[landy2]

when you fill up your tank by ro unit why do you have to have waste water

[jonisondell]

that is a very good question

[NWH]

when you fill up your tank by ro unit why do you have to have waste water

I thought you`d know that Mark.

[michael papworth]

This isn't an exact scientific description!

The RO unit pushes water molecules through a membrane and doesn't allow the larger dissolved solids molecules to pass. You need the waste water to flush the excess dissolved solids away.

To convince yourself that this is exactly what happens, take three TDS reading of:

Regular tap water (probably a couple of hundred or so)
RO output water (should be very low - between 002 and 010)
RO waste water (considerably higher than regular tap water)

That shows you what happens.

[R W C]

Hello wally where you been

[Neil Williams]

Think of it like fuel in a car.
The engine burns what can be burnt to produce the power then the exhaust pushes out the waste.
I remember a question on a Physics exam which was why isn't any machine 100% efficient? The answer is because there is waste.