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Can I Connect the RO with a Water Softener?

par Dr. Jonathan Doyle - Updated May 06, 2021
Some customers who already own a water softener at home often come up with a question: If I already have a water softener, can I also use an RO system?
A short answer is, if you want to additionally remove the other contaminants that a water softener doesn’t remove, then yes. But if you want to remove the salty taste of the softened water, we would not recommend a RO system.
If you want to know why, keep reading this article to discover the reason.

What Is Water Softener?

A water softener is one of the most effective household water filtration systems designed to remove “hardness ions” - mainly calcium and magnesium minerals, leaving you with cleaner and fresher water.
There are mainly two types of water softener. Although both types will reduce the hardness ions in your water to leave you with beneficial softened water, they do this differently.

Salt based (Ion- exchange) water softener

Salt based water softener turns “hard” water into “soft” by means of ion-exchange.
Ion exchange is a reversible chemical reaction where dissolved ions are removed and replaced with other ions of the same or similar electrical charge. Salt-based water softened required to refill salt periodically, exchanging the “hardness ions” like calcium and magnesium ions in the water with sodium or potassium ions to make the water “soft”. That is why the water from the salt based water softener would taste salty.

Salt-free water softener (Water conditioner)

Salt-free water softeners (water conditioners) are alternatives to the ion-exchange models. They use a softening process called Template Assisted Crystallization (TAC) instead of ion exchange to convert the hard minerals in the water into crystals. Despite this difference, salt-free water conditioners are classified as water softeners because they also reduce the effects of hard water and produce soft water.
These water softeners do not require any salt, maintenance, or electricity, making them much easier to manage than traditional salt-based water softening systems.

What Is Reverse Osmosis System?

Reverse osmosis water filtration systems adopt innovative RO membranes with a 0.0001-micron pore size, which is 100,000 times smaller than the diameter of a human hair. Thanks to the tiny pore size of the RO membrane, the RO water filtration system can effectively remove various impurities in water, including sodium, chromium, chloride, copper, lead, arsenic, pesticide, fluoride, radium, sulfate, calcium, magnesium, potassium, nitrate, and phosphorous, among others.
The RO system distinguishes itself from other water purification systems with an RO membrane, which can remove bacteria and viruses in water. However, as water has to pass through the multi-stage filter media, the flow rate might be slightly impacted, resulting in a slower flow rate than the water softener.

What’s the Difference Between Water Softener and Reverse Osmosis System? 

Generally speaking, water softeners usually serve as a whole house filtration system, installed at the point of entry and soften water for the whole house. However, RO systems are usually installed at the point of use like under a sink  and only provide purified water for drinking and cooking via a separate tap.
Reverse osmosis (RO) systems can eliminate almost all contaminants in water, but water softeners just reduce hardness ions like calcium and magnesium in your water to provide a better taste.

Can I Connect My Water Softener with a Reverse Osmosis System to Remove Other Contaminants?

Yes, if you worry about the other contaminants still present in your softened water, it’s advisable to install a RO water purifier additionally, which helps to remove various other harmful substances that water softener cannot remove, such as heavy metals, pesticides, VOCs, etc.

Can I Connect My Salt-Based Water Softener with an RO System to Remove Sodium?

However, if you are bothering with the salty taste of the softened water, we do not suggest you remove the taste with an RO System. This is because when water passes through, the water softener increases the salt concentration, making it much saltier than the source water. Although the RO water purifier has removed up to 90%  of the sodium from the softened water, you will still taste the salt.
Thus, it is not advisable to connect an RO to remove the sodium.