Reverse osmosis is usually a small system under the kitchen sink. A whole-house system does the same thing for every tap at once, which makes it a different kind of project: a room’s worth of equipment, its own power and drains, and a price in the thousands.
How it works
A whole-house system works in five stages:
- Pre-treatment filters out sediment, and often softens the water and removes chlorine, so scale and chlorine don’t ruin the membranes.
- The membranes hold back most dissolved minerals and contaminants as a pump pushes water through them.
- The concentrate, the water carrying what the membranes held back, goes down the drain or partly back through.
- A storage tank collects the treated water, because the membranes make it slowly. Tanks can hold well over 100 gallons.
- A delivery pump repressurizes the stored water and sends it to every tap.
That’s why these systems are rated in gallons per day rather than gallons per minute: the membranes fill the tank over the day, and the pump meets your peak demand from it.
What they sell for
Store prices, read on November 4, 2026. The ranges span production capacity and options such as storage tanks.
Whole-house reverse osmosis prices
Sellers’ own prices, read Nov 2026
- US Water Systems · Falcon whole house reverse osmosis$6,795 to $8,416
500 to 2,000 gallons per day, with or without a storage tank
- iSpring · WRO4000 whole house reverse osmosis$9,000
up to 4,000 gallons per day, pump and buffer tank built in
- US Water Systems · Defender whole house reverse osmosis$9,695 to $16,695
4,000 to 8,000 gallons per day, by tanks and options
| Brand | Price | System | Store link |
|---|---|---|---|
| US Water Systems | $6,795 to $8,416on sale | Falcon whole house reverse osmosis500 to 2,000 gallons per day, with or without a storage tank | Check price |
| iSpring | $9,000 | WRO4000 whole house reverse osmosisup to 4,000 gallons per day, pump and buffer tank built in | Check price |
| US Water Systems | $9,695 to $16,695on sale | Defender whole house reverse osmosis4,000 to 8,000 gallons per day, by tanks and options | Check price |
Prices as each seller listed them on November 4, 2026; "on sale" means a discount from a higher list price. We may earn a commission from these links.
Pre-treatment equipment and installation can add to that, depending on your water and the system.
What it takes, in the sellers’ words
US Water Systems publishes the requirements for its Defender system, which give a sense of the project:
- Pre-treatment. On city water, it says hardness treatment, chemical removal and sediment filtration “must be used.” On well water, it requires a lab test first.
- Flow and pressure. At least 10 gallons per minute at 40 PSI coming in.
- Drains. Two air-gapped drain connections that can each handle at least 3 gallons per minute.
- Power. A 220-volt circuit plus two 110-volt connections; it suggests confirming with an electrician.
- Space. At least 72 inches wide by 30 inches deep, with access to the front and sides.
- Plumbing. It says RO water “can be aggressive to soft metals like brass and copper,” while plastic plumbing is unaffected.
iSpring’s WRO4000 takes a different approach: a single rolling unit with its pump and buffer tank built in, which iSpring says delivers 4 gallons per minute at 60 to 80 PSI.
How much water goes down the drain
Every RO system sends part of its water to the drain. Sellers state it as a recovery rate (the share that comes out as treated water) or a pure-to-drain ratio:
- US Water Systems lists standard recovery of 41% and 58% for its two Falcon sizes, and up to 75% when some of the concentrate is recycled. At 58%, about 42 of every 100 gallons go down the drain.
- iSpring describes the WRO4000 as 2:1 pure to drain, which works out to about one gallon down the drain for every two treated.
For a whole house, that adds up. It’s worth asking the seller what recovery to expect on your water, and what it does to your water bill.
The smaller alternative
The common alternative is a small RO system at the kitchen tap, with the rest of the house handled by a whole-house filter, a softener or both. Under-sink RO systems list from $230 in the stores we read; see our under-sink guide. Whole-house RO makes the most sense where the water has problems those can’t handle at every tap, and its sellers ask for a water test before they size one. If you’re on a well, start with testing.
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Questions
How much does a whole-house reverse osmosis system cost?
Store prices we read run from $6,795 (US Water Systems Falcon, smallest size) to $16,695 (US Water Systems Defender with storage and options). That’s before any pre-treatment you need and installation.
How much water does whole-house RO waste?
It depends on the system and your water. US Water Systems lists standard recovery rates of 41% and 58% for its Falcon models, up to 75% with concentrate recycling; at 58%, about 42 of every 100 gallons go to the drain. iSpring describes its WRO4000 as 2:1 pure to drain.
Do I need whole-house reverse osmosis?
Only if a water test shows problems the usual filters and softeners can’t handle across every tap. Reverse osmosis’s extra removal matters most for the water you drink and cook with, which an under-sink reverse osmosis (RO) system covers for a few hundred dollars. Sellers of whole-house RO ask for a water test before they size one.
Can whole-house RO water damage pipes?
US Water Systems says reverse osmosis (RO) water can be aggressive to soft metals like brass and copper, while plastic plumbing is unaffected. The World Health Organization notes that very soft water can corrode pipes. Ask the seller how its system handles that, for example by adding minerals back.