What are the visible signs that water quality in a Mallorca cistern has deteriorated?

Visible signs that water quality in a Mallorca cistern has deteriorated can often be observed through changes in the water’s appearance, smell, and sometimes taste. One of the most noticeable indicators is a change in the water’s clarity. Clear water can become cloudy or murky, suggesting the presence of suspended particles, algae, or microbial growth. If the water develops an unusual color such as greenish, brown, or even reddish hues, this is a strong sign of contamination, often due to algae blooms or rust from corroded pipes or the cistern itself. Sediments settling at the bottom or floating debris may also indicate poor maintenance or infiltration of external pollutants.

Another visible sign is the formation of biofilm or slimy residues on the walls or surfaces within the cistern. This slimy layer is usually a sign of bacterial activity and can contribute to unpleasant tastes and odors in the water. Additionally, stagnant water in a poorly ventilated cistern might produce a musty or earthy smell, which signals microbial overgrowth or organic material decay. In some cases, the water may develop an oily sheen or small scums on the surface, which could result from contamination by oils, detergents, or other pollutants entering the cistern.

Careful observation of these signs is important, especially since the cisterns in Mallorca traditionally collect rainwater and are susceptible to environmental factors such as bird droppings, leaf litter, and soil erosion. If any of these symptoms are present, it is advisable to avoid using the water for drinking or cooking until it has been tested and properly treated. Regular cleaning, covering the cistern to prevent contamination, and ensuring proper filtration are essential measures to maintain water quality. Recognizing these visible warning signs early can help preserve not only the water's safety but also the long-standing tradition of sustainable water storage in Mallorca.