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Water Softener Topic 11/11: Softener resin, what is it and how to choose?

Thank you for your overwhelming support to series of my posts relating to various aspects of water softener systems. I am penning this in response to some users requesting to understand importance of resin as it relates to water softener and how (if possible) to revive old softeners. I have received at least 3-4 requests in the past one week on this topic and thought, I would share what I know for the benefit of anyone owning a water softener or planning to have one.

Resin is an integral part of the water softening system. Given this, let us try to understand what are they? In simple terms they are spheres typically made of numerous Polystyrene (synthetic hydrocarbon polymer of styrene) strands and wrapped in a crisscross manner allowing water to passthrough the negatively charged (anion) carboxylate which gets attached to positively charged (cation) sodium. The intersection of strands is called a crosslink and a resin contains several number of crosslinks.

As the hardwater (water containing calcium and magnesium) enters into the resin tank, it goes through these beads / spheres / resin and displaces the sodium ion due the their stronger affinity to carboxylate anions than sodium. Over a period of time most of the resin will contain calcium and magnesium ions attached to them and can no more be efficient to attract calcium and magnesium ions entering into the softener via the incoming line.

At this point, the regenerations kicks-in (in some cases manual / preset or in some cases auto depending the softener controller) and salt water (sodium) from brine tank gets pulled into the resin tank and due to their sudden high concentration of sodium, sodium ions temporarily will have high affinity towards the carboxylate anions than calcium / magnesium and displaces the calcium and magnesium ions from them. The displaced calcium and magnesium ions then get discharged via the drain and resin now be ready to again attract the calcium and magnesium ions coming from the water line into the softener.

Given this, it is extremely important to select resin (or softener system) that will last for a while withstanding chlorine impact (gradual degradation of beads due to corrosive effect of chlorine making them ineffective over a period of time), water pressure variations (hydraulic shock) causing resin / beads to break, constant swelling and contraction of resin due to regeneration (osmotic shock) and eventually some of them breaking, natural wear due to resins rubbing against each other constantly and eventually breaking or becoming ineffective and heavy metal contamination (iron) etc.

The percentage of crosslinks in beads / resin will determine the strength of the resin. The higher the percentage of crosslinks, greater the strength and will last longer. Many older system have a crosslink percentage around 8 and new softeners have high efficiency resins at 10%. In a residential setup, 8% and 10% are most common while in some rare cases could be up to 20%. It is expected that 10% resins will last much longer than 8% crosslink resins and in some cases (depending on the nature of incoming water and some factors mentioned above that affect the longevity of resin) could last double the years.

Eventually all resins will give up (unless crosslinks are much higher than 10%) and at some point you will notice the degradation in softener performance i.e., not removing hardness (calcium and magnesium) effectively, discolored water, resin beads appearing in water etc. At this time, it is required to replace the resins in softener and unfortunately, it is a bit tedious process. While the resin itself is not expensive, engaging someone who knows how to do this could be expensive or one has to be handy by themselves. It is not a difficult process if one is handy. There are lots of videos on YouTube on how to do this. While the videos may not be specific to your model, the process is pretty much the same.

It is also a good idea to use resin and iron cleaning liquids on a regular basis to extend the life of the resins. There is no use of using them after it is too late. It has to be from the very beginning but on a regular scheduled basis for the life of the softener.

When buying resin (for replacing) please make sure they are specifically certified for NSF / ANSI 61 (preferably US made) and when choosing a softener make sure it comes with high efficiency resin (10% or higher). If a softener generally lasts about 15 years without needing to change resin, it did pretty well and if you maintain it well from the beginning, the chances are it will last much longer. If you are handy enough and can change the resin when it gives up, you could likely extend the softener life for another 10-15 years. There are few vendors who provide lifetime warranty on resin as well. So do your research before making a selection.

I generally prefer to stay out from making recommendation as I try to provide vendor / brand neutral information. If you want a specific recommendation or consultation specific to your need (vendor, model etc.), the please DM me or reach out to us via Otherwise, happy to answers any questions that are not vendor specific.

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