The search for better water filtration methods has yielded some exciting options over the years. One of the most aggressive and intriguing methods is reverse osmosis. Here is a look at what reverse osmosis is and why your water filtration system could benefit from it.
Definition of Reverse Osmosis
Osmosis refers to the natural tendency of all dissolved materials in all fluids to go from areas of higher concentration to areas of lower concentration. If you’ve ever squirted food coloring dye into water and watched the cloud spread out, then you have observed osmosis in action.
What happens if we want to go from low concentrations to higher ones, though? For example, forcing pure water out of a solution with lots of debris, undesirable chemicals, and pathogens is one of the main goals of water purification. The water doesn’t naturally do this, but we can force it.
Reverse osmosis involves using water pressure to push a solution through extremely fine pores. Measuring just 0.0001 microns, the pores in the membranes used for typical reverse osmosis are tinier than virtually anything that’s suspended in the water. At this scale, even bacteria and viruses are far too large to pass through. Even most of the smallest chemicals and dissolved solids won’t pass through at a molecular scale. What you get is almost entirely water.
Filtration Stages
To maximize the efficiency of reverse osmosis filters and to minimize the need to replace membranes constantly, the modern version of the process has three stages. Pre-filtration is an initial process to capture large particles and debris that might otherwise clog the membrane’s pores. Likewise, the pre-filter removes chlorine that could react with and damage the membrane.
The second stage is the membrane stage. This uses high pressures, up to 100 pounds per square inch for residential applications. Cross flows ensure that the membrane doesn’t foul due to collecting materials from the same direction constantly. Likewise, a concentrate is used to clear out the rejected contaminants, once more to keep the pores open.
The final stage is post-filtration. Multiple filters may be useful at this stage. Carbon filters can remove harmless smells and tastes using activated carbon to react with certain chemicals. UV sterilization is also an option for ensuring maximum disinfection. Some people like to remineralize the water with beneficial minerals at this stage, too. Especially if you find the taste of extremely pure water to be off-putting, you may want to consider including remineralization with your reverse osmosis filter.
Reverse Osmosis Effectiveness
Reverse osmosis is highly effective at removing total dissolved solids. These are things like salts, metals, and minerals that often negatively affect water quality. Unsurprisingly, reverse osmosis works extremely well at removing heavy metals like lead, arsenic, and mercury. In all these cases, you can expect 95 to 99 percent effectiveness.
Removal of microorganisms is extremely effective. Reverse osmosis will remove more than 99.9 percent of bacteria, viruses, mold spores, and other potential pathogens.
Notably, reverse osmosis is only moderately effective at removing many chemicals. You can expect it to get rid of 85 to 95 percent of nitrates. Likewise, RO is effective at removing about 60 to 90 percent of volatile organic compounds. Fortunately, many additional methods are good at reacting with these chemicals to clear them from your water. Reverse osmosis is highly ineffective at removing chlorine. That is why pre-filtration is necessary.
Acidity
Reverse osmosis does tend to leave treated water slightly acidic. Most people will not notice the difference, but some report treated water as having a slightly metallic taste. It is possible to neutralize the acidity. This may be desirable if treated water upsets your stomach or tastes off. Also, acidic water can corrode some types of metal pipes and fixtures.
Several post-filtration methods manage acidity. Adding calcium carbonate, the same product used in many over-the-counter antacids, is an option. Alkaline filters can also bring the pH of the water closer to neutral. It is best to test whether the acidity level bothers you before taking the step of treating it.
Usable Water Capacity
Typical reverse osmosis systems in residential settings provide about 50 to 150 gallons of drinkable and highly purified water. Many households specifically split their water filtration to focus on reverse osmosis for drinking needs. They use less filtered water for dishwashers, showering and bathing, and washing clothes.
Energy Consumption
The reverse osmosis filtration process requires electricity to power the pressure that drives the water through the membranes. The typical power consumption for this process ranges between three and ten kWh per 1,000 gallons. High-efficiency models are available that tend toward the three kWh mark, but most modern systems hover around six kWh. The ten kWh figure mostly covers older systems.
Water Waste
Most residential RO solutions aren’t particularly efficient in terms of water consumption. To produce one gallon of water using a standard RO setup, you can expect three to four gallons to end up flushed out with undesirable contaminants. Some newer high-efficiency designs have that down to one or two gallons of waste per purified gallon.
Maintenance Needs
The pre- and post-filtration systems for reverse osmosis need replacement once every six to twelve months. Membranes usually hold up for about three years between replacements. The overall maintenance cost per year averages out to a couple of hundred dollars per year for most residential systems.
Upfront Costs
The aggressiveness of filtration significantly affects the upfront cost of a reverse osmosis system. However, most designs cost between a few hundred to a few thousand dollars. Installation is an additional cost, with more complex routing requiring additional attention. Our plumbers can separate lines to minimize the misuse of drinking- and food-grade water.
Trends to Watch
Efficiency is one of the major targets for improvement in reverse osmosis. Companies continue to work on solutions that employ less water, clearing out undesired compounds. Likewise, research continues to yield setups that use less water pressure, with some newer systems only employing 35 PSI.
Smart systems are becoming popular throughout the plumbing industry, and reverse osmosis is no exception. Connected systems monitor water pressure and warn of leaks. They can also track how well the concentration of unwanted minerals is clearing out, providing a heads-up for maintenance tasks like replacing filters and membranes.
Work with the Best Plumbing Company in San Jose
Plumbtree Plumbing & Rooter serves San Jose, CA and Silicon Valley. We are available 27/7 and every day of the year. Our business is locally based and family-operated. We are BBB-accredited, Diamond Certified, Top-Rated on HomeAdvisor, and a Yelp Nextdoor Neighborhood Favorite.
In addition to water filtration options, our plumbers install, repair, and maintain various plumbing systems and fixtures. Our plumbers are fully licensed. We offer financing upon approval for many plumbing installation projects. Check our website’s specials page for our current deals, too, or to learn more about your options.
Reach out to Plumbtree Plumbing & Rooter now to learn whether reverse osmosis or another water service is right for your San Jose household.
