Water Softener 7/10: Water Softener vs. Reverse Osmosis

Following are few questions homeowners ask when selecting components for their residential water purification needs i.e.


What is the difference between Water Softener and Reverse Osmosis System? Do I need both Water Softener and Reverse Osmosis?


Please note, each individual is different and so are their needs. While many may find water from city is fine for drinking , others may view it differently depending on their own need and their family needs . While there are several options available in the market for drinking water, following is meant for those who are interested in knowing little bit more about Reverse Osmosis system for their drinking water needs.


I have attempted to explain why water softener is needed, what it does and benefits etc. via one of my posts here. In essence, water softener's main purpose is to remove hardness (mainly calcium and magnesium) from water to protect water lines & appliances from scale buildup and to provide other benefits mentioned in the above post.


However, it does not remove any other common contaminants like metal ions, aqueous salts including sodium, chloride, copper, chromium, and lead; and others such as arsenics, fluoride, micro-organisms, radium, sulfate, calcium, magnesium, potassium, nitrate, and phosphorous and hundreds of other contaminants. Thus not making it an ideal option for drinking water needs. This is where Reverse Osmosis shines / comes into play. That said, Reverse Osmosis being one of the appliances that typically gets installed down stream i.e. after water softener, having water softener could protect Reverse Osmosis unity from scales and may extend the longevity of the Reverse Osmosis system. It is not a hard requirement that you have to have water softener for installing Reverse Osmosis system.


They are designed to work independently or together knowing that a residence may or may not have a water softener. There are many Reverse Osmosis systems that remove up to 99.9% contaminants by providing filtered drinking water. Unlike, Brita / Fridge filters, Reverse Osmosis removes Total Dissolved Solids (TDS) in water. In an ideal state, H2O should contain ZERO TDS. However, in real life, a reverse osmosis system, producing water measuring anything less than 50 TDS is really pretty good for drinking water. Just to get an idea, Kirkland water bottles sold by Costco typically have reading around 35 TDS. But many Reverse osmosis systems produce much cleaner water than that i.e. with less than 35 TDS.


Before understanding what a Reverse Osmosis is and how it works, let us first try and understand what an Osmosis is: An Osmosis is a process where a liquid (e.g. water) passes through semi permeable membrane which allows only some molecules such as water (H2o) to pass through it while restricting the passage of salts and other molecules. However, it is it natural tendency of the liquid to move from less concentrated solution (e.g. fresh water) towards more concentrated side (water with salts and other molecules) to even out the concentration. However, when the direction of the flow during the osmosis process is reversed i.e., concentrated water passing through the permeable membrane towards the less concentrated (fresh water) side, it is called reverse osmosis.


At the core, many Reverse Osmosis systems have many permeable membranes commonly called as sediment filter, carbon filter, membrane, UV filter, re-mineralization & pH balance filters. Depending on a particular make and model, you many find some or all of them via which water gets filtered. Any filter is better than no filter :-) That said, when selecting a Reverse Osmosis system, look for NSF certified Reverse Osmosis with common filter sizes. Avoid buying Reverse Osmosis systems that come with proprietary filter sizes or filters not sold in open market as that could result in lot of spend on filters over years and also may cause dependency on person who installed the Reverse Osmosis system for you.


One question that gets asked often is, when do I change my Reverse Osmosis filers? or how do I know when to change filters? While most manufacturer's recommend changing filters every 6 months and membrane every 2-3 years, the best way, I think is to buy a TDS device and to check the TDS reading. If it shows TDS less than 50, normally you are fine and you could wait little longer to change the filters. I always follow this approach as it is more scientific rather than blindly changing by date recommended by manufacturer. Reverse Osmosis system is one of the cost effective (Costco sells couple of good brands with remineralization and pH balance around $200 price point) ways to obtain quality drinking water. If you are handy enough, these systems are pretty easy to install by yourself (typically under kitchen sink) and easy to maintain i.e. checking TDS reading to decided whether or not to change filters, for any leaks at the connections replacing them with john guest connects (most of RO units use these fittings) and re-pressurizing tank when necessary. Hope this helps someone out here. Have a wonderful rest of the day!