Here is an old picture of mine. It has since been converted to a dual membrane 240 GPD system.
I have a Sears 32,000 grain water softener in the beginning.
Next is:
1. 0.2 micron ZetaZorb absolute rated pleated prefilter with 10x the surface area of a normal poly prefilter.
2. 0.5 micron Chlorine Guzzler 20,000 gallon carbon block
3. 90 GPD Select Series hand tested 98+% rejection rate RO membrane.
4. 150 GPD Select Series hand tested 98+% rejectoion rate RO membrane.
5. MaxCap DI Cartridge
6. SilicaBuster DI Cartridge
I have a 14 gallon pressure/bladder tank that stores RO only water which is used for drinking, icemaker, cooking and other home uses and also feeds back to the Dual DI system for reef water. Everything is mounted in my garage which is attached to my house andclimate controlled.
Tap water TDS averages 835, RO only TDS averages 5.3 to 6.2 and DI water stays at a true 18.2 megaohms or much less than an indicated 0 TDS for about 630 gallons per MaxCap cartridge. This is a big improvement over the 150 gallons I used to get with a normal 75 GPD Dow Filmtec RO membrane and fresh bulk DI resin. Even though the MaxCap unit comes with 2 dual inline TDS meters I use a HM Digital COM-100 handheld calibrated so it is very accurate at the low end for DI water. I have confirmed these readings with a Thornton benchtop conductivity/resistivity meter.
Inline TDS meters should be used as a guide only as they are not nearly as accurate as a handheld meter since they are not temperature compensated.
corals B 4 bills, you have several cartridges that really serve no purpose and can cut the number in half and still get just as good of water. All the prefilter and carbon block are for is to protect the RO membrane, well the carbon does also remove some volatile organics which helps the membrane and DI out a little, but you don't need nearly that many cartridges or canisters. They have almost no effect on TDS whatsoever as its the job of the RO membrane and DI resin to remove TDS. The very first prefilter should remove any TSS or suspended solids which are much larger than TDS.