Hardwater not only leaves streaky deposits of calcium and rust on all surfaces, tastes bad, but it also lowers the effectiveness
of cleaning products dramatically.
Typically most products estimate usage with hard water when printing dilution instructions. With hardwater it typically
takes 35% more product to a worse job! Below I’ve written a brief primer on how hardwater effects cleaning chemicals
and how products use “chelating” agents to reduce the impact of hardwater somewhat.
A surfactant is the most important part cleaning chemistry. The word surfactant is short for “Surface Active Agent.” They are chemicals that, when dissolved in water or another solvent, orient themselves at the boundary between the liquid and a solid (the dirt), and modify the properties of the interface.
When dirt or grease is present the surfactants surround it until it is removed from the boundary – suspending it which allows it to be removed/cleaned.
Soil removal is quite a process that is more involved than adding soap or surfactant to water. One of the concerns in dealing with cleaning compounds is water hardness. Water is made “hard” by calcium, magnesium, iron and manganese metal ions. These metal ions interfere with the cleaning ability of detergents. The metal ions act like dirt and “tie up” the surfactants, making them unable to act on the surface we want to clean. A chelating agent combines itself with these disruptive metal ions in the water. The metal ions are surrounded by the claw-like chelating agent which alters the electronic charge of the metal ions from positive to negative (see diagram below.) This makes it impossible for the metal ions to be precipitated with the surfactants. As a result, chelated metal ions remain tied up in solution in a harmless state where they will not use up the surfactants.
So do chelating agents allow soap/detergent (surfactants) to clean just as well with hard water vs distilled or reverse osmosis? No. They help but the bottom line is that you lose about 35-50% cleaning effectiveness when using hard water. That’s why our maid service uses distilled water – which – in the end – actually costs less since we consume about 40% less of our cleaning products.