Are All Reverse Osmosis Filters the Same?

Are All Reverse Osmosis Filters the Same?

Homeowners concerned about their water quality and safety, due to potentially high levels of lead, arsenic, and other contaminants, use reverse osmosis (RO) filters to ensure pure water for consumption. However, are all reverse osmosis filters the same?

All reverse osmosis filters are not the same. RO filters can be found in several configurations with singular, dual, or triple filtration functionality. They can have different inlet sizes such as 1/4”, 3/8”, 1/2”, and 3/4”, and can be of different types. Lastly, they can vary in length and diameter.

If all RO filters are not the same, how do you know which one you need when it’s time for a replacement? Well, in this article, we will learn more about RO filters and which ones you should opt for depending on the system you have installed and the quality of your domestic water supply.

Read my comprehensive article about reverse osmosis.

The Different Types of Reverse Osmosis Filters

A reverse osmosis filter removes heavy metals, hard minerals, and 99.9% of all pollutants found in water.

The semipermeable membrane is just one of the filters involved with water purification. Although it is the most powerful, the other filters are just as important.

A high-quality RO system would include all of the following filters while other more inexpensive models might be missing one or two of them.

  1. Sediment Pre-Filter
  2. Activated Carbon Filter
  3. Reverse Osmosis Membrane
  4. Activated Carbon Post Filter
  5. Remineralization Filter

Let’s get into a bit more detail and learn more about these filters and the stages each one goes through during the RO process:

Stage 1 – Sediment pre-filter

A sediment pre-filter is a mechanical filter. It is made up of a super-fine polypropylene cartridge that removes sediment particles as small as 5 microns. All kinds of grit, mud, rust, algae, and dust are removed from the water before it even reaches the main filter. By doing so, it decreases the stress on the semi-permeable membrane, extending its life.

Stage 2 – Activated carbon pre-filter

After passing through the sediment filter, the water is met with a high-grade granular carbon cartridge. This filter weeds out as many impurities as it can before the water reaches the semi-permeable membrane.

The build of this filter is effective at removing chlorine and various other chemicals found in the water. It is also at this stage that all the funky tastes and odors are purged. The removal of chlorine from the water also protects the membrane from degradation.

Stage 3 – RO membrane

An RO membrane is semi-permeable with its filters having a pore size no bigger than 0.0005 microns. With such an ultrafine makeup, the membrane can filter out microorganisms from the water along with heavy metal complexes such as aluminum, mercury, lead, etc.

Except, for a minuscule number of contaminants, nothing remains in the water once it has passed through the membrane, not even colloidal matter, cysts, fluorides, sodium, or any mineral ions. Only water molecules come out on the other side, in pure H2O form!

Stage 4 – Carbon polishing post filter

Now that all the physical contaminants are removed, this post filter drives out any unwanted taste and odor from the water. This filter is the final post, to make sure that the water is free from all impurities once and for all and is safe and healthy for consumption.

Stage 5 – Remineralization filter

Not every microparticle in the water is bad. As a matter of fact, some of those are nutrients and essential for human health.

This filter allows the water to regain calcium, potassium, magnesium, and other trace minerals that our body desperately needs.

Calcium in water is great for our bones and teeth, whereas magnesium acts as an activator of more than 300 enzymatic reactions. Sodium and potassium assist the muscles and nerves to function properly.

The lack of these minerals in the water can lead to poor health, and most modern RO systems have this additional filter in place.

Read my article about remineralizing your reverse osmosis treated water.

How To Choose a RO Filter That Is Right for You

There are three methods that you can use to help choose the right filter for your RO purification system:

Picking the right configuration

You can choose a standard-sized filter if you have a basic RO unit.

  • 3-stage RO system – two vertical filters and one horizontal filter on top

This is the universal RO shape and design. It uses two pre-filters with a standard size of 10″ x 2.5″. The horizontal filter, which is the RO membrane, comes in an 11″ x 2″ size.

  • 4-stage RO system – two vertical filters and two horizontal filters on top

This 4-stage RO system also uses standard-sized filters of 10″ x 2.5″ and 11″ x 2″. It has an additional carbon filter on top of the same standard size.

Some filters can also have different inlet sizes for connecting tubes. Always make sure the filters you buy have the same inlet size as the ones you currently have on your RO unit.

Identify the model of your RO system

If you are unsure about the type of your RO system and the size and dimensions of the filters, identify the brand and model number.

The model number can be found on the metal of the plastic manifold that is holding your filter housing in place.

Once you have the model number simply look it up and you’ll find the complete details of the filter replacement.

Purchase directly from the system manufacturers

Numerous manufacturers plan the shape and build of their RO system in such a way that it can only fit their exclusively manufactured filters. In that case, you’d have to purchase the replacement kit directly from the manufacturer.

Frequently Asked Questions

Can reverse osmosis purify water from a well or other untreated sources?

Yes, an RO filter can purify water from a well, even if it is salty. However, an RO filter does not offer 100% filtration of bacteria, viruses, or cysts that can still exist in well-extracted water. This is why you should always conduct a water test to ensure that the treated water is safe for drinking.

Q) Why is a reverse osmosis system always paired with carbon and sediment pre-filters?

The RO membrane is not very effective at removing organic compounds. To cope with that, activated carbon filters are added. The sediment pre-filter is also a necessary addition so that it can protect the membrane from getting clogged by larger sediments. Both the pre-filters ensure cleaner water and a longer lifespan of the membrane.

Final Thoughts

To wrap everything up, most reverse osmosis systems have a universal shape, and their filters are of the same standard size. However, these filters do not necessarily fit all RO systems. If you are still uncertain, consult with a water treatment expert.

Chief Guru

Richard Boch is a chemical engineer responsible for designing water filtration systems for industrial and residential customers. He has more than 20 years of experience with ion exchange, activated carbon, and reverse osmosis. Richard's expertise has made him a go-to source for municipalities and businesses looking to improve their water quality. When he's not working, Richard enjoys spending time with his wife and two young children. You can also follow him on LinkedIn, Twitter and Facebook.

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