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    Understanding Water Softener Resin

    August 07, 2019 5 min read

    You've likely found this article because you're considering re-bedding your existing softener and you're trying to figure out what resin to buy (and probably how much to buy also). This article explains the general differences in water softener resin, and even a little bit about how these products are manufactured and distributed.

    Cross Link Percentage

    Water softener resin is a polymer. Polymers consist of a resin and hardener. Mixing these two components in different amounts during the manufacturing process results in resins that have different "cross link" percentages. This is literally the number of molecular cross links in the structure of the resin bead. Resins with a higher cross link percentage are:

    • physically harder
    • have a higher ion-exchange capacity (i.e. can do more softening)
    • are more resistant to being fouled by iron and manganese
    • are more resistant to being broken down by chlorine
    • are generally longer lived

    Most softeners for sale use 8% cross linked resin (Aquatell doesn't - we use 10% in all our softeners). 10% cross linked resin is a better resin for the reasons listed above, and for the cost difference between the two, we much prefer the 10% products.

    Fine Mesh vs Standard Mesh

    Mesh size refers to the dimensions of the individual resin beads. The finer the mesh size, the smaller the beads. Smaller beads can pack together more tightly so, for a given volume of resin, fine mesh will offer more ion-exchange surface area and will do more softening. However, because fine mesh resin packs more tightly, it will also reduce flow rate through the softener much more significantly than standard mesh resin. We don't love fine mesh for this reason and don't offer it as a standard product on our website. Most customers who ask about fine mesh, have been misinformed that it's more effective for iron reduction. It's not - you can read about that next. One last note here - if you take a softener that has used standard resin, and then add fine mesh to it, you have to make sure you replace the lower basket at the same time. This basket has slots in it that correspond to the resin bead size. Fine mesh resin will move right through a basket designed for standard mesh resin.

    Softener Resin & Iron Reduction

    All water softener resin can be highly effective in the removal of iron. It doesn't matter whether it's fine mesh or standard mesh. But what does matter - a lot - is the form that the iron exists in. You can read more about that here. If your water contains "clear water iron" every type of water softener resin will attempt to remove all of it. Some resin are better suited to iron removal than others though. If you have clear water iron below 2.0 mg/L, pretty much any softener resin will do a decent job. Higher cross linked resin is best.

    Above this level, we strongly recommend that you look at Purolite SST-60. It's renowned for its iron-removal capability and can quite easily handle levels of clear water iron up to 10 mg/L. But more importantly, it won't become permanently fouled in the process, as many other resins will. When using any resin in a high-iron environment it's a very smart idea to use a resin cleaner like Pro Res Care to periodically strip any residual iron off the resin.

    How Much Resin Do I Need?

    If you're thinking about re-bedding your softener (which is often an excellent way to breath life into a failing softener) then you need to know how much resin to buy. We've got a great article that will help you figure that out: Softener Tank Size. The chart in that article will allow you to match your tank size to the amount of resin you need to buy. Keep in mind that all softeners need a void space in the tank above the level of the resin. This provides space for the resin to expand when it's being backwashed. This is all built into that article. The reason we mention it is because sometimes people are confused as to why the resin we provided didn't fill the tank all the way to the top.

    Does My Softener Need a Gravel Underbed?

    The short answer is probably not. Gravel underbeds are designed to help improve the way the water is distributed through the softener tank and through the resin. This is important for softeners that contain more than 2.0 cubic feet of resin. But the vast majority of residential systems don't use more than 2.0 cubic feet and the gravel underbedding does very little (if anything) to help with performance.

    What Brand of Softener Resin Should I Buy?

    It probably matters a lot less than you think! I know, that doesn't sit well with lots of people, so I'll explain further. Water softener resin is a highly commoditized product. That means that lots of people and businesses use it, lots of companies make it, and have been doing so for a very very long time. So the sourcing of the chemical components, the manufacturing process, and quality control are all very well understood processes. This means that many different businesses, in many different countries can all produce very high quality product. More importantly, the quality of the product can be very easily inspected and verified. So there are no mysteries - there's only one way to make the product, and it either works like it's supposed to or it doesn't.

    Like is the case with most highly commoditized products, it has to be produced in very large quantities to be profitable. So there are now several huge manufacturers who make most of the softener resin that exists in the market. These manufacturers exist in China and India predominantly. These manufacturers sell their resin to brokers, who in turn sell it to water treatment companies who brand it under their own name. The end result is that there are many "brands" of resin on the market that all originate from the same factory and likely even from the same batch.

    When resin "buys" are made from a resin broker, they are often for very large quantities of resin. This causes a situation where resin often goes from being available for purchase to being out of stock for long periods. This trickles down and makes some brands out of stock for extended long periods of time.

    So here at Aquatell, for all the reasons listed above, we've chosen to sell our standard softener resins based on their technical specification, rather than their brand name. 10% or 8% softener resin purchased through us may be any of the following brands at any given time: Carbochem / General Technologies / Aldex. Again, these "brands" are all identical in quality, performance, and longevity, and we fully stand behind all of them.