Webmanny,
Here's a few important tips you need to know about RO/DI filters.
First, the IN probe is installed at the output of the RO membrane. This is to monitor the life of the membrane (Above 10 TDS indicates it's time to replace it). You may want to consider adding a pressure gauge as well (If the pressure drops out of the acceptable range, that may indicate it's time to replace it). The OUT probe is installed after the DI stage to monitor the effectiveness of the system as a whole and the final output water.
Also, you want a 1:4 ratio between RO/DI water and waste water. Fortunately you can just use all that waste water for your washing machine since that is where you're installing it. Therefore you won't have any waste.
While you're setting this up, now would be the time to install individual flush valves or one flush valve at stage one so you can flush each filter individually. Each filter needs to be flushed separately before using them together. If you hook up all the filters and run the system, each filter is going to flush into and contaminate the next, which will substantially shorten the life of the next filter in line.
So, you can solve this by installing one tee and two valves between each stage, which could make the setup more cumbersome or by installing one tee and two valves after stage one and flushing each filter individually. Tee off the output of stage one and then install a valve inline after it. This valve will divert the water to your flush line. Then install a valve to control the flush line. Obviously just use the wye valve you purchased to turn the water off between each flush. Put your GAC filter in stage one, close the inline valve and open the flush line valve to flush it, then just install it. Next put your carbon block in stage one, flush it then install it. Then put your sediment filter in stage one, flush it, leave it and then close the flush valve and open the inline valve. Finally, turn on the whole system to flush the DI resin. I would recommend flushing the water into a clear container so you can visually see that the output water is clear, especially with the GAC and carbon block as you want to insure there are no more carbon fines being released to damage the next stage.
This is the proper way to setup an RO/DI, including replacing the filters. Of course very few manufacturers or retailers will tell you this or provide instructions as they want you to burn through those filters faster so you will replace them.
Also, if you haven't bought it yet, you must get TDS calibration fluid. There is absolutely no way to tell if your TDS meter is correct without calibrating. Just like you wouldn't use an uncalibrated refractometer, the same holds true here.
Finally, you should get in the habit of disinfecting each filter housing when you replace your filters. A mild bleach wash and thorough rinse will do. Carbon is what removes chloramines (disinfectant) and therefore the water is now a perfect breeding ground for bacteria. But be absolutely certain you throughly rinse the housings as any bleach that reaches the membrane will ruin it. Again, just a mild bleach solution.
I hope this helps and now that's high quality H2O.
