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How To Use Fine Mesh Softener Resin for Iron Removal


Earlier this week, one of our customers wrote to us to ask if there was one system that could soften water and filter out iron to address an iron stain problem.

CWS Plus Softener
CWS Plus Softener w/ Brine Tank

While there is not one system that works well over the long term for both hardness and iron,  if the water comes out of the ground crystal clear, with no sulfur odor, and the pH is 7.0 or less, you can use a softener with fine-mesh resin to remove the iron and hardness, as long as some resin-cleaner is used in the brine tank (such as Res Care, or citric acid).

An iron filter installed before your existing softener is probably the best way to insure clean water over the years. Here is a diagram of a typical installation, these systems are designed to be easily installed by any plumber or person familiar with basic plumbing:

flow diagram

While we do recommend fine mesh resin for your softener if you intend to remove iron, we also want to note that there are some drawbacks to using fine mesh resin.

To start, it is a bit more expensive than standard resin. Moreover, it can be fouled rather easily: if iron sits on the resin beads for too long (i.e. if the resin is not properly, regularly cleaned) it will begin to develop an iron slime, at which point you’ll also need some resin cleaner.  Of course, this can happen with standard resin as well, but it will occur more frequently with fine mesh resin due to it being more tightly packed.  Note that such fouling will also reduce the effectiveness of your softener, because the iron in the resin will limit cation exchange (the process by which softeners remove calcium and magnesium ions and replace them with sodium ions).

You may still experience fouling of your softener’s injectors with the fine mesh resin when using it to remove iron.  This is because the iron in your water is slowly oxidized by your softener as it sucks in brine from the salt tank through a small injector or venturi.  When oxidized in this way, the iron can foul your injectors and necessitate more maintenance of the system.

Res-Up Automatic Resin Cleaner Feeder
Res-Up Automatic Resin Cleaner Feeder

However, do not worry as these problems are not too critical. The injectors can be cleaned fairly easily, and you can avoid fouling your resin with iron by using an automatic resin cleaner feeder or by running your softener’s regeneration cycle frequently, perhaps every few days.  Do note, though, that fine mesh resin requires frequent backwashing and a brine solution for the long run.

All in all, we do recommend installing an iron filter before your softener for the absolute best results.  However, if you want to stick with just the softener, fine mesh resin is definitely the better choice – just be sure to properly clean and maintain your system and you should see that iron disappear in no time.

To browse our resin and other filter media, check out our online store.  For more information about iron and water softeners, consult our free how-to guides.


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  • Clean Water Systems & Stores, Inc., Water Treatment Equipment,Service & Supplies, Santa Cruz, CA

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