Should I Install My Whole House Water Filter Before or After the Water Softener?

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This post was created in collaboration with SpringWell Water. We thank the author Tommy Stricklin who is Springwell’s chief water specialist for the time and effort he put into this. Over to Tommy!

A common dilemma for households requiring whole house water filters and water softeners is deciding which one goes first. Does it even matter? If yes, what’s the correct order to install two appliances that both purify your water supply?

If you are at a crossroads and want to settle the debate once and for all, this article is all you need.

We’ll go through all the factors/technicalities you need to consider before deciding which order to use. Keep in mind the position of these units will significantly affect their performance and effectiveness.

Key Takeaways

A whole house water filter should go before the water softener when:

  • The water supply is full of sediment, iron, or other dirt.
  • The water is highly chlorinated.
  • The flow rate required for backwashing the filter is higher than the output flow rate of the water softener.

A water softener should go before the whole house water filter when:

  • Water is clear of high levels of sediment, chlorine, or iron.
  • The flow rate required for backwashing the water softener is higher than the filter’s output flow rate.

Difference Between Water Filters and Water Softeners

Water filtration is a process that removes harmful contaminants like disinfectants and other pollutants from your water. Advanced types of water filters target chlorine, chloramine, iron, lead, bacteria, different chemicals, and so on. Unfortunately, these impurities can be a significant cause of waterborne diseases.

On the other hand, water softeners are purifiers. They don’t filter water; they only deal with hardness. Hard water implies the presence of calcium and magnesium. In layman terms, hard water is the reason for scale buildup in your plumbing and appliances, shortening their lifespan.

The main difference between a whole house water filter and a water softener is that water filters make your water safer to drink. On the other hand, water softeners target limescale buildup and embarrassing stains on clothes and dishes.

Do You Need Both?

Most people in the US are dealing with hard water. Therefore, water softeners come in quite handy. Whether you need a whole house water filter depends on the presence of contaminants in your water.

The easiest way to determine this is to take a water sample and get it tested. You could also request a water report from your local municipal office.

It helps to remember the job of a water softener, and a water filter is not interchangeable. Since each unit targets a different set of problems, you might need to install both to protect your household from water damage.

USGS Water Hardness Map

Whole House Filters: Before or After Softeners?

What came first, chicken or the egg? No one has the answer to this problem, including us. But it doesn’t mean we don’t know what will come first, a filter or a softener. It is a complicated question too, but not impossible to crack.

Consider these factors to achieve maximum efficiency from both appliances.

If you don’t want to read through detailed explanations, skip to the end for a quick checklist.

1. Municipal Water Source or Well: Where Do You Get Your Water From?

Not every household in the US gets its water supply from the same source. The two primary sources are:

  • Well water
  • Municipal water

According to the Environmental Protection Agency (EPA), over 90% of public water systems are supplied by groundwater. Nevertheless, 68% of people are provided by community water systems that mainly use surface water.

In short, urban cities rely heavily on surface water bodies. On the other hand, rural areas rely on groundwater sources.

The source of water and its quality will determine whether you need both appliances and in what order they would be placed.

2. Sediment Levels

If your source of water is a well, chances are, you are dealing with high levels of sediment. Water that is full of debris, sand, dust, clay, and silt not only makes your water “turbid” and unpleasant to drink but also clogs the pipes to your water-based appliances.

If you are dealing with dirt-laden water, it will literally kill your water softener.

The logical action in this scenario is to install a pre-filter that is sediment-based before your softener. This will filter all the large particles, and your softener won’t clog as often. In addition, it will reduce the workload on the system and protects the resin media inside.

If you are lucky, and the turbidity levels of your well water are below average, a softener will do just fine when installed first in line before the water filter.

On the other hand, municipal water doesn’t usually have a high level of turbidity and is generally safe for use in a water softener without prior treatment.

3. Chlorine Levels

Most if not all utilities in the US add chlorine or chloramine to your water to disinfect it. They kill harmful parasites, bacteria, and viruses and makes it safe for drinking and residential usage.

Some homeowners assume that their water softener will take care of chlorinated water, but unfortunately, chlorine is another no-go for such systems.

Why is it a cause of concern? You may find yourself asking what harm chlorine can do if it is widely used to disinfect our water supplies.

