How Much Water Does an RO Purifier Waste? (India 2026)
Reverse-osmosis purifiers clean water by pushing it through a membrane — and most of the water doesn't make it through. A typical domestic RO recovers only about 25% of what it takes in, sending roughly 3 litres to the drain for every 1 litre you drink. We worked out what that means in real litres — per litre, per month and per year for a household — how much an efficient unit saves, and how to put the reject water to use instead of wasting it.
Last updated: 12 August 2026Sources: RO recovery-ratio range, input-TDS dependence, BIS drinking-water guidance
In short: a typical domestic RO recovers ~25% of the water, so it wastes about 3 litres per 1 litre purified. A family purifying ~10 litres a day pours away about 30 L/day — roughly 900 L a month and ~10,950 L a year, about a 10,000-litre water tanker. An efficient 50%-recoveryRO roughly halves that, and new BIS-compliant units (targeting ~60%) waste less still. And the reject water isn't sewage — it's just high-TDS, so you can reuse it for mopping, flushing and washing (never for drinking or salt-sensitive plants).
Key Numbers at a Glance
~3 L
Wasted per 1 litre purified (typical 25%-recovery RO)
reject = 1/recovery − 1
~900 L/mo
Wasted by a 10 L/day household (25% recovery)
~30 L/day to the drain
~10,950 L/yr
Per household — about a 10,000-litre tanker
poured down the drain annually
~50%
Recovery of an efficient RO — roughly halves the waste
new BIS-compliant units target ≥60%
reuse it
Reject water is high-TDS, not sewage — fine for mopping / flushing
not for drinking or salt-sensitive plants
TDS↑ = waste↑
Higher input TDS lowers recovery and raises waste
membrane works harder
Use this data
The full table as a CSV — reject water per litre and per household by RO recovery ratio and usage. Free to reuse with attribution (CC BY 4.0).
How to cite: PakkaPick, “How Much Water Does an RO Waste? (India 2026),” pakkapick.in/ro-water-wastage-india-2026 — CC BY 4.0
RO forces water through a fine membrane that blocks dissolved salts. The salts have to go somewhere, so they leave in a concentrated “reject” stream that goes to the drain. The fraction that makes it through as clean water is the recovery ratio:
reject water per litre purified = (1 ÷ recovery ratio) − 1
25% recovery → 3 L wasted · 33% → 2 L · 50% → 1 L, per litre you drink
Recovery ranges widely: many older and installed units manage only ~20–25% (3–4 L wasted per litre), while newer units reach 50% and BIS-compliant models target ~60%+. Higher input TDS (hard borewell water) lowers recovery, so the same purifier wastes more where the water is harder.
The rules are tightening. India's Water Purification System (Regulation of Use) Rules, 2023 (in force Nov 2024) and the BIS standard IS 16240:2023push domestic RO toward higher recovery (around 60%+, i.e. under ~0.7 L wasted per litre) and discourage RO where the source is already low-TDS (below ~500 mg/L), where it mostly strips useful minerals and wastes water for little benefit. So the “3 litres wasted” figure describes the large installed base of older units — a new, compliant unit should waste far less.
How much a household actually wastes
For a family purifying ~10 litres a day (drinking + cooking), here is the reject water by RO efficiency — the difference between a basic and an efficient unit is thousands of litres a year.
Water wasted by a 10 L/day household by RO recovery ratio.
RO recovery
Wasted per 1 L
L/day
L/month
L/year
~25% (1:3) — many older / installed units
3.0 L
30
900
10,950
~33% (1:2) — mid-range unit
2.0 L
20
609
7,411
~50% (1:1) — efficient / “low-waste” RO
1.0 L
10
300
3,650
~60% (1:0.7) — new BIS-compliant target (IS 16240:2023)
0.7 L
7
200
2,433
Assumes 10 L/day purified for a family of four. Scale to your own use: waste is directly proportional to how much purified water you draw.
By household size, on a typical 25%-recovery RO:
Water wasted per year by daily purified usage at 25% recovery.
Purified use
Wasted L/day
Wasted L/month
Wasted L/year
7 L/day
21
630
7,665
10 L/day
30
900
10,950
15 L/day
45
1,350
16,425
At ~25% recovery, three litres go to the drain for every litre used. An efficient 50%-recovery unit halves every number in this table.
