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The Hard Life of Water Softener Resin

by Sep 12, 2011

damaged water softener resin

Is your Water Softener still removing sufficient hardness, or do you see water spots or scale? Is water pressure still adequate, or does it seem lower than it used to? Do you feel like you run out of soft water in between cycles?

If you answered yes to any of these problems, your water softener resin may be worn out.

So what is “Water Softener Resin”, why does it wear out, and how long does it last?

Magic Little Beads

Water Softeners use “Ion Exchange Resin Beads” that are little spheres that range from 0.3-1.2mm in size.

These beads are made by combining strands of Polystyrene which are wrapped around in a crisscross fashion, along with Divinylbenzene (DVB) which acts like a glue that holds the resin together.

The structure of the beads looks like a ball of spaghetti, where the noodles are held together in a pattern that looks like a chain link fence.

water softener resin bead structure
The number of “links” in the bead will determine its strength, and how long it lasts.

Most modern water softeners use 8% crosslink resin. A few High Performance Water Softeners use 10% crosslink resin, which has more “links in the chain” to increase durability.

How Do Resin Beads Work?

The crosslink structure contains negatively charged “exchange sites” that hold sodium ions. As water travels through the softener, positively charged ions like Calcium, Magnesium, and Iron will stick to the exchange sites on the bead.

99% of ion exchange happens INSIDE the resin bead.

As the Hard Water Ions “stick” to the bead, the sodium ions are knocked off the bead, and into the water supply. Once the resin bead is loaded up, the softener must regenerate the beads with more sodium to continue working.

An effective regeneration is CRITICAL for long-term softening performance.

Iron Damage to Resin

Well Water in our area can have extremely high Iron levels, and most City Water sources still have low levels of Iron – even after going through the water treatment plant.

It takes 4x more sodium to clean iron off of a Resin Bead than it takes to remove Calcium or Magnesium.
Iron Damaged Water Softener Resin
If the iron is not THOROUGHLY cleaned off the bead, oxygen in the water oxidizes the Iron molecule causing it to grow roughly 20x in size. When this happens, the Resin Bead plugs up and loses a majority of its capacity.

Chlorine Damage

Chlorine is a great disinfectant that many cities use to control bacteria. It’s also a powerful oxidizer that affects rubber and plastic (like resin!).
Chlorine Damaged Water Softener Resin
Chlorinated water oxidizes and destroys Divinylbenzene (DVB) which is the crosslinking agent that gives beads their physical strength. Once the DVB bond is broken, the bead swells, and turns into a useless gel-like mass.

Here’s how you can predict chlorine’s effect on standard 8% resin life:

10/ parts-per-million (ppm) of chlorine = the expected years of service

At 0.5ppm chlorine, this is 20 years. At 2ppm, it is only five years.

It is always suggested that you remove excess (anything beyond 1ppm is excessive) chlorine prior to a softener.

Resin Takes a Beating – Literally

Water weighs 8.3 pounds per gallon. It can move through your plumbing at 8 feet per second.

Now imagine you’re running water at the bathroom sink, and you turn the water off. You don’t SLOWLY turn off the water. You pull the handle, and the water stops – quickly.

When flowing water stops immediately, it creates a shock wave that travels back through the plumbing system and SLAMS into the resin bed.

This slamming effect is called hydraulic shock. This “water hammer” physically cracks the plastic resin beads into little “fines” that eventually get flushed down the drain when the softener regenerates.

How Long Do Resin Beads Last?

Damaged Water Softener Resin
Resin life is determined by a combination of the factors we discussed: the % crosslink in the bead, iron damage, chlorine damage, and hydraulic shock.

Depending on these conditions, standard 8% resin will breakdown 2-10% each year.

Besides removing chlorine or iron, you can also improve resin life by increasing the crosslink %.

Studies show, a 10% crosslink bead will last 2x longer than an 8% bead (20 years vs. 10years).

Summary: When does Water Softener Resin need Replacement?

As resin breaks down, it releases fines that plug up the softener and result in a pressure drop. As it plugs up with iron, or oxidizes by chlorine, you lose capacity.

Lower capacity means more frequent regenerations which wastes water and salt.

If you used to regenerate every four days, it might be every three. Or maybe your hardness setting was at 15gpg, and now you have it set at 40gpg.

Instead of limping along with low water pressure, and wasting water and salt – its time to replace the resin! If the controls on the machine are old and outdated, sometimes it makes more sense to upgrade to a more efficient water softener.

If you’re having any of these problems with your current system, we offer a FREE Service Inspection to help you find out what your options are.

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