Preventing Winter Pool Stains

stained-pool-surfaces - note the blue-green copper stainingIf you’re concerned about pool stains, know this – winter pool stains occur more easily than summer pool stains.

The reason is simple, without circulating, filtering and balancing your pool water – stains find it easier to attach to pool surfaces.

Metals (like Iron and Copper), Minerals (like Calcium or Salt) or Organic debris from leaves and pollutants, can all stain swimming pool surfaces.

How to Prevent Winter Pool Stains

Balance Winter Pool Chemistry

One of the most important things to prevent winter pool stains from minerals, metals or dirt – is to keep your water balanced. Especially for mesh pool covers, which allow rain and snow melt to pass through to the pool, bringing with it air borne contaminants, pollutants, pollen and dust.testing-pool-water-during-winter

Checking your pool water chemistry during winter is not something most people would do, but if you want to protect against stains – test your water every month, and make adjustments as needed for pH, alkalinity and calcium hardness levels.

Keep the Pool Covered Tightly

Any debris that gets into the pool will consume sanitizer, affect your water balance, and potentially stain the pool. Inground pool covers that fit loosely, allowing debris to blow under or around the pool cover are sure to develop some localized or generalized (all over) staining.

For safety covers that but up against a raised wall, pool noodles or inflated water bags can be used to seal up against the wall. For safety covers on a pool with flat (not bullnose) coping, use water bags around the edge to seal up the edges.

Use Stain & Scale Preventative


We need to prevent both – Stains and Scale. Use stain prevention chemicals during winter to keep minerals locked in solution. These chemicals are known as ‘sequestering agents’, and they bind to minerals and metals, to keep them from coming out of solution and staining.

Stains occur from metals dissolved in the water, from dirt and oils that get in the pool, or from dirty scale deposits.

Scale occurs when minerals like calcium or sodium salts come out of solution and deposit themselves on pool surfaces. Before they deposit, they often combine with suspended dirt or contaminants, creating scale that is different color than the pool surface – a stain.

pool-floaterIf you use a Winter Kit, containing a non-chlorine winter floater – rest easy. Don’t Use chlorine tablets in a winter floater however – that’s a bad idea. If the floater stays in one spot for too long, or if it tips over and spills it’s contents – a stain.

Tips for Salt Pools

Don’t add salt to your pool without being able to run the pump for circulation. If you add salt during winter, or if the salt comes out of solution, you may get – a stain.

Salt pools should always use a Stain & Scale chemical to prevent salts from coming out of solution. Natural Chemistry makes a line of sequestering agents made for salt pools, such as Salt Water Magic, Cell Protect, Scale Free, Metal Free.

eclipse3-ejectorjacks-magic-purpleSalt pools with very high calcium hardness, or TDS (total dissolve solids) may have to be more vigilant to avoid scaling stains. Jack’s Purple Stuff, and Eclipe3’s Ejector are two products that you should be using.

Tips for Vinyl Liner Pools

Harsh chemicals like shock and pH down, or acidic based stain removal chemicals can damage a vinyl pool liner. Keep your pool clean and add pre-dissolved pool chemicals carefully, one at a time, in the deepest part of the pool, and you can avoid – a stain.

blog-winter-ball of enzymesVinyl liners can be more stain resistant than gunite pools. Minerals and metals have a hard time attaching to the slick surface. However, bacteria, dirt, oil and other organic gunk can stain. Enzymes like the Winter Ball, can help by consuming oily gunk.

Tips for Plaster Pools

Avoid using too much copper based algaecide, unless you really like the color teal! Another source of copper is a gas pool heater. Very low pH in the pool can strip the heat exchanger copper pipes.

Calcium and Sodium salts can find an easy home on your surfaces, being attracted by the salts in a plaster surface, and depositing as dirty scale. Keep your calcium hardness levels correct, and if you use a salt system, be sure to keep the salt ‘sequestered‘ during winter and avoid – a stain!stains-stink!

Fight your stains all year long – even during the off season! Only 2-4 more months of winter – depending where you live! 🙂

Jackie Wolski
InTheSwim Staff Blogger


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