Water quality is a significant concern for many households, influencing everything from the taste of drinking water to the longevity of appliances. Terms like “hard water” and “soft water” frequently appear in discussions about water supply, describing distinct characteristics that impact daily life. Evaluating water treatment methods requires understanding these distinctions.
Understanding Water Hardness and Softness
Water hardness refers to the concentration of dissolved minerals, primarily calcium and magnesium ions. As water travels through the ground, it picks up these minerals, with higher content leading to harder water. Soft water, conversely, contains low concentrations of these specific minerals.
Hard water indicators often include soap scum, a sticky residue left when soap reacts with calcium and magnesium, making it difficult for soaps to lather. Mineral buildup, or limescale, also appears on faucets, showerheads, and inside appliances like kettles, dishwashers, and water heaters, reducing their efficiency and lifespan. In contrast, soft water allows soaps to suds easily and prevents mineral deposits, resulting in cleaner dishes, softer laundry, and smoother skin and hair.
How Reverse Osmosis Works
Reverse osmosis (RO) is a water purification process that effectively removes a wide range of dissolved solids and impurities from water. This method utilizes pressure to force water through a semi-permeable membrane, which acts as a highly selective filter. The membrane’s pores are exceptionally small, allowing water molecules to pass through while blocking larger contaminants.
External pressure forces water from a concentrated solution through the membrane to a less concentrated side, overcoming osmotic pressure. This process filters out dissolved salts, heavy metals, suspended solids, and other impurities. Rejected contaminants are then flushed away, leaving purified water.
The Softness of Reverse Osmosis Water
Reverse osmosis water is soft water. The RO membrane effectively removes the dissolved minerals that cause water hardness, specifically calcium and magnesium ions, because these ions are larger than water molecules and cannot pass through the membrane’s tiny pores. RO systems achieve a significant reduction in total dissolved solids (TDS), removing approximately 95% to 99% of dissolved salts and other contaminants. This results in mineral concentrations often as low as 1-5 mg/L (ppm), ensuring the water produced is notably soft.
Characteristics and Considerations of RO Water
RO water’s softness offers several practical household benefits. With scale-forming minerals largely removed, RO water prevents limescale buildup in appliances, extending their lifespan and maintaining efficiency. It also enhances soap and detergent effectiveness, leading to better lathering, reduced product usage, and cleaner results for laundry, dishes, and personal care. For some, impurity removal also improves drinking water taste.
However, RO systems’ extensive filtration largely removes beneficial minerals like calcium and magnesium. While the human body primarily obtains essential minerals from food, not drinking water, some prefer to reintroduce them. Additionally, RO water often has a slightly acidic pH (5.0-7.0) due to the absence of buffering minerals that stabilize pH. Remineralization filters can be integrated into RO systems to add back beneficial minerals like calcium and magnesium, improving taste and raising the water’s pH closer to neutral or slightly alkaline levels.