Originally Posted by SCSInet
He's talking about drinking the rejection water from the membrane, which has not gone through the DI stage.
Keep in mind that the RODI reject water contains everything that was removed from the product water by the membrane. Just as an example, let's suppose that for every 2 gallons of water, 1 gallon or reject water and 1 gallon of product water is produced.
This means that that 1 gallon of reject water will be twice as filthy as the water coming in, since it contains the junk that was removed from the product water.
That said, humans have a much higher tolerance for dirty water than the tapwater usually is, so even in that extreme example, it shouldn't hurt you. But, why do it? IMO it's not going to have a big impact, because in most situations, you can never drink as much as you produce. Instead, use that water to water plants or the lawn.
You can't just put a valve on the reject water. The reject line has to be able to flow unobstructed. Instead, run the waste line outside (either horizontally or downhill from the membrane), and run it into a barrel or similar implement with a valve or something that you can use to fill a watering can, etc.
actually, the waste water comes out before it goes through the RO membrane. thus, it has gone through the carbon blocks and the micron. it contains much less junk per volume than my tap water does, and it tastes noticably better. you're right, in that the waste would have to run unobstructed, so it may not be possible.