A reverse osmosis (RO) system works by sending water through a series of filters and semi-permeable membranes to block/remove unwanted molecules.

On the surface it’s a pretty simple concept, right? You send water with unwanted particles through a reverse osmosis system and it comes out of the tap as pure water. Simple- or is it?

You’d be surprised to learn all the steps your water goes through to get clean. You know water goes through filters, but do you know what those filters actually do? In this article, we’ll be going over what a reverse osmosis water filter does, what it’s made out of, and what which filters you need for you, your pets, your plants, and even for use like showers and washing your car.

What is a Reverse Osmosis Filter and What Does it Do?

Simply put, an RO filter is one of the parts in a complete RO system that helps remove unwanted particles and molecules from water. Whether it’s hard particles like dirt or metals or contaminants like chlorine and pesticides, each RO filter has its own job to do in order to give you clean water.

While we wish there was an all-in-one filter that can remove chlorine, pesticides, sand, and metals from water, trying to filter out everything all at once will not only leave particles in your water, you’d also damage the filter. Not only that but if there was a filter that could do it all, it would be really big and crammed with more equipment than would be helpful.

You see, the big difference between RO filter systems and carbon filters (like a Brita tap/pitcher or even a 2-stage RO system for example) is that carbon filter and 1/2 stage RO systems don’t get rid of half as many as the filters of a good RO system.

For example, a standard Brita will filter out a few heavy metals and some chlorine which is great for taste and visual appeal. Elements like pesticides and rust, however, can’t be filtered out. On the other hand, there’s an RO filter for nearly anything you want to be removed from your water including rust, herbicides, silt, and other harmful particles carbon filters can’t get to. When you have a few of these filters in your reverse osmosis system, you’ll be getting the clean water you want every time you turn the tap.

What Makes a Filter Work, Anyway?

When you hear the word “filter” you probably think of something metal or plastic you can put water (or anything, really) through and remove an object from it. That’s sort of what RO filters do for your water, but instead of just metal or plastic, there are a variety of materials used to keep unwanted particles in check. From plastic to charcoal to coconut, any given filter will have different materials for specific particles that need to be removed.

There are a number of filters out there with lots of different materials used to filter out chemicals, metals, and dirty molecules from your water. We’ll focus on some of the most common filters out there and what they use to get those nasty atoms out of your water:

Sediment filters help catch solid particles before water reach the tap. Well-performing sediment filters will block suspended solids like sand, silt, rust, and other sediments as small as 1 micron from making it out a reverse osmosis system.

These filters are often made tightly wrapping lots of super-porous polypropylene. When water is pushed through the filter, the tiny holes in the filter let water out while holding big particles back.

Carbon filters help absorb organic contaminants like chlorine, pesticides, herbicides, and other chemicals that lead to bad taste and smell.  Unlike other filters that physically block out pollutants, a carbon filter is made with carbon that soaks in those chemicals the best.

For a carbon filter to work, you’ve got to make sure it has the correct carbon source to do the job. That’s why in any given RO system you’ll see one or both of the following:

  • Granular Activated Carbon (GAC) filter: These filters are made of granular carbon, often made with grains of charcoal and coconut to keep out larger particles in water.
  • Carbon Block Filter: This type of carbon filter uses similar carbon made out of charcoal and coconut, only this material is finer in order to absorb those hard-to-filter particles in your water.
  • Carbon Postfilter: This filter is just like block and GAC filters, only this type of filter specifically helps absorb all those other contaminants the other two carbon filters may have missed right before water exits the tap.

Reverse Osmosis Membranes are made with tightly wrapped semi-permeable material (usually polypropylene) and designed to remove the dissolved solids and tough-to-remove impurities other filters couldn’t get to. Water flows into the membrane, is forced through the membrane, and comes out ready for one last cleaning by the Carbon Post filter.

The great thing is about RO membranes is that contaminants like lead, asbestos, bacteria, and certain pharmaceutical agents other filters can’t get rid of will be filtered out here.

Keep in mind that these are just some of the filters RO systems use. There are plenty more that have different functions, like helping kill off bacteria and even adding alkaline elements into your water (because some sediments are actually good for you).

