Reverse osmosis systems for drinking and cooking water
An under-sink unit that treats the water you drink. In central Iowa it is the answer to nitrate and dissolved solids, and it is the cheapest system I install.
How does reverse osmosis work?
Reverse osmosis pushes water under household pressure through a semi-permeable membrane with pores small enough to block dissolved contaminants that a carbon filter passes straight through. Water goes through a sediment pre-filter, then a carbon pre-filter that protects the membrane from chlorine, then the membrane itself, into a small storage tank, and finally through a post-filter on its way to a dedicated faucet.
That sequence is why RO reduces nitrate, total dissolved solids, fluoride, sodium and a long list of dissolved metals, while a pitcher filter or whole-home carbon unit does not. The tradeoff is flow. An RO system makes water slowly and stores up what it makes, so it feeds one tap for drinking and cooking instead of the whole house.
What an RO system reduces, and what it leaves
A residential RO membrane rejects the large majority of dissolved solids. In practice that covers the contaminants central Iowa homeowners ask about most, nitrate first among them. It also strips out the minerals you want, calcium and magnesium, so remineralization is a conversation worth having before the thing goes in.
- Nitrate, which no softener or carbon filter meaningfully touches
- Total dissolved solids, the number behind flat or metallic taste
- Sodium, including the sodium a water softener adds upstream
- Fluoride, lead, arsenic and most dissolved metals
- Chlorine taste and odor, handled by the carbon stages
What it does not do is soften your water. The membrane treats a few gallons a day at one faucet. Hardness is a whole-house problem measured in thousands of grains per day, which is a softener job.
Sizing, remineralization and the drain ratio
Residential systems are rated in gallons per day, and most households are well served between 50 and 100 GPD. The number that matters more in daily use is the storage tank, because that is what determines whether you can fill a stockpot without waiting.
Two options are worth deciding on deliberately instead of taking whatever happens to be on the truck. A remineralization stage adds calcium and magnesium back after the membrane, which restores taste and raises pH for people who find RO water flat. A permeate pump reduces the water sent to drain and improves tank fill, which matters if you are conscious of waste during a watering ban summer.
What maintenance runs you
Pre-filters and post-filters are replaced roughly annually. The membrane itself typically lasts two to five years depending on your incoming water and whether the carbon pre-filter was changed on schedule, which is the single thing that determines membrane life. We write the interval and the cost of consumables into the quote, because a system is only as good as the maintenance you were told about before you bought it.
Why central Iowa households choose RO specifically
Three reasons, in the order people here bring them up. First one is that it works and the alternatives do not. Softeners and carbon filters leave nitrate alone, so after two watering bans in two summers this is the question I field more than any other, and RO is the real answer to it.
The second is cost. An under-sink unit is a fraction of a whole-home installation, which makes it the highest-value place to start for a household worried specifically about what they drink.
The third is scope. You drink and cook with a few gallons a day and wash with the rest. Treating those few gallons thoroughly is a better use of money than treating everything lightly, and it is why we do not try to solve nitrate at the main line.
Questions we get asked
Does reverse osmosis remove nitrate?
Yes. Reverse osmosis is the standard household method for reducing nitrate in drinking and cooking water. The membrane blocks dissolved nitrate that carbon filters and water softeners pass through. That is why RO goes in at the point of use in central Iowa homes instead of trying to treat nitrate for the whole house.
Does RO water taste flat, and can that be fixed?
Some people find it does, because the membrane removes beneficial minerals along with contaminants. A remineralization stage added after the membrane puts calcium and magnesium back and raises the pH, which restores the taste most people expect. Decide on it up front. Retrofitting one in later is a bigger pain than it sounds.
How much water does an RO system send down the drain?
Residential systems send some water to drain as part of flushing the membrane, and the ratio varies by system and by your water pressure. A permeate pump reduces it noticeably and improves how fast the storage tank fills, which is worth specifying in central Iowa given recent summer water restrictions.
How often do the filters need changing?
Pre-filters and post-filters are typically annual. The membrane usually runs two to five years, and its life depends heavily on whether the carbon pre-filter was changed on schedule, since chlorine damages the membrane. We put the intervals and consumable costs in the written quote.
Can you install RO if I already have a water softener?
Yes, and the two work well together. The softener protects your plumbing and appliances from hardness, and the RO unit handles what you drink, including reducing the sodium the softener adds. Many central Iowa homes run exactly this combination.
Get a fixed price on an RO system
We test your tap first, then quote in writing. Most under-sink installations finish in one visit.