Rust stains on the bottom or greenish-tinted walls aren’t just an aesthetic problem: they’re a sign that something isn’t working properly in the chemical balance or the metal components of your pool. The sooner you identify the cause, the easier (and cheaper) it is to fix.<\/p>\n\n
In this guide we review the three most common issues related to pool water in Mallorca: rust stains, algae and general chemical imbalance.<\/p>\n\n
In Mallorca, it’s common to fill swimming pools with well water, which typically has a higher iron and manganese content than mains water. When this water comes into contact with chlorine, these metals oxidize and deposit as brown or reddish stains on the bottom and walls.<\/p>\n\n
Other common causes:<\/strong><\/p><\/p>\n\n How to treat it:<\/strong> A treatment with a metal sequestrant prevents iron and manganese from precipitating as a stain. If the stain has already formed, a specific rust inhibitor applied locally will usually remove it without needing to drain the pool.<\/p><\/p>\n\n Not all algae are treated the same, and applying the wrong product only delays the solution.<\/p>\n\n Green algae:<\/strong> the most common type, giving the water a uniform green hue. They usually appear due to a lack of chlorine or insufficient filtration.<\/p><\/li>\n\n\n\n Black algae:<\/strong> These adhere to the walls as dark spots and are very resistant to standard chlorine. They require mechanical brushing in addition to specific chemical treatment.<\/p><\/li>\n\n\n\n Mustard algae (yellow):<\/strong> less frequent, they accumulate in shaded areas and are resistant to normal chlorine levels.<\/p><\/li>\n<\/ul>\n\n General treatment:<\/strong> first adjust the pH (ideally between 7.2 and 7.6), apply a shock treatment with chlorine and, in the case of black or mustard algae, supplement with a specific algaecide and manual brushing of the affected areas.<\/p><\/p>\n\n Good water quality depends on more than just chlorine levels. Key parameters include:<\/p>\n\n pH:<\/strong> between 7.2 and 7.6. Outside this range, chlorine loses effectiveness and increases the risk of irritation or corrosion.<\/p><\/li>\n\n\n\n Total alkalinity:<\/strong> acts as a pH stabilizer; if it is unbalanced, the pH fluctuates constantly no matter how much it is adjusted.<\/p><\/li>\n\n\n\n Calcium hardness:<\/strong> water that is too hard promotes limescale buildup; water that is too soft causes corrosion of metals and linings.<\/p><\/li>\n\n\n\n Chlorine or salt level (depending on the system):<\/strong> should be kept constant, not just corrected when there is already a visible problem.<\/p><\/li>\n<\/ul>\n\n Most of these problems don’t appear overnight\u2014they’re the result of weeks without checking the water’s chemical balance. Regular monitoring (weekly during peak season) detects deviations before they develop into staining, algae, or cloudy water.<\/p>\n\n Do rust stains damage pool liners?<\/strong> Can I take a bath while treating algae?<\/strong> How often should I check the pH of the water?<\/strong> Does well water always cause rust problems?<\/strong> Does your pool have rust stains, algae, or is the water not maintaining good condition despite regular treatment? At JM Cifre Piscinas, we diagnose and solve water quality problems in Mallorca.<\/p>\n\n\n
Algae: Identify the type before treating them<\/h3>\n\n
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Water quality: the parameters that need to be monitored<\/h3>\n\n
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Prevention: the key is regularity<\/h3>\n\n
Frequently Asked Questions<\/h3>\n\n