110g Mixed Reef V2

[Delphinus]

THAT's interesting (although I think it's technically a "loo" believe it or not). Anyhow of course what happens when that happens is there will be a dip in pressure in your lines but I wouldn't have guessed it would cause TDS to dip as well. I've never tried measuring TDS on the inlet side of my RO/DI so I can't try this myself. I have my "inlet" side after the RO, and my "outlet" side after the DI. So I have no idea what the incoming TDS is (I just know it sucks like 150-250), but the nice thing about setting it up this way is that I can tell when it's time to change the RO membrane and I can tell when it's time to change the DI (even though the colour change ought to be good enough for that I suppose). Also I know when it's OK to stop flushing the membrane (post-RO reading starts off at 90ish usually, and I switch the flush valve over when it drops below 10. It takes a lot longer than I thought it would. Before I had one I would just flush the membrane for like 30 seconds to a minute, since getting the dual meter I learned it's more like 5 minutes minimum..).