In short: RO recovery rate is the share of feed water that becomes usable permeate: recovery = permeate flow ÷ feed flow × 100. Standard undersink RO units typically run 15–25% recovery; whole-house and permeate-pump systems commonly reach 50–75%. Enter your own feed and permeate flow above for your system's actual number.
This is a planning estimate from your measured flows. Actual achievable recovery is also capped by your feedwater's hardness and silica content and your membrane manufacturer's rated limits — check those before changing your system's recovery or reject ratio.
How recovery rate is calculated
Reverse osmosis splits incoming feed water into two streams: permeate (the treated product water that passes through the membrane) and concentrate, or reject, water (the leftover stream carrying the minerals and contaminants the membrane blocked). Recovery rate is simply the fraction of the feed that ends up as permeate:
recovery % = (permeate flow ÷ feed flow) × 100
The rest of the feed leaves as concentrate: concentrate flow = feed flow − permeate flow. Concentration factor — roughly how much more concentrated the reject stream's dissolved solids are than the feed, assuming the membrane rejects essentially all of them — is 1 ÷ (1 − recovery fraction).
Worked example. A whole-house RO system pulling 8 GPM of feed water and producing 5 GPM of permeate has a recovery rate of 5 ÷ 8 × 100 = 62.5%. Concentrate flow is 8 − 5 = 3 GPM, and the concentration factor is 1 ÷ (1 − 0.625) = 2.67×.
Typical RO recovery by system type
Recovery is a design choice, not a fixed property of "reverse osmosis" — it depends on the system's plumbing, whether it recirculates concentrate, and how many membrane elements or stages it uses.
| System type | Typical recovery | Notes |
|---|---|---|
| Undersink RO, standard | 15–25% | No permeate pump; simplest, highest reject ratio |
| Undersink RO, w/ permeate pump | 50–80% | Reject pressure drives extra permeate through |
| Whole-house / point-of-entry RO | 50–75% | Often uses a recirculation loop |
| Commercial brackish-water RO | 75–85% | Multi-stage membrane arrays |
| Seawater RO (SWRO) | 35–50% | Limited by high osmotic pressure |
Source: DuPont Water Solutions FilmTec Technical Manual; AWWA Manual M46. Actual limits depend on your specific membrane, feedwater chemistry, and antiscalant use.
Worked examples
Undersink RO
20%
Feed 1.0 GPM, permeate 0.2 GPM. Concentrate 0.8 GPM; concentration factor 1.25×.
Whole-house RO
62.5%
Feed 8 GPM, permeate 5 GPM. Concentrate 3 GPM; concentration factor 2.67×.
Commercial brackish RO
80%
Feed 50 GPM, permeate 40 GPM. Concentrate 10 GPM; concentration factor 5×.
What else affects the result
Feedwater hardness and silica. These are what ultimately cap recovery — as more feed becomes permeate, the minerals left behind concentrate in a shrinking reject stream. Once a mineral's solubility limit is exceeded, it precipitates as scale on the membrane. Hard or high-silica water needs a lower recovery target, an antiscalant, or pre-treatment such as softening. See the Langelier Saturation Index calculator to check scaling tendency.
Membrane fouling and age. As membranes foul or degrade, measured permeate flow at a given pressure drops even if the system is still set to the same theoretical recovery, so your calculated recovery can fall over time without any setting changing.
Temperature and pressure. Colder feedwater reduces permeate flux at a given pressure, which can temporarily lower measured recovery; manufacturers publish correction factors for this. Confirm your system is sized correctly with the RO sizing calculator.
Recovery vs. rejection. Recovery is a flow split; it says nothing about water quality. A system can recover a lot of water while still passing more dissolved solids than you'd like. Check contaminant removal separately with the RO rejection rate calculator.
Frequently asked questions
What is a good RO recovery rate?
It depends on the system. Standard undersink RO units without a permeate pump typically run 15–25% recovery. Undersink units with a permeate pump, and most whole-house RO systems, run 50–75%. Commercial brackish-water systems often reach 75–85%. Higher isn't automatically better — recovery is capped by feedwater hardness, silica, and scaling risk on the concentrate side.
How is RO recovery rate calculated?
Recovery rate is the permeate (product water) flow divided by the feed flow, times 100: recovery % = (permeate flow ÷ feed flow) × 100. The remainder of the feed leaves as concentrate, or reject, flow: concentrate = feed − permeate.
Can I increase my RO system's recovery rate?
Sometimes, with a permeate pump, a recirculation loop, or a larger/second-stage membrane array, but recovery is ultimately limited by feedwater chemistry. Pushing recovery too high concentrates hardness, silica, and other scale-forming minerals beyond their solubility limit on the reject side, which fouls the membrane. Any increase should stay within the manufacturer's rated recovery and, for hard or high-silica water, use an antiscalant.
What's the difference between recovery rate and rejection rate?
Recovery rate is about flow: what share of the feed water becomes usable permeate. Rejection rate is about water quality: what share of dissolved solids the membrane blocks from passing into the permeate. A system can have high recovery and low rejection, or vice versa — they measure different things. Use the RO rejection rate calculator for the quality side.
Why does higher recovery increase scaling risk?
As recovery rises, the same dissolved minerals in the feed get concentrated into a smaller and smaller concentrate stream. At 75% recovery the concentrate carries roughly four times the feed's mineral concentration; at 90% recovery it's about ten times. Once that concentration exceeds a mineral's solubility limit, it precipitates onto the membrane as scale.
What if my permeate flow reading is higher than my feed flow reading?
That's not physically possible for a single RO pass and usually means one of the two flows was measured or converted incorrectly — check that both are in the same units and that the feed reading was taken before, not after, the concentrate line splits off.
Sources & references
- American Water Works Association (AWWA). Manual M46: Reverse Osmosis and Nanofiltration.
- DuPont Water Solutions. FilmTec Reverse Osmosis Membranes Technical Manual.
- U.S. Environmental Protection Agency (EPA). Point-of-Use/Point-of-Entry Treatment for Small Drinking Water Systems.
Sarah Bennett, MS
Water Quality & Sustainability Specialist · Portland, Oregon
Environmental scientist (MS, Water Resources) with 9+ years in residential water quality, treatment, and usage efficiency, and 150+ completed assessments. Sarah writes and reviews the treatment, usage, and cost calculators on watercalculator.us. Read full bio
MS Environmental Science, Water Resources (2018) · BS Environmental Engineering (2016)