What filters should you use for reverse osmosis?

Now that you know what sort of filters are out there, what they’re made from, what how they benefit your reverse osmosis system, let’s talk about what filter(s) you should be using.

Watering Plants– Believe it or not, plants enjoy fresh water just like we do. However, they don’t need it as clean as we like it. In fact, filtering your water too much will have an adverse effect on plants. Completely emptying your water of virtually all particles, there’s nothing in the water plants can thrive off, especially if you’re growing in soil that has little nutrition.

Plants need elements like calcium to grow, and that’s found in tap water. Instead of using an entire 5+ stage RO system, you really only need sediment, de-chlorinator, and carbon filters. At most, you’ll need a 3-4 stage reverse osmosis system to assure your plants get the water they need without any of the acidic chemicals that cause damage to your plants.

Personal Use (non-consumption use)- Your hair and your car have something in common: you’ve probably been washing both with the same quality water. You may not notice because, with everything you do all day, shower/bath water and the water you use to wash your car are probably not things you think of.

But have you ever gotten out of the shower with thick, hard-to-manage hair? Or like somehow you didn’t get all the way clean? How about washing your car just to see streaks everywhere when it dries? That’s because you have hard water, and all those elements that make your water taste and smell bad are now all in your hair, all over your body, and all over your car.

For the most basic of needs- like washing clothes, dishes, and cars- you can go with the same sediment and carbon filters you’d give plants and get fantastic results. Your clothes will feel softer, and your dishes and car won’t leave streaks when they’re dry.

Now for your hair and body, we suggest going with a shower filter like the NU Aqua 12 Stage Shower Filter. Quality shower filters like these are made with at least 12 elements to keep water soft while keeping your hair and skin oils safe. Showers are refreshing, but a great shower will make sure your hair and skin stay healthy and keep you smelling great and feeling even better.

Consumption by Humans and Animals

Let’s talk big game: drinking water. It’s well known that clean drinking water is good for humans, and there’s evidence showing that clean drinking water has the same benefits for our pets. That’s why it’s important to use a reverse osmosis system that uses at least sediment and carbon filters, as well as reverse osmosis membranes.

With that in mind, you should also consider your source of water to determine how many stages of filtration you need:

  • City Water- 5-Stage reverse osmosis systems are great for homes that use city water. This water’s treated with chemicals to make it safe for consumption without filtration. That means with an RO system, city water can become both safe to drink and tasty, too. These systems offer sediment filters to get larger particles out of our water; 2x carbon filters to help soak up organic contaminants like pesticides and chlorine; along with an RO membrane to help filter any last particulates hanging around and a carbon polishing filter to help clean out anything left that could discolor your water and make it taste funny.

When water gets that clean, sometimes you can lose out on important minerals found in city water. That’s the great thing about 6-stage RO systems: you can use all of the filters of a 5-stage system but with the added benefit of a 6th Alkaline filter.

Alkaline filters like those from NuAqua use a 5-stage filtration process that increases natural minerals like calcium, iron, zinc, magnesium, copper, and selenium that are good for our health and digestion. It also increases the availability of antioxidants in your water while oxygenating it to provide the healthiest and most mineral balanced alkaline drinking water available for your body.

  • Groundwater- If you’ve got a well or a pump providing water to your house, you’ll not only need to treat your water before drinking it, you’ll also need an additional UV filter. Groundwater from a well or a pump usually has harmful elements in it filters can’t soak in or hold back. In those cases, you’ll need to treat and sterilize your water before drinking itThat’s why you’ll need a 7-stage filtration unit like the NU Aqua Platinum Series 6 Stage UV Ultraviolet 100GPD RO System, complete with sediment and carbon filters, RO membranes, a polisher, an alkaline additive, and most important: a UV filter. When you use treated groundwater, you’ve still got microorganisms that all of your other filters missed. A UV filter will sterilize your filtered water and eliminate up to 99% of harmful bacteria, viruses, and microorganisms for safe water you and your pets can enjoy.