Around 70% of what a Pakistani household drains is greywater, sink, shower and washing machine water that never touched sewage. It leaves the house clean enough to flush a toilet with.
One appliance-sized unit that sits where a washing machine sits, takes greywater in at the trap, and gives it back for flushing, gardening and laundry.
Pakistan crossed the water scarcity threshold years ago and is still falling. These numbers set both the case for the product and its size.
Estimates for urban households. Showers and sinks carry the volume; the washing machine is the easiest to plumb into.
I took four systems apart on paper: what they recover, what they cost landed, what they ask of the owner. The technology is settled; the access is not.
Everything effective sits above $4,000 and needs a professional install into pipes a renter does not own. Diverter valves at $50-200 move water but treat none of it. That gap is the brief: treatment at a domestic price, plumbed in without touching the wall.
Interviews across Karachi, Lahore, Islamabad and Peshawar, renters, owners, students. None owned the pipes they wanted to change.
What separated them was permission and skill, not willingness. It had to work for someone who cannot drill a wall and should not have to learn what an MBBR is.
Ideation ran in two passes. The first worked the system out: where greywater is collected, how filtration, storage and control stack, and what fits under a sink or beside a washing machine.
The second pass was form. Trolleys, backpacks, bins and appliance shapes against the same internal volume, until it settled on a fluted body on castors, domestic equipment, not plant machinery.
Greywater enters at the trap, drops its solids, then meets biofilm carriers that eat the organic load. Air flotation lifts the remaining soap and grease off the top.
The filter model adds a final physical stage; the filterless one relies on biology and flotation alone. Treated water waits in the tank until a toilet or tap asks for it.
Tested with simulated greywater from detergent and washing cycles.
The body is Alucobond, light, corrosion-proof, foldable on a press brake, which is what made a one-off prototype possible. Everything wet is HDPE or stainless.
Chambers stack on a stainless base plate with adjustable footings, so an uneven floor does not put the unit out of level.
The unit is sold against the fixture it sits next to, kitchen sink, washing machine or washroom. That decides the inlet, the footprint and the volume.
Each of the three comes filter-based or filterless. Filterless drops the final stage and the monthly cartridge with it, at some cost in efficiency.
Panels are CNC-cut and folded from Alucobond, chambers moulded HDPE, base frame laser-cut and MIG-welded. No process a Lahore workshop does not already run.
Assembly is six stages: base and footings, chambers, piping, electronics, casing, then a leak and power-up test.
I built the working prototype by hand in the last weeks: panels folded on the press brake, stainless frame welded, acrylic chambers bonded and pressure-checked.
The lab rig at IESE gave the media a reference to work against. Everything else came from hardware shops, submersible pump, push-fit connectors, a ball valve.
Appliance proportions on purpose, the unit is meant to read as a thing that belongs next to a washing machine, not as equipment.
Installation is four levelling footings, an inlet and an outlet. Filters are cleaned monthly; sensors self-calibrate, and an alert light handles clogs and overflow.
On the bill, that is roughly a quarter off an urban household’s water cost, with payback in three to five years, the number that decides whether any of this gets bought. The project sits against SDG 6 and SDG 9.
