Guide: Whole House Water Filter Before or After Water Softener?

Author: Jason Hollow - Published: 2021/09/15 - Updated: 2021/09/15

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Water quality over the US has its fair share of ups and downs. Where some people would step back at the thought of drinking tap water, others happily hold a glass to the faucet and chug it down.

If you belong to the former group, you may need both a whole house water filter and a water softener to purify your water supply. These two units work simultaneously to filter and soften water to make it fit for residential usage.

A common concern that arises in this situation is which one should be installed first? The answer lies in the quality of your water and the contaminants you are dealing with. Let’s walk you through all the factors that you must keep in mind before calling your technician.

So, here is our guide answering the question, should you install your whole house water filter before or after the water softener?

The Difference Between Water Softeners and Water Filters

Water filtration is a complex procedure that integrates rejection, adsorption, ion exchange and other methods to remove harmful water-borne contaminants.

In other words, the main goal of filtering water is to protect your health and also to improve how your water tastes and smells. But, it simply has almost no effect on hard water, which is full of minerals.

On the other hand, water softeners are not meant to filter any harsh chemicals, heavy metals, fluoride, etc. Instead, they purify water of hardness-causing minerals, primarily calcium.

It’s essential to mention here that these minerals do not pose any health risk. Quite the opposite, they are beneficial to your health and make your water taste better.

Why bother, then? There’s plenty of good reasons: First, hard water leads to a buildup in your pipelines and water-based household appliances. Second, the scaling results in lower water pressure and premature failure of said components.

Moreover, hard water also leaves stains on sinks, tubs, and glassware as a white powdery residue. Noticed skin dryness and brittle hair lately? Hard water is the probable culprit!

In essence, the main difference between water filtration and water softening is that a water filter protects the health of your family, while a water softener protects your plumbing and household appliances.

Combining a Filter with a Softener

You see, remarkably 85 percent of the US has hard water.[1] So apart from the 15% population, most Americans do need a water softener in their house.

Whether you also need a water filter or not can only be determined by analyzing the presence and level of contaminants in your water.

If your water is high in iron, lead or other heavy metals, or you are dealing with pesticides, PFAS or other harmful chemicals, or your water smells and looks awful, you need a whole house water filter.

Since whole house water filters and water softeners serve two opposite purposes, you may need both in order to have a dual line of defense against minerals and contaminants.

Install Whole House Water Filter Before or After Water Softener?

Whole House Water Filter Before or After Water Softener thumbnail

But should you install your whole house water filter before or after the water softener?

Does it even matter, you may ask? Yes! The performance of the two systems can be greatly affected by the order in which they are installed.

The installation is unique for every household as it entirely depends on your water supply. Here are a few factors that will help you determine which goes first: water softener or water filter.

Skip to the table at the end for a quick overview!

The Water Source: Tap Water vs Well Water

Water in the US comes mainly from two sources:

  • Private well water
  • Municipal water

Over 70% of freshwater supplied by water utilities in the US comes from surface water bodies. The rest, 30%, are from groundwater. The composition of water from both sources differs significantly.

It is generally believed that water supplied from underground wells (very deep ones) tastes better and is less contaminated than city water. Well water is usually fresh, full of minerals, and high in nutrients, but it is also generally laden with sediment and possibly heavy metals like iron.

Whereas city water is filtered to remove sediment among other stuff and treated with disinfection chemicals that kill bacteria, parasites and viruses.

Bottom line: The source of your water and its composition will considerably affect how to best set up a whole house and a water softening system.

Chlorine

Chlorine and chloramines are disinfectant chemicals added at the water utility to kill several disease-causing microorganisms.

Unfortunately, it gives an unpleasant taste and smell to the water, which is the number one concern of most homeowners.

Apart from this, chlorine is a no-go for a water softener’s resin. This is because the resin used in water softeners is sensitive to high levels of chlorine.

While chlorine levels up to 4 ppm/L are considered safe for residential usage (drinking and cooking)[2], any concentration above 1 ppm will oxidize resin beads causing permanent damage.

