Whole Home Osmosis: Everything You Need To Know

Reverse osmosis produces water of remarkable purity by separating chemicals, pesticides, pharmaceuticals, and dissolved solids from the water. While rarely used as a whole house water filtration system, some groundwater is so severely contaminated that reverse osmosis is the only viable option for providing the home with clean water. A whole house reverse osmosis system requires careful planning, diligent maintenance, and a researched understanding of your water’s chemistry. Whole house reverse osmosis systems can be complex endeavors. Still, they can also restore water quality to homes affected by astronomical levels of TDS or dangerous quantities of contaminants like hexavalent chromium.


A whole house reverse osmosis system is a water filtration system that filters the entirety of your home’s water through a reverse osmosis membrane. A whole house reverse osmosis system is installed at the point where water enters your home. Every drop of water entering your household plumbing is treated by the reverse osmosis membrane, from your drinking water at your kitchen sink to the water you use to shave, shower, and flush your toilets. Whole house reverse osmosis (RO) systems ensure that your entire home is free from any traces of water hardness, salts, chemicals, and TDS. The microscopic pores on the semipermeable membrane of the RO system can eliminate over 98% of dissolved organic and inorganic matter. The water produced by reverse osmosis is almost unparalleled in its purity, and it is a more cost-effective method of purification than deionization or distillation. While reverse osmosis is commonly used for residential point-of-use drinking water, those with extremely challenging water conditions install a whole house RO system to provide exceptional water quality throughout their home. 

Reverse osmosis removes a host of contaminants, like chromium, uranium, copper, mercury, arsenic, boron, silver, lead, sodium, and nitrates. Many of these can pose health risks in elevated quantities, and there are limited filtration methods effective at eliminating these all at once. While an under-sink RO system is ideal for providing purified water at a single faucet, sometimes water presents challenges that can affect your whole home. If toxic levels of chemicals and metals compromise your water source, it can be wise to eliminate these from every faucet in your home. In addition, there are some cases where the water you brush your teeth with, bathe your children in, and use to cook and clean should all be purified by reverse osmosis.  


A whole house reverse osmosis system is only necessary for specific water problems. There are very few water quality issues that are so severe that they can only be addressed by whole house reverse osmosis. Whole house reverse osmosis will most commonly be found in rural homes on wells, where numerous difficult contaminants compromise the groundwater. Water with high levels of naturally occurring compounds like arsenic and nitrates can only be treated by reverse osmosis.  Homes built near manufacturing plants may see elevated levels of microplastics, volatile organic compounds like benzene, chemicals like PFAS, or high concentrations of dissolved salts. Removing these contaminants poses a unique challenge that few water filtration systems are equipped to tackle. When these contaminants emerge in unison, they can be especially troublesome, and reverse osmosis is sometimes the most viable way to eliminate them from the water. If you live with water with exceptionally elevated levels of TDS, you may decide you want to protect your entire home from these contaminants by installing a whole house RO system. 

Municipal water supplies are disinfected by chlorination and are quite unlikely to contain levels of contaminants that could only be addressed by reverse osmosis. Contaminants you may find in city water like water hardness, chlorine, chloramines, and lead can all be treated effectively by other whole house water filtration systems. However, some people on municipal water prefer RO water and want the entirety of their home to use reverse osmosis water. People are also increasingly concerned about the presence of fluoride in municipal water. Unfortunately, fluoride, a naturally occurring mineral, is synthetically added to city water supplies to reduce the risk of tooth decay in children. Fluoride is extremely tough to remove from water. The industry standard for removing it is by using a filtration media called activated alumina, a process that is impractical for most applications. Activated alumina requires a very lengthy contact time with the water to reduce fluoride and produces water at a rate of about 0.25 GPM. Plumbing a whole house with such low water pressure is ultimately unfeasible, so those wanting to remove fluoride from their home entirely usually turn to reverse osmosis. 


The only way to truly know if your water needs to be treated by whole house reverse osmosis is to perform a detailed water test. Many contaminants that pose the biggest threat to your health and home are tasteless, odorless, and colorless. Your well water may be discolored, taste like metal, and bear a harsh odor, but many of these problems are solvable by much simpler filtration systems. A rigorous water test kit will reveal your water’s organic, chemical, and metallic composition, identifying the levels of everything from pesticides and ammonia to arsenic and cyanide. Without a thorough understanding of what is in your water, it is impossible to know how to best go about eliminating the contaminants. A water test will help illuminate what pretreatment your water needs to undergo before it reaches the reverse osmosis system. Without a water test, you will also be unable to gauge the success of your whole house reverse osmosis system. 

If the water test reveals your well has concentrations of nitrates, nitrites, arsenic, chromium, or TDS far above what the EPA has established as safe, you then need to contact a water specialist. While an under-sink reverse osmosis system can be used to restore your drinking water’s taste and safety, there are some applications where you will need a system to service the entirety of your home. 


The best way to test your well water is to collect a water sample from your well and send it to a state or nationally certified laboratory to be tested. Your water samples will then be subjected to the same water quality tests used to ensure the safety of bottled water and municipal water supplies. Water test labs use the EPA standards for safe drinking water to check your well, measuring the presence of contaminants in the parts-per-million. Within two weeks, they will return your report to you, flagging every instance where your water exceeds the EPA’s regulatory standards for safe drinking water. 

Since private wells are unregulated, it is incumbent upon the well owner to test their water and ensure their home’s drinking water is safe. If you are on a well, performing detailed water tests should be an annual part of your diligent well maintenance. Furthermore, if you are considering a whole house reverse osmosis system, it’s necessary to understand exactly what is present in your water to craft an effective strategy for achieving the high-purity water you desire. If you are on municipal water, you have the option of performing a lab test. However, cities are mandated by the EPA to release an annual water quality report. The Environmental Working Group (EWG) maintains an online database of these reports, which are searchable by zip code. 


A whole house reverse osmosis system will cost around $12,000 to $20,000. While the price of a commercial-grade reverse osmosis system is approximately $3,000-$5,000, the pretreatment of the water, the pressure booster pumps, and the installation will all increase the cost. The RO’s filters and membranes require regular replacements, as will the components of your other filtration systems. Water softeners require resin beads and periodic replenishment of salt in the brine tank. UV lamps need to be changed every year, and the quartz sleeves every two years. Carbon and sediment filters usually need to be changed every six months, and your acid neutralizer will dissolve its calcite media over time. 

The cost of whole house reverse osmosis also heavily depends on the size and output of the system. The greater the gallons per day produced by the system, the more expensive the initial cost. A higher output system demands a larger storage tank, which is another expense to factor into the overall cost. Though you can install the system yourself, it is wise to consult a professional plumber or water treatment expert. Whole house RO is complex, and it is vital that all the components must be installed properly. Otherwise, you could see diminished household pressure and flow rates and risk reduced performance from your system. Whole house reverse osmosis is an expensive investment with ongoing costs and regular maintenance. However, it can be a welcome relief from hazardous water quality in situations where it is the only option to purify your water.