# whole house reverse osmosis installation: what it involves

> Whole house RO installs in 2-3 days and costs $3,000-$8,000. See pretreatment, storage tank, repressurization pump, and drain requirements.

Canonical: https://watertreatmentpro.com/whole-house-reverse-osmosis-installation/

Last updated: 2026-11-09

Whole house reverse osmosis installation takes 2-3 days and costs $3,000-$8,000 installed. It is not an under-sink unit scaled up: it needs pretreatment, a storage tank, a repressurization pump, and a drain sized for continuous concentrate flow. That combination is why it is a contractor job.

## What the system is made of

A whole house reverse osmosis system is a point-of-entry treatment train that forces all household water through a membrane, then stores and repressurizes the permeate before distribution. It removes 80-95 percent of dissolved solids across every tap.

The components are: a sediment pre-filter, one or two carbon stages, a booster pump, one or more membrane housings, a storage tank, a repressurization pump, and a pressure switch that starts the pump when the tank drops.

Each part exists because of a constraint. The carbon protects the membrane from chlorine. The booster pump provides the 60-80 psi the membrane needs. The storage tank buffers the mismatch between slow membrane production and fast fixture demand. The repressurization pump restores pressure after storage.

## Pretreatment is not optional

Chlorine destroys thin-film composite membranes. A carbon stage ahead of the membrane is mandatory on municipal water, and it must be sized so contact time is adequate at peak flow.

Hardness scales the membrane. Above 7 grains per gallon, most designers specify a softener ahead of the RO. Iron above 2-3 ppm fouls it. Sediment above 5 microns blinds the feed spacer.

That means the real installation is often a softener, a carbon filter, and an RO skid, in that order. Each upstream device adds $500-$4,500 to the project, which is why the $3,000-$8,000 band assumes some pretreatment already exists.

## Storage and pump sizing

| Component | Typical spec | Cost |
|---|---|---|
| Sediment and carbon | 20-inch, two stage | $250 - $650 |
| Booster pump | 1/2 - 1 hp | $300 - $700 |
| Membrane housing | 1 - 2 elements | $400 - $1,200 |
| Storage tank | 20 - 80 gallons | $400 - $1,200 |
| Repressurization pump | 1/2 - 3/4 hp | $400 - $900 |
| Controls and pressure switch | Float, solenoid, switch | $200 - $500 |

Storage sizing runs on daily demand and recovery time. A household using 150 gallons per day with a system that produces 100 gallons per day needs at least a day of storage plus a reserve, so 80 gallons is the practical minimum for most homes.

Undersizing storage is the most common design error. The pump short-cycles, the membrane runs constantly, and the concentrate stream never stops.

## The drain, and what it costs to run

At a 3-4:1 waste ratio, 100 gallons of permeate sends 300-400 gallons to the drain. Over a month, that is 9,000-12,000 gallons of concentrate.

On a septic system, that volume matters. A 1,000-gallon septic tank receiving an extra 300-400 gallons per day is being asked to handle a third of a typical household's total flow again. Check with the septic designer before installing.

On metered water, the cost is direct. At $0.005 per gallon combined water and sewer, 10,000 gallons per month is $50, or $600 per year, just for the concentrate. That figure belongs in the payback calculation.

Some systems use a permeate pump or a recycle loop to cut waste, which can bring the ratio toward 1:1 but raises system cost by $200-$500 and adds complexity.

## Installation sequence

1. Test the raw water for hardness, iron, chlorine, TDS, and bacteria.
2. Install pretreatment in order: sediment, carbon, and softener if hardness is high.
3. Set the RO skid on a level pad with clearance for membrane removal.
4. Plumb feed, permeate, and concentrate lines with valves for sampling.
5. Install the storage tank with a float or level switch and the repressurization pump.
6. Wire the booster pump, repressurization pump, and controls to dedicated circuits.
7. Commission the system, flush the membrane, and test permeate TDS against feed TDS.

## When it makes sense

Whole house RO is justified when a single contaminant affects every tap and no smaller device solves it: high nitrate across the house, arsenic, or very high TDS from a brackish well.

It is rarely justified for taste alone. A $500-$1,800 carbon filter handles chlorine and odor at a fraction of the cost. It is also rarely justified for hardness, where a $1,200-$4,500 softener is the correct tool.

The cost comparison is stark: [whole house reverse osmosis cost](https://watertreatmentpro.com/whole-house-reverse-osmosis-cost/) sets the $3,000-$8,000 range against a $300-$900 under-sink unit that treats drinking water only. Most households are better served by point-of-use RO at the kitchen sink plus a softener at the entry.

If a specific contaminant is driving the decision, [what reverse osmosis removes](https://watertreatmentpro.com/what-does-reverse-osmosis-remove/) lists what the membrane actually rejects, and [reverse osmosis system installation](https://watertreatmentpro.com/reverse-osmosis-system-installation/) covers the smaller format.

One more installation reality: a whole-house RO skid needs a service aisle. Membrane housings are 40 inches long on commercial-style units, and pulling an element requires that much clear space in front of the housing. A utility room that fits the skid but not the service clearance turns a 20-minute membrane change into a two-person job with the unit unbolted.

Also plan for the permeate pump's noise and heat. A 3/4 hp repressurization pump in a finished basement is audible through a wall, and a continuously running booster pump adds warmth to a closed room. A insulated mechanical closet solves both for $300-$800 during the build, and considerably more afterward.