RO topoff & TDS creep

[Railskinner]

I also have the same problem with the first water at reading being around 50's. I think this is the water that sits in the RO unit for awhile. Then the water levels out with a lower reading when ran for a minute.This is what goes into my container, test the water in my container and it reads 5ppm. This is the water that goes into sump.I can live with that.

[Dave C]

I agree. But when my float switch drops & the RO starts it doesn't run for a minute. It stops well before that. So it never gets to the point where the water tds levels out with a lower reading. It also is supposed to deplete your DI resin much faster to be intermittently starting & stopping your RO unit. Much better to run it for 5 gallons & stop it.