Don't waste it — reuse the reject water
Fine to reuse for
Mopping floors, flushing toilets, washing utensils, cars and bikes, and general cleaning. Collect the reject line in a bucket or route it to an overhead tank. It's just higher in dissolved salts, not dirty water — though too hard for laundry, where the salts waste detergent.
Avoid using it for
Drinking or cooking (that's the whole point of the RO), and regular watering of salt-sensitive plants or garden soil — the higher salt content can harm them over time. Very hard reject water may also leave scale on surfaces.
Cut the waste at source: pick a higher-recovery (50%+) RO, keep the membrane and pre-filters serviced, and only run RO if your input TDS actually needs it — low-TDS municipal water often doesn't. See RO vs UV vs UF to check whether RO is even right for your water.
Frequently Asked Questions
How much water does an RO purifier waste?
Many older and installed domestic reverse-osmosis (RO) purifiers recover only about 25% of the water they take in — so they send roughly 3 litres to the drain for every 1 litre of purified water. More efficient and newer units recover 50–60%+, wasting about 1 litre or less per litre; India’s 2023 rules (IS 16240:2023, in force Nov 2024) push new units toward that higher recovery. The exact figure depends on the membrane, water pressure and, above all, your input water’s TDS: harder, higher-TDS water pushes recovery down and waste up.
How much water does my household waste through the RO in a year?
Take your daily purified use and multiply by the reject ratio. A family that purifies about 10 litres a day for drinking and cooking, on a typical 25%-recovery RO, wastes about 30 litres a day — roughly 900 litres a month and about 10,950 litres a year. That is close to a 10,000-litre water tanker (or two smaller 5,000-litre tankers) poured down the drain annually, per household. An efficient 50%-recovery unit roughly halves it to ~5,475 litres a year.
Can I reuse RO reject/waste water?
Yes — the reject water is simply higher in dissolved salts (TDS), not sewage, so it is fine for non-drinking uses: mopping floors, flushing toilets, washing utensils or a vehicle, pre-rinsing, and cleaning. Collect it in a bucket or plumb it to an overhead tank. Two cautions: do not drink it, and avoid using it on salt-sensitive plants or in regular quantities on garden soil, because the higher salt content can harm them over time. Very hard reject water can also leave scale on surfaces.
Do I even need an RO for my water?
Only if your supply is genuinely high-TDS. RO is designed to remove dissolved salts, so it makes sense mainly where input TDS is high (roughly above 300–500 ppm, common with borewell/groundwater). If your municipal supply is already low-TDS (often below ~200 ppm), an RO can strip useful minerals and waste water for little benefit — a UV or UF purifier may suit better, and India’s 2023 rules in fact discourage RO below ~500 ppm TDS. One caveat: if low-TDS water still carries a dissolved chemical like fluoride, arsenic or nitrate, UV/UF cannot remove it and RO is still the right tool. Check your input TDS (and any known contaminants) before assuming you need RO.
How can I reduce RO water wastage?
Four practical levers: (1) buy a higher-recovery RO (50%+ recovery, sometimes marketed as “low-waste” or with a reject-recirculation pump); (2) route the reject line into a storage bucket or overhead tank and reuse it for cleaning and flushing; (3) keep the membrane and pre-filters serviced — a clogged system wastes more; and (4) only run RO if your input TDS actually needs it. Together these can cut a household’s RO water waste by more than half.
Sources & Methodology
Reject water per litre purified = (1 ÷ recovery ratio) − 1; household waste = that ratio × your daily purified use. We use ~25% recovery as the typical domestic case and 50% as an efficient unit, with the honest range of ~20–50%.
RO recovery ratio — the permeate-to-feed fraction of a reverse-osmosis system; domestic units typically ~20–50%, dependent on membrane, pressure and input TDS.
Input-TDS dependence — higher feed-water TDS (hard/borewell water) lowers recovery and raises reject volume for the same purifier.
BIS drinking-water guidance (IS 10500) — context on when RO-level treatment is warranted vs UV/UF for lower-TDS supplies.
Water Purification System (Regulation of Use) Rules, 2023 + IS 16240:2023 — in force Nov 2024; push domestic RO toward ~60%+ recovery and restrict RO where source TDS is below ~500 mg/L.
Figures are estimates for guidance: your actual waste depends on your specific purifier's recovery, water pressure, input TDS and how much water you draw. This page contains no product prices.
Related guides
Choosing, running and maintaining a water purifier for Indian water.