Well, moderation is key to using chlorine for a household water supply. You must know the chlorine level in your water before you decide if it can flow directly into your water softener. When water with a chlorine level above 1.0 ppm flows through the softener’s resin bed, the chlorine will oxidize the resin beads.

As a result, chlorinated water affects the strings of said beads and causes them to fragment. Not only does this negatively impact softening capacity, but it also cuts the life of your resin in half.

Tip: Most water softeners in the US typically use 8% crosslink resin. But 10% crosslink resin is slightly more robust and has a better chance of tolerating chlorinated water.

But regardless of 8% or 10% crosslink resin, your softener is better off when installed after a whole house water filter when dealing with elevated chlorine levels. Of course, the filter must be capable of removing the disinfectant. Carbon-based systems are best used for this.

4. Iron Levels

Do you regularly see unsightly red stains on your clothes, sinks, or tub? If yes, then you are dealing with high iron content in your water.

Similar to chlorine, water softeners are not equipped to deal with water with such high levels of iron (or manganese).

If iron concentrations are between 3-5 ppm, a standard 8% crosslink resin will do just fine. On the other hand, higher iron content means you need a fine mesh resin (might be expensive).

Another smart option is installing a whole house iron water filter that reduces dissolved iron and other heavy metals before your water softener.

Water Filter Cartridge

5. Backwashing: Understanding Whole House Water Filtration and Water Softening

The backwash phase is the first stage of regeneration in a water softener. Simply put, water runs backwards through the resin tank. This process removes sediment and other dirt as well as hardness minerals from the resin bed. The goal: Restoring the softening capacity.

The backwashing process requires a high-enough flow rate to expand the resin bed and rattle the bonds of each bead.

If a water softener is installed after a water filter, the filtering stages may reduce backflow water pressure. And if the backwash flow rate/pressure drops below a certain point, the water softener cannot rinse properly. The resin bed will remain contaminated and not work efficiently. As a result, it will clog and foul even more, failing eventually.

Therefore, your whole house water filter should allow a flow rate at least as high as the backwashing rate required by your water softener.

Some specialized whole house filters that target iron for example also need to backwash and require specific flow rates to backflush effectively. In this case, the water softener, when installed before the water filter, needs to allow a minimum flow rate equal or higher to the backwashing rate of the filter.

In both cases, it’s essential to compare the water flow rates and required backwash rates of both appliances. Failure to take this factor into account will result in improper backwashing and ineffective systems.


Here is a quick guide to help you.

Whole house water filters go first when:

  • The water supply is full of sediment
  • Water is highly chlorinated
  • The water flow rate required for backwashing the filter is higher than the output flow rate of the softener.

Water softeners go first when:

  • Water is clear of high levels of sediment, chlorine, or iron (touchwood!)
  • The water flow rate required for backwashing is higher than the filter’s output flow rate.

If you have any questions about installing a whole house water filter before or after the water softener, please don’t hesitate to leave a comment below!

About the Author Tommy Stricklin

Tommy Stricklin is SpringWell Water’s chief water specialist with more than 2 decades of experience and knowledge within the residential water industry.
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Tommy Stricklin

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Leave a Comment:

Tom Russell says November 22, 2021

Very happy to find your site and articles on sediment filters! Logic tells me the filter should be after the water well and before the pressure tank, I have researched this topic for a month. I’ve read many people think this is not the best location. I have a HAGUE water system and really don’t want all those particulates collecting in my tank. You have reinforced my thoughts as being logically correct. I do have a reverse osmosis system for drinking water so I’m sure when I install my new tank and system with Uponor PEX A and a recommended sediment filter I’ll have the system as I desire it for best service and protection. I will pay close attention while in the backwash process.
Thank You…Thank You! Tom Russell in Tennessee

Paul Khalil says July 6, 2022

I had a whole house filter before the softener and two after the softener. I noticed green algae on the two filters after the softener . also I see slimy soil in the bottom of my toilet. I have disconnected the three filters and now I am at the point of not knowing what to do. I live in Anaheim where the water hardness is at 29

    Gene says May 1, 2023

    Hi Paul,
    When was the last time that you maintained your filters and softener? If there’s algae in your water, you could kill them using shock chlorination.

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