Does a DIs resin last longer if you run the water through it slowly? I am thinking of using running water through mini bore to my twin/triple DI set up. My local TDS is 240-310, but I can't use an RO because I live in a flat. With this kind of set up where the DIs change around; the first one becomes the second one etc how do you guys remember which is the first DI and which the second? Write on it in pencil? Also, I heard that cleaning to a TDS of 15 is fine. I also heard it depends on the area not just the TDS level. This affects what actually is in the total dissolved solids (TDS) I live in Poole/Bournemouth anyone know if this area is ok to clean at a TDS of 15?