What is Water Softening Resin?
Water softening resin is the media that is inside your water softener that allows the softener to remove hard water minerals from your water. Water softening resin is a small porous beads that are formed from two materials. These materials are polystyrene and divinylbenzene. During the manufacturing process beads are formed out of polystyrene and then cross linked with divinylbenzene to hold the bead together. Softening resin is usually white or yellow, but some black varieties also exist.
How Does Water Softening Resin Work?
Water softening resin works through a process called ion exchange. In a water softener, ion exchange replaces positively charged calcium and magnesium ions in the water with positively charged sodium ions that are attached to the surface of the resin bead. The resin continues to perform this process until all the sodium ions have been depleted from the surface of the bead. At this point regeneration is required to flush away the calcium and magnesium ions and replace the sodium ions on the resin. Regeneration is performed by using a high concentration of aqueous (water based) sodium chloride or potassium chloride.
Does the Quality of Softening Resin Matter?
Water softening resin comes in various grades. The grades of softening resin are determined by the quantity of cross-linking that occurs in the bead. The quantity of cross-linking ranges between 2-20%. The higher the cross link, the stronger and more resilient the bead, but result in poor efficiency, lower capacity, and higher regenerations costs. The cross link of water softening resin is dependent on how much divinylbenzene was used during the manufacturing process. The most common grades of water softening resin used in professional water treatment equipment is 8% and 10% cross-linked. 8% cross-linked resin has the benefit of increased efficiency, higher capacity, and lower regeneration costs when compared to 10% resin. However, 8% cross-linked resin will break down much more quickly than 10% cross-linked resin, eventually leading to decreased performance and the eventual failure of the unit. The calculation for determining the life expectancy of water softening resin is (% Cross-link/ppm of chlorine) = years of service life. If we used this calculation in a simple example comparing the life expectancy of 8% vs 10% cross-linked resin, we can begin to see the advantages of higher cross-linking. Let’s say your incoming water has a chlorine content of 1 ppm. In the scenario 8% resin would last:
% Cross-Link (8)/ppm of chlorine (1) = 8 years of service life
Whereas 10% cross-link would last:
% Cross-Link (10)/ppm of chlorine (1) = 10 years of service life
While this may not seem like a massive increase in life, it is in fact a huge improvement. The cost difference between 8% and 10% cross-linked resin is very small, as is the cost of any extra water and sodium chloride required by the 10% resin. However, if you had a water softener installed for $1,800, the cost per year can be as high as $225. In which case, the extra two years of life achieved by the 10% resin could save you $550. It is also important to note that this example only takes into account the damage caused to resin by chlorine. Additional damage is caused by the hydraulic and osmotic shock that is encountered during day to day operation and regeneration. The extra strength provided by 10% over 8% resin provides much greater protection to this mechanical/chemical wear. Manufacturers claim that overall 10% cross-linked resin should have up to twice the life of your typical 8% resin due to its more durable structure when you take into account all of the factors that can affect resin life.
As you get into higher cross-linked resin above 10%, the disadvantages of decreased performance and cost typically outweigh the benefits of longer life. Resins between 12-20% cross-linked are typically reserved for extreme situations typically encountered in commercial or industrial applications, and would rarely be seen in a home.
What Causes Water Softening Resin to Fail?
Regardless of the grade of water softening resin you choose; the resin will eventually fail. There are many factors that can cause failure in water softener resin. These include:
- Chlorine and Chloramines – Breaks down the cross-linking of the resin bead causing resin swelling, decreased capacity and weakening of the bead.
- Temperature – Breaks down the cross-linking of the resin bead causing resin swelling, decreased capacity and weakening of the bead.
- Hydraulic Shock – Because a water softener is located at the beginning of your homes plumbing, it takes the brunt of the abuse from water hammering. Over time, old and worn resin beads are destroyed by this process. This destroyed resin breaks down and gets washed out the drain. The decrease in resin available results in severely reduced capacity.
- Osmotic Shock – Over years the process of regeneration and the periodic swelling and contracting of the water softening resin gradually causing the resin to break down. This results in severely reduced capacity.
- Iron and manganese Fouling – Water softening resin will remove iron and manganese from water like it removes calcium and magnesium. Unfortunately, during the regeneration process, the iron and manganese is not removed from the resin bead. Over time the iron and manganese build up on the resin, resulting in severely decreased capacity.
How Can I Extend the Life of My Water Softening Resin?
There are many things that will degrade the performance of your water softening resin over time. Fortunately, there are some steps that you can take to improve the performance and increase the life span of your system. These steps include:
- Chlorine and chloramines can be removed from your water by installing an activated carbon filter before your water softener.
- Hydraulic shock can sometimes be reduced by installing a pressure regulator if incoming water pressure is unnecessarily high.
- Issues created by iron and manganese fouling can be greatly improved by adding a resin bed cleaner, such as Pure Kleen, to the brine well of your brine tank each time you add salt.
Taking these steps can help ensure you will get full system life and performance out of your water softener. If you have any questions about how your water softener works, or how you can take care of your system, please do not hesitate to contact us.