Besides reducing the softening capacity, chlorinated water severely impacts the life of the resin. Therefore, you must find out the level of chlorine in your water before deciding which unit goes first, water softener or water filter.

Some manufacturers claim their softeners boast 10% cross-link resin compared to the standard 8%. 10% cross-link resin is definitely sturdier and better adapted to tolerating chlorinated water.

Unfortunately, the difference between the two is negligible. Therefore, when dealing with high levels of chlorine, it’s wise to install a carbon-based whole house water filter before your softener. The filter can lower chlorine content in your water before it reaches the softening stage.

Sediment

Sediment level refers to large particulate matter, including dirt, silt, rust, and dust that you can see floating in your water when you look carefully.

High levels of sediment are usually a common issue with water from a private well. Some people have even observed and cited that their water supply was “muddy.”

Besides being unsuitable for drinking, turbid or muddy water wreaks havoc on a water softener, chokes the pipelines, and fouls the ion exchange resin.

Technically, a sediment pre-filter is essential to filter out contaminants so the softener can do its work effectively.

However, if your water has low levels of sediment, the softener won’t need a sediment pre-filter.

Luckily, municipal water has already been filtered and has low or no levels of sediment. So, you can safely install a water softener first in line.

collection of whole house water filters

Iron

Elevated levels of iron and rust can be damaging to your gastrointestinal system. But it doesn’t end there. High levels of iron are a no-go for water softeners as well.

As long as the level in your water is below 5 ppm, a softener with standard 8% cross-link resin won’t get harmed. However, if it’s higher, you will need a fine mesh resin (more links in the chain) which is better adapted to treat iron ions.

Another reasonable solution is to use a whole house iron filter before the water softener.

Backwashing

To understand how water pressure is essential to the performance of both a whole house filtration system and a softener, we will first go through the basics of backwashing.

Backwashing is the process that cleanses the resin bed of a water softener by reversing the flow of water through it. It is the first step of the regeneration cycle. And many water filters use it as well in order to flush accumulated contaminants out of their filter media and down the drain.

Without backwashing, a water softener would lose its softening capacity just like a whole house water filter would lose its filtration capabilities.

The process of backwashing requires a high water pressure to move through the resin bed/filter media and remove all the dirt and mineral ions.

Here is the tricky part! Some whole house water filters result in a considerable drop in water pressure. This is because they limit the flow of water. Thus, if you install a water filter before the water softener, the latter might not be able to backwash properly. Over time the resin will foul. Moreover, the water softener will slow down, waste more water, require more salt and still not perform as desired. Not to mention, you will end up with costly repairs and maybe replacements.

Exactly the same holds true if a water softener that doesn’t allow a very high flow rate is installed before a backwashing whole house water filter. The water softener affects the filter’s backwashing process which could lead to improper flushing of the filter media.

So how to work around it? Ensure that the water filter’s output rate is more or equal to the water pressure required by your softener to backwash, and vice versa.

In essence, the output water flow of the treatment system first in line should be enough for the system second in line.

In Summary

Still confused? Let us simplify it for you!

Water softeners go first when:

  • Water has low levels of sediment, iron, and chlorine.
  • The water pressure required for backwashing the resin is higher than the output rate of the whole house filtration system.

Whole house water filtration systems should be installed first if:

  • You are using well water that is full of sediment.
  • The water is highly chlorinated.
  • The water pressure required for backwashing the filter is higher than the output flow rate of the softener.

Conclusion

In conclusion, filtration cleans water from possibly harmful contaminants and improves taste and odor.

Softening on the other hand removes hard water minerals primarily to eliminate scaling in pipes and appliances.

You might need both a whole house water filter and a water softener.

Which to install first depends on your water quality – think sediments, rust, and chlorine – and also on the required backwashing flow rates of each system.

Further Reading

Resources

Meet Jason Hollow

Jason Hollow Jason is the founder of Water Masterz and head of content creation. After six years in the industry, he has tremendous knowledge and first-hand experience on all things related to water treatment.

His credo: Not a single American should have to drink unhealthy water at home.

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