due to this problem, treating the sand base of the pool with microbial protection before installation is a smart choice. There are several treatment options available, so consulting with your vinyl supplier can help determine the best solution for your specific situation.  Treating the sand will help prevent this from occurring again.  Also using quality vinyl is most important.

Keep in mind that mineral and copper stains are stubborn and won’t simply brush away. For effective stain removal, our specialized treatment process is your best option.

You can read more about this issue on our blog.