Some homeowners actively try to soften their water using a number of different systems. The sodium enters the drinking water instead, which can also affect taste in large quantities. Sometimes this system is used only for hot water heaters so extra sodium is not drunk, but expensive pipes and equipment are protected. Another softening method is a lime-soda process, involving the reaction of lime and soda ash reacting with hard water producing a insoluble precipitate with calcium and magnesium ions. These ions no longer interfere with cleaning soaps, but the precipitate can still leave films and be drunk.
Humans can increase the amount of hardness in waterways in a few ways.
Some industrial discharges can be high in calcium and metals. Wastewater from homes is often high in cations from household cleaning agents, food residue, human waste, and from rinsing out the trapped calcium and magnesium from an ion exchange filter system when changing the salt. All of these cations cannot always be removed by water treatment facilities before discharging to a stream. Government agencies do hope that a level of hardness does exist so that pipes are less corrosive, limiting the release of metals that do need to be regulated.