What Reverse Osmosis Actually Removes
Reverse osmosis water is exceptionally pure, typically removing 95 to 99 percent of dissolved solids, heavy metals, and common contaminants from tap water. In El dorado hills, California, where municipal and well water can carry minerals, chlorine, and trace contaminants, RO systems deliver some of the cleanest drinking water available at home. I'm Eli, a Certified Water Specialist with over 20 years installing and servicing residential and commercial water treatment systems across the country.
RO works by forcing water through a semipermeable membrane that blocks particles larger than water molecules. What comes out the other side is remarkably clean: fluoride, lead, arsenic, nitrates, chlorine byproducts, and sodium are all reduced to near-undetectable levels. The result is water that tastes neutral, feels light, and leaves almost no residue when it evaporates.
How Pure RO Water Really Gets
Most residential RO systems produce water with total dissolved solids between 5 and 20 parts per million, compared to typical tap water that runs 150 to 400 ppm or higher. That level of reduction is significant. I've tested RO output in hundreds of homes, and when the system is working correctly, the purity is consistent. One thing people don't always realize is that RO doesn't just filter, it separates. The membrane rejects contaminants and flushes them to the drain, which is why RO water stays so clean over time.
In El Dorado Hills, where water hardness and seasonal mineral content can vary, a 5-stage RO system handles those shifts without losing performance. The pre-filters catch sediment and chlorine before they reach the membrane, and the post-filter polishes taste. That layered approach is what keeps the water pure, not just once, but month after month.
What RO Leaves Behind
RO removes so much that some people worry it strips out everything, including beneficial minerals. That's mostly true. Calcium, magnesium, and potassium are reduced along with contaminants. For most families, that's not a health concern because those minerals come primarily from food, not water. But if you prefer mineralized water, you can add a remineralization cartridge after the membrane. It reintroduces a small amount of calcium and magnesium without bringing back the contaminants.
I've installed systems both ways. Some customers want the purest possible water and don't mind the flat taste. Others add the remineralization stage and notice a slightly smoother feel. Neither choice affects safety. The water is still extremely pure either way. What matters more is that the system is sized correctly and maintained on schedule so the membrane stays effective.
Common Misunderstandings About RO Purity
One myth I hear often is that RO water is acidic and harmful. RO water does have a slightly lower pH, usually between 5.5 and 6.5, because it lacks buffering minerals. But that doesn't make it unsafe. Your body regulates pH tightly, and drinking RO water won't change that. What it does do is reduce exposure to contaminants that shouldn't be in drinking water in the first place.
Another misconception is that RO wastes too much water to be worth it. Yes, RO systems send water to the drain during the filtration process, typically three to four gallons of waste per gallon produced. But when you compare that to bottled water waste, both environmental and financial, the trade-off makes sense for most households. In areas like El Dorado Hills, where water quality varies and families want control over what they drink, reverse osmosis systems offer reliable purity without ongoing plastic waste.
When RO Makes the Most Sense
RO is ideal when you want the highest level of contaminant reduction available for home use. If your water test shows lead, arsenic, nitrates, or high TDS, RO addresses all of those at once. It's also the right choice if you're concerned about emerging contaminants like PFAS, which carbon filters alone don't fully remove. I recommend RO systems most often for families with young children, anyone with immune concerns, or homes where the source water quality is inconsistent.
That said, RO isn't always necessary. If your main issue is chlorine taste or sediment, a whole-house carbon filter may be enough. RO works best when installed under the sink for drinking and cooking water, not as a whole-house solution. It's slower and more selective, which is exactly what makes it so effective. For homeowners in El Dorado Hills evaluating their options, I'd suggest testing your water first, then deciding whether RO-level purity is worth the investment. In most cases where contamination or taste is a concern, it is.
If you're ready to explore the right system for your home, start with a quick water assessment to see which filtration approach fits your water quality and household needs.
Frequently Asked Questions
Does reverse osmosis remove all bacteria and viruses?
RO membranes block most bacteria and viruses due to their small pore size, but RO systems are not certified as standalone disinfection devices. If microbial contamination is a concern, pair RO with UV treatment or use municipally disinfected water as the source.
How often should I replace the RO membrane?
Most RO membranes last two to three years with proper pre-filtration and regular filter changes. If your TDS starts creeping up or flow slows significantly, it's time to replace the membrane. Pre-filters should be changed every six to twelve months to protect it.
Can I use RO water for cooking and coffee?
Yes. RO water improves the taste of coffee, tea, and soups by removing chlorine and minerals that can alter flavor. Many people notice a cleaner, more neutral taste when cooking with RO water, especially in El Dorado Hills where mineral content can vary seasonally.
Will RO water damage my appliances?
No. RO water is low in minerals, so it won't cause scale buildup in appliances like coffee makers or steam irons. In fact, it can extend their lifespan by preventing mineral deposits that clog internal components over time.
Is remineralization necessary after reverse osmosis?
Remineralization is optional, not required. RO water is safe to drink as-is. Adding minerals back with a post-filter cartridge can improve taste and slightly raise pH, but it doesn't change the safety or purity of the water.