A whole house reverse osmosis system puts an RO membrane on the water line where it enters the building, so every tap gets treated water. RO makes water slowly, so a home system is never just a membrane. It is a package: pretreatment, the RO unit, a storage tank and a pump to push the water through the house. Whether you need one depends on your water. Many homes are better served by a softener plus a small RO unit at the kitchen sink, and this page explains how to tell the difference.
How a whole house RO system works
Each stage protects the next one. Skip one and the membrane pays for it.
| Stage | What it does | Why the system needs it |
|---|---|---|
| Sediment filter | Catches sand, rust and silt | Particles foul the membrane surface. See sediment filters. |
| Carbon filter | Removes chlorine and chloramine from city water | The membrane tolerates under 0.1 ppm free chlorine, and oxidation damage is not covered by the manufacturer’s warranty (DuPont FilmTec data sheet). |
| Softener or antiscalant | Handles calcium and magnesium | Hardness scales the membrane. In Utah this stage is not optional, see below. |
| RO membrane | Rejects dissolved solids and reduces nitrate, arsenic and more | This is the part that lowers TDS. A share of the feed water goes to drain. See RO reject water and recovery. |
| Storage tank | Holds treated water | The membrane produces at a steady, slow rate. The tank covers morning showers and laundry day. |
| Delivery pump | Sends water from the tank through the house at normal pressure | Without it the taps run weak. See booster and delivery pumps. |
| Remineralization | Adds back some minerals and lifts pH | RO water is low in minerals and slightly acidic, which raises the risk of corrosion in plumbing. Neutralizing is the usual fix. |
Homes on a private well often add UV disinfection after the tank, and iron or manganese removal ahead of the membrane. Test first, then design. How to test your home water quality covers the options.
How to size one
Start with real use. The EPA says the average American family uses more than 300 gallons of water per day at home, and roughly 70 percent of that happens indoors. That puts indoor use near 210 gallons a day for an average household. Irrigation does not need RO water, so a good design sends outdoor taps around the system.
Then look at flow, because a membrane does not deliver on demand. Divide the daily output by 1,440 minutes and you get the steady flow the unit can sustain:
| Unit output | Steady flow (gallons per minute) | Example |
|---|---|---|
| 300 GPD | 0.21 | About the size of a household’s average daily use. Too small to cover a home with any margin. |
| 800 GPD | 0.56 | Commercial RO 800 GPD |
| 1,500 GPD | 1.04 | Commercial turnkey RO 1,500 GPD |
| 3,000 GPD | 2.08 | Commercial turnkey RO 3,000 GPD |
A shower alone can draw more than a 1,500 GPD unit makes in a minute, which is why the tank and pump exist. The tank is sized for your peak hour, and the unit is sized so it can refill the tank overnight with room to spare. Pick an output comfortably above your indoor daily use, then let the tank absorb the peaks.
AMPAC does not sell a boxed “whole house RO” unit. The catalog lists commercial RO systems, storage and delivery pumps, and a home package is specified from those parts for your address. Use the RO system calculators to estimate output and recovery, or ask for a quote and an engineer will size it with you.
When whole house RO makes sense
| Your situation | What usually fits |
|---|---|
| Private well with high TDS or brackish water | Whole house RO is a real option. Test TDS first; what the numbers mean. |
| Well with nitrate, arsenic or PFAS | RO at the kitchen tap covers drinking and cooking. Whole house RO only if you want it everywhere. See nitrate removal and PFAS and RO. |
| City water, hard, no health concern | A softener for the building and an under-sink RO system for drinking water. Compare in RO vs water softener. |
| City water, you mostly dislike chlorine | A whole house carbon filter. See whole house vs under-sink filters. |
| Iron or sulfur smell | Treat that first, ahead of any membrane. See iron in well water. |
Two costs deserve a straight look. Most of what leaves your taps never needs RO quality: toilets, laundry, showers. And RO water is low in minerals. Lenntech lists high corrosion potential as an effect of low-mineralized water and notes that RO acidifies the permeate by about one pH unit. A whole house system should include pH neutralization or remineralization, particularly with copper pipes.
Whole house RO in Utah
Utah water is hard, and hardness is what kills RO membranes early. Weber Basin reports 10 to 18 grains per gallon across Davis and Weber counties, and Salt Lake City’s wells reach 33.4. Above roughly 10 grains, softening or antiscalant dosing goes in ahead of the membrane. Read the local numbers before you size anything:
- Salt Lake City, Davis County and Ogden
- Provo and Orem, and St. George, where the average TDS is above the EPA’s 500 mg/L guideline
- Utah water hardness and TDS by city, with a source link for every figure
Installation and service
AMPAC builds its RO systems at 2262 S 1200 W, Suite #103, Woods Cross, UT 84087, and installs and services systems on site anywhere in Utah. For a quote, send your address, whether you are on city water or a well, a recent water test if you have one, how many people live in the house and how many bathrooms it has. Call (385) 530-1026 or request a quote.
Frequently asked questions
What is a whole house reverse osmosis system?
It is a reverse osmosis unit installed where water enters the building, with pretreatment before it and a storage tank and delivery pump after it. Every tap gets treated water, not just the kitchen sink.
Do I need a softener with a whole house RO system?
Almost always, or an antiscalant feed. Hardness builds scale on the membrane and cuts its life. With Utah water at 10 grains per gallon or more, pretreatment for hardness belongs in the design from the start.
How much water does it waste?
Every RO system sends part of the feed water to drain. The share depends on the design, the feed TDS and the recovery setting. Ask for the recovery rate in writing when you compare quotes, and read RO reject water and recovery rates.
Can it run on well water?
Yes, after you test the water. Wells often need iron or manganese removal ahead of the membrane and UV disinfection after it. The test result decides the design.
Is the water safe to drink straight from the tap?
RO water is safe to drink. It is also low in minerals and slightly acidic, so a whole house system should neutralize or remineralize the water to protect the plumbing.
Why not just use an under-sink RO unit?
For drinking and cooking an under-sink unit does the job at a fraction of the size. Whole house RO earns its cost when the whole supply is the problem, such as brackish well water. See whole house vs under-sink.
Sources
- EPA WaterSense, How We Use Water: average household use and the indoor share
- DuPont FilmTec element data sheet: free chlorine tolerance and the warranty note on oxidation damage
- Lenntech, RO post-treatment: neutralization and remineralization: corrosion potential and permeate pH