If you are wondering how to purify water in your home, you’re probably overwhelmed at the options. There are whole house systems, filters that you attach to your faucet, and filter systems that install under the sink. Carbon filters, softeners, ozone machines and reverse osmosis systems all claim to purify the water. Manufacturers of reverse osmosis systems claim they are the best. But, are reverse osmosis water systems really good? Let’s see.
How Reverse Osmosis Water Systems Work
In nature, osmosis describes how a less concentrated fluid will naturally flow through a semi-permeable membrane into a more concentrated fluid until the concentration levels on both sides of the membrane are equal. It occurs naturally and requires no energy. It’s how water moves through our body, and in the body, water is the only liquid that can pass through the membrane. That’s why the membrane is called semi-permeable
Reverse osmosis applies pressure so that the more concentrated solution is pushed through the semi-permeable membrane into the less concentrated solution. For the purposes of water purification, the semi-permeable membrane only allows the passage of water, hence the term semi-permeable name.
Because the semi-permeable membrane only allows water through, reverse osmosis water systems are really good at cleaning impurities from water.
But, they do have their limitations. The reverse osmosis process creates reject water. Not all water that goes into the system comes out. It takes about four gallons of feed water to produce one gallon of pure water. The membranes must be cleaned, or they will become covered with a plaque that keeps them from working. Most importantly, the quality of the water coming out depends on the quality of the membrane.
The Membrane is the Heart of the System
What makes reverse osmosis water systems really good is the membrane. The quality of the membrane determines the quality of the water from the reverse osmosis process. Reverse osmosis membranes are subject to degradation by oxidizing pollutants such as iron and manganese. Hardness (the amount of calcium and magnesium in the water) can also lead to early membrane failure. pH of the water is a factor as well.
Reverse osmosis filters are like any filter and clog over time. In order to clean the filter, you must backwash the filter (just like a pool filter). Backwashing pushes water backwards through the membrane. This loosens any particles clinging to the membrane and washes them away. The best reverse osmosis systems backwash automatically. Other systems have a valve that you must turn to manually backwash the membrane. The lowest quality reverse osmosis systems have no mechanism in place to backwash the membrane.
The Need for Prefiltering
Because the reverse osmosis membrane is the heart of the system, it needs protection. A high level of turbidity in the feed water clogs the membrane quickly. A sediment prefilter is a good idea in these instances.
Because chlorine can damage reverse osmosis membrane, it is important to remove chlorine from the feed water before it reaches the membrane. Use a prefilter to remove chlorine and it’s not a problem.
Prefiltering isn’t essential to make a reverse osmosis system work. It is essential to keep a reverse osmosis system working for any period of time. That’s why it is common to see some arrangement of sediment and carbon filters installed as prefilters before a reverse osmosis membrane. Prefilters are like an insurance policy to protect the membrane.
The Verdict? Reverse Osmosis Systems ARE Really Good
If you need the cleanest drinking water possible, reverse osmosis systems are really good if they have a really good membrane.
That’s because they remove all forms of contaminants. That includes heavy metals, inorganic solids, chemicals, and biologics like bacteria and cysts.
While they do produce a significant amount of waste water, the clean water they produce is genuinely clean. That’s excellent for drinking water and cooking water.
Are reverse osmosis water systems really good? They are the best!