How Does A Whole House Water Filter Work (2021 Guide)

Do you want to learn how whole house water filters work?

These water filtration system are installed right after your main water shutoff, and they can provide purified water to every faucet, AND protect your pipes at the same time.

In this guide, I will go over...

  • Exactly how these centralized home water filters work
  • The different types of filters used in these systems
  • How activated carbon filtration works
  • Why I always recommend installing THREE shutoff valves and a bypass pipe

Let's get started with this guide!

how does a whole house water filter work

How Do Whole House Water Filters Work?

Whole house water filters are devices that will filter your entire home's water supply. These central water filters are usually installed right after the main water shutoff valve.

You want to install a whole house water filter as close to the main water shutoff as possible, and prior to any plumbing branching to your fixtures or appliances.

Whole House Water Filters Vs Point-Of-Use

The problem with point-of-use water filters is that they only work for one plumbing fixture. If you install an under sink water filter for your kitchen, it will only filter the kitchen sink's tap water, but none of the other fixtures, appliances, or plumbing in your home.

The nice thing about whole-house treatment units is that they provide clean, purified water throughout your entire home.

They will also help prolong and increase the efficiency of your appliances such as the water heater, dishwasher, coffee maker, shower head, and other water appliances.

Read Also: What Are The Best Whole House Water Filter And Softener Combos?

How Do The Different Filters Work?

There are very simple whole house water filters that have only one filter, and it is used to remove only one type of impurity such as chlorine.

Multi-Filter Systems

But there are also whole house water filters that have 2, 3, or even 4 filters in a series. These 3 or 4 filter systems may be able to remove iron, fluoride, chlorine, sediment, and a whole host of other contaminants.

Each filter has a specific purpose in the system and removes one or more types of impurities.

Interchangeable Filters

With some whole house filters, you will be stuck with one type of filter from the manufacturer. If the whole house water filter you buy has a custom sized filter, then you will be stuck buying the filter from that one brand.

However, some whole house filters have standard and interchangeable filters such as the 'big blue' whole house filters.

The big blue filters have standardized filters that you can buy from different companies, as well as filters that have different filtration designs. You can swap out a big blue activated carbon filter for an iron reducing filter or even a fluoride reducing filter.

Read Also: What Are The Best Whole House Water Filters To Remove Fluoride And Chlorine?

How Do Granulated Activated Carbon Filters Work?

The most common type of filter for whole house water filters is granulated activated carbon filters or GACs.

These filters are composed of small pieces of carbon that are extremely porous and have a strong molecular bond. Any impurities in the water will stick to the carbon (a process called adsorption) and give you cleaner and better tasting water.

The biggest focus of these filters is chlorine reduction and usually used with city or municipal water (as opposed to well water). Basically, if you want to improve the taste and smell of your water, then a GAC whole house filter is the way to go.

In addition to chlorine, activated carbon can remove or greatly reduce pesticides, herbicides, volatile organic compounds, and a bunch of other chemicals.

Read Also: What Are The Overall Best Whole House Water Filters?

how does a whole house water filter work

How Does A Water Softening Filtration System Work?

After activated carbon filters, having a whole house water softening system is also very common whole house water filter in the homes I inspect.

Water softening filters are designed to remove or reduce hard minerals in your water especially calcium and magnesium. These minerals cause scale buildup in plumbing pipes, appliances, fixtures, and can damage clothing, skin, and hair.

The most common type of water softener is the salt based system, and it uses two tanks for softening water, a resin bead tank and a brine tank.

The ions in the resin bead tank attract and remove hard minerals from the water. But eventually the resin tank will be at capacity, and then salt water from the brine tank 'flushes' the resin tank of the hard minerals which goes down a drain.

This is known as a regeneration process and afterwards the resin tank is able to remove hard minerals again.

Read Also: What Are The Best Iron Filters For Well Water?

How Does A Sediment Filter Work?

Sediment whole house filters remove things like sand, rust, dirt, and other large particles in the water.

Sediment-trapping devices are frequently the first filter if the system has a multi-filter system. They are also known as pre-filters because they are commonly installed just prior to the activated carbon filter.

The nice thing about sediment filters is that they will prolong the life of the downstream filters and help them from getting clogged. Sediment filters are also usually replaced much more frequently than other types of filters.

Read Also: What Are The Best Whole House Water Filter And Softener Combos?

How Do Shutoff Valves Work?

Shutoff valves are plumbing devices that can close or open water flow in a pipe, and shouldn't be confused with a water meter which simply measures water flow.

It is a good idea to have a shutoff valve installed on both sides of the whole water filter system.

If you have to change the filter, or do some type of maintenance on the system, shutoff valves will make the process significantly easier. When you have shutoffs on each side, this will prevent water from draining out of the other piping.

Read Also: What Are The Best Whole House Water Filters To Remove Fluoride And Chlorine?

How Does A Bypass Pipe Work?

Another thing to consider is the installation of a temporary bypass pipe and shutoff valve.

A temporary bypass is a short run of piping that goes around the whole house water filter. There will also be a single shutoff valve in the middle of the bypass pipe.

When the whole house water filter is working properly, the shutoff valve in the bypass pipe will be closed (perpendicular to the pipe). But when you need to change a filter or do maintenance, you can open the bypass pipe so that you will still have water access in your home.

Read Also: What Are The Overall Best Whole House Water Filters?

Final Thoughts On How Whole House Water Filters Work

Whole house water filters work by filtering your entire home's water supply. They are usually installed just after your main water shutoff where it comes in from the street or well.

Whole house water filters can use a wide variety of filters that are designed to remove impurities such as chlorine, rust, sand, fluoride, volatile organic compounds, pesticides, hard minerals (scale), herbicides, and other contaminants.

The filter cartridges of whole house water filters usually have to be replenished or replaced anywhere from a few months and all the way up to 5-10 years. Pre-filter or sediment filters usually have to be replaced every few months.

Most counties and cities will require plumbing permits to install a whole house water filter due to the piping required.

Whole house water filters can cost anywhere from a few hundred dollars and all the way up to thousands depending on the quality and extent of the system including labor.

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Arie Van Tuijl

Arie Van Tuijl

I am a licensed home inspector in two U.S. states and the founder of Home Inspector Secrets. After performing hundreds of inspections, and seeing thousands of house defects, I realized people would love to have an online resource dedicated to home maintenance. I write detailed home guides and product reviews sprinkled with inspection tips. You can read my bio here.

About Home Inspector Secrets

Home Inspector Secrets is an online resource for owners, buyers, and sellers to understand all aspects of home maintenance. We have detailed home guides, product reviews, inspection advice, and much more.

Other Home Guides

Looking to learn more about home maintenance? Check out our other informative home product reviews and guides!