Two of the most common appliances in Indian homes and offices — the RO water purifier and the air conditioner — both waste water as a normal part of how they operate. Neither is doing anything wrong; it's just how the technology works by default. The good news is that both waste streams are easy to intercept and reuse, and RO waste water reuse in particular has become a common starting point for households looking to cut waste.
Where RO purifiers waste water
Reverse osmosis purifiers work by forcing water through a membrane that filters out dissolved solids. That membrane can't pass all the incoming water through as purified output — a portion is rejected as concentrate, carrying the filtered-out minerals with it, and by default that reject stream goes straight down the drain. Depending on the system and incoming water hardness, purifiers commonly reject more water than they actually purify, meaning a large share of what goes into the unit never reaches your glass.
Where AC condensate goes
Air conditioners produce condensate as a byproduct of cooling — water pulled out of humid air as it passes over the cold evaporator coil. That water is close to distilled: low in minerals and generally clean. Almost every AC unit routes this condensate straight into a drain line and out of the building, even though it's one of the cleanest waste streams a home or office produces.
What both waste streams are good for
Neither RO reject water nor AC condensate is contaminated — they're simply water with nowhere useful to go by default. Both are well suited to mopping floors, flushing toilets, washing vehicles, and watering outdoor or hardier plants. AC condensate, being nearly mineral-free, is gentler on sensitive potted plants than RO reject water, which carries a higher mineral load and is better suited to general cleaning or hardier greenery.
How to actually capture it
In both cases, the fix follows the same basic idea: intercept the waste line before it reaches the drain and redirect it into a storage container instead. For RO purifiers, that means tapping the reject line rather than the purified-water line. For AC units, it means fitting a diverter onto the existing condensate drain. Neither change affects how the appliance performs — your RO purifier still produces the same quality drinking water, and your AC still cools exactly the same.
The two streams also behave differently day to day, which affects how you'd use the storage. RO reject water flows whenever the purifier runs, in short, frequent bursts tied to how often the household draws drinking water. AC condensate is tied to weather and cooling hours instead, so volume rises in hot, humid months and drops off in winter. A storage container sized for a typical week evens out both patterns without needing to be emptied constantly.
Why this matters beyond one household
Neither RO reject water nor AC condensate is a large volume on its own, which is part of why both get ignored. But both appliances are common — most urban homes and nearly every office now run at least one of the two — and default waste from ordinary appliances, repeated across millions of households, adds up to real pressure on local water systems. Capturing it doesn't require a policy change or new infrastructure; it's a one-time fix at the appliance level that a household or business can make on its own.
How h2osave's kits handle this
Our AC Water Conservation Kit and RO Waste Water Conservation Kit are built around exactly this approach — a one-time installation that redirects each waste stream into storage for reuse, with no ongoing maintenance and no impact on the appliance itself. For a deeper look at each one individually, see our guides on RO reject water and AC condensate reuse.
Get in touch to see which kit fits your home or office.