>Typical reverse osmosis filters produce one unit of clean water for every three units of intake
That's actually a very optimistic figure IME:
I recently started using a consumer under-sink RO system from GE Appliances at my off-grid cabin, the kind you find at Home Depot.
If you use the included pressurized accumulator tank, the stated efficiency is ~10%.
Since I'm off-grid, the reject line is run to a 5-gallon water cooler bottle, making product:reject water ratio comparisons trivial. Even 10% is somewhat optimistic.
The efficiency is about double if you disable the pressurized accumulator, that way there's no pressure on the other side of the membrane (except when stopped). It's not a simple fixed ratio since the efficiency decreases as the accumulator fills and the pressure difference across the membrane approaches zero. It's actually pretty insane how wasteful the system is as-delivered if you use the accumulator, towards 100% full it's mostly just rejecting water for an hour+.
Without the accumulator, but using the included reject water restriction orifice, it's more like 20-25%. I've ended up adding an adjustable restrictor valve on the reject water line to keep it closer to the 3:1 you described, which shouldn't damage the membrane AIUI.
I guess it's just safe defaults they ship in an unsophisticated system connecting to potentially high inlet pressures. This combined with a luxurious pressurized accumulator tank, makes it spectacularly wasteful of perfectly good water. Most wouldn't even realize the waste volumes having the reject line plumbed into the sink drain.
I've been making huge hexagonal concrete pavers with the reject water...
That's actually a very optimistic figure IME:
I recently started using a consumer under-sink RO system from GE Appliances at my off-grid cabin, the kind you find at Home Depot.
If you use the included pressurized accumulator tank, the stated efficiency is ~10%.
Since I'm off-grid, the reject line is run to a 5-gallon water cooler bottle, making product:reject water ratio comparisons trivial. Even 10% is somewhat optimistic.
The efficiency is about double if you disable the pressurized accumulator, that way there's no pressure on the other side of the membrane (except when stopped). It's not a simple fixed ratio since the efficiency decreases as the accumulator fills and the pressure difference across the membrane approaches zero. It's actually pretty insane how wasteful the system is as-delivered if you use the accumulator, towards 100% full it's mostly just rejecting water for an hour+.
Without the accumulator, but using the included reject water restriction orifice, it's more like 20-25%. I've ended up adding an adjustable restrictor valve on the reject water line to keep it closer to the 3:1 you described, which shouldn't damage the membrane AIUI.
I guess it's just safe defaults they ship in an unsophisticated system connecting to potentially high inlet pressures. This combined with a luxurious pressurized accumulator tank, makes it spectacularly wasteful of perfectly good water. Most wouldn't even realize the waste volumes having the reject line plumbed into the sink drain.
I've been making huge hexagonal concrete pavers with the reject water...