There are generally three different types of water softener salts available:
Some retailers sell technologies meant to prevent scale build–up in household appliances without the use of salt, and sometimes even water. Most of these alternative technologies do not soften water (i.e. do not remove calcium and magnesium) but instead change the properties of suspended solids in the water to stop scale from forming on water heater elements, taps, etc. In some cases the technologies still require backwashing. Examples of these water softener alternatives are:
There is currently very little information published by independent agencies to verify the effectiveness of these new technologies. A recent study published by the U.S. Water Reuse Research Foundation clarifies the effectiveness of the four technologies listed above.
Some retailers sell alternatives to traditional water softeners that prevent scale buildup without the use of salt, and sometimes even without water. Most of these alternative technologies don’t soften water—i.e. they don’t remove calcium and magnesium. Instead, these alternatives change the properties of suspended solids—small, solid particles suspended in water like calcium and magnesium—to stop scale from forming on water heater elements, taps and showerheads, clothes and dish washers, and other water using appliances. Examples of these alternatives include:
A recent study published by the U.S. Water Reuse Research Foundation (WRF) (link to study) clarifies the effectiveness of the four alternatives listed above.
The WRF study concluded that all four alternatives prevented scale buildup on water heater elements with varied results. NAC/TAC reduced scale buildup on water heater elements by over 90 per cent, matching the effectiveness of salt-based water softeners. The NAC/TAC units needed no salt or water to operate.
The NAC/TAC units use polymeric beads with nucleation sites to convert dissolved hardness into microscopic crystals. These crystals are then released by the beads (or “media”) and remain as insoluble particles that will not form scale on surfaces. No salt, water, or energy is required. Figure 1 below illustrates the crystallization process.
Figure 1 – Nucleation Assisted Crystallization / Template Assisted Crystallization
The 2015 purchase prices for NAC/TAC units tested by the Region of Waterloo and City of Guelph were comparable to purchase prices for equivalent ion exchange (salt-based) water softeners (estimated range $999–$1,499). The estimated price to replace exhausted NAC/TAC media every four years ranges from $250 to $875, which is $62 to $218 on an annual basis. This compares favourably with the estimated annual operating costs of ion exchange water softening of $125 to $248 per year per household for salt, water and energy (Region of Waterloo Residential Water Softener Performance Study Testing Report, October 5, 2012).
With similar costs, the advantage to NAC/TAC units comes largely in reduced care and maintenance as the media only needs to be replaced about every four years. There are also environmental benefits from using less water, salt and energy, and health benefits for those without hard water taps for drinking.
During 2014and 2015, the Region of Waterloo and City of Guelph completed a market study and performance test of NAC/TAC. Here are some quick findings from the partnership:
For more details read the NAC/TAC study report by Dr. Peter Fox.