Water Filtration System

TechWriter wrote:
The main drawback of RO systems is waste water. An RO filter will "reject" a lot of water. However, I just plumb the RO waste water back into my RV's water tank.

ToastHater wrote:
That's exactly what I was thinking. I'm just not sure if that will cause more damage in the long run. Running all of the waste through the system repeatedly. Causing the maintenance/replacement cycles to be more frequent.

Bumpyroad wrote:
recirculating waste (dirty) water back into the feed water system would make that water dirtier and dirtier wouldn't it? what does that do for efficiency.
bumpy

RO 101

The system I and other RVers have are under-the-sink RO units for drinking water. I've only heard from a few RVers who have "whole RV" RO systems in which ALL water going into the RV passes through an RO system. The latter is wasteful, slowwwwwwwwwww, and hardly suited to RVing, much less boondocking.

Anyway, about RO "waste" water, also called brine. First, before water from outside your RV hits an RO filter membrane, it first goes through one or more pre-filters -- typically, a sediment and a carbon block filter.

When an RO system filters water, it lowers the TDS (Total Dissolved Solid) levels. For example, my Arizona water has these TDS levels:

724 ppm - "Fresh" water (no filtering)
697 ppm - RO waste water (brine)
24 ppm - RO treated water (the stuff you drink)

Since I plumb my RO waste water back into my water tank, the tank would eventually reach a point where the RO filter wouldn't work anymore without flushing new water into the tank.

However, if you're concerned about RO waste water fouling your water tank, just put a diverter on the waste water line: one setting to water tank, one setting to the ground or another holding tank.

I've been running an under-the-sink RO unit for several years. While I don't boondock, the system works great. When not connected to an external water source, my RV's water pump forces water from the water tank through the RO membrane.