When water evaporates, it leaves all the dissolved solids behind. This is a common problem with hard water in water heaters. The solids build up on heating elements and diminish the efficacy of the heat-transfer process. The dissolved solids can also build up inside pipes when they precipitate and choke down the fluid flow. This, in turn, makes the pump work harder to overcome an increased resistance to flow.
An adequate remedy for small systems is to install a water softener to reduce the solids content in the circulating fluid. This device precipitates solids in an inert chemical process before the water flows into the hot-water tank.
An important issue to consider, in any hot-water heater or small boiler project, is that these instruments have an inherent inefficiency. For example, to create 100 units of hot water the heater or boiler must spend 120 units of energy. Conversely, when an energy-conserving project is projected to save 100 units of energy by thermal balance calculations, it actually saves 120 units when evaluated as a system. In this sense, the system inefficiency is a savings amplifier.
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Excerpt from Energy Conservation Projects.
