Why do we need water softeners?
Rainwater which falls on chalk and limestone dissolves and collects hardness minerals such as calcium and manganese. This water collects in underground aquifers before either naturally coming back to the surface as streams or being pumped via a borehole. The minerals naturally drop out of solution forming scale deposits, especially when the water is heated. In many applications this scale build up becomes unsightly or interferes with the efficiency of applications, and needs to be removed. Just 1.6mm of scale build up will cause a 12% loss in heating efficiency in boiler water. Softened water also reduces the excessive use of detergents and soaps.
The most common method of removing hardness (scale) is with an ion exchange resin. Water softeners are specific ion exchangers that are designed to remove ions, which are positively charged. Softeners mainly remove calcium (Ca2+) and magnesium (Mg2+) ions. Calcium and magnesium are often referred to as ‘hardness minerals’
How does it work?
An automatic water softener consists of a pressure vessel filled with resin. Located on the top of the pressure vessel is the control valve. The water is passed through the control valve and down through the vessel. As the water passes across the resin bed, the calcium and magnesium attach to the resin so the water leaving the unit is soft.
Periodically, depending on how much water is used, the resin needs to be refreshed. This is done by flushing a small amount of salt (stored in an external brine tank) though the resin vessel. Once this process has been completed the resin is refreshed and ready to begin again.
How to size
Properly sizing a water softener is all about matching your specific water quality and water use to a sufficiently sized system that will minimize salt use and maximize soft water capacity. Likely items to consider are size of demand, flow rate required, location, type of installation, available backwash water required.
A water quality test report should be obtained to ensure the appropriate equipment is suggested.