View Full Version : High TDS

07/01/2015, 08:17 PM
I've replaced all my filters and my DI resin. My RO/DI is about a year old.

After I run the RO/DI for a while all is good, but if I try to start the RO/DI again the next day, the Tds spikes up to over 300 or more and it takes over a half hour to get it down to 3.

Is this normal? Anything I should do differently?

I actually start the RO and let it run down to 2 or less before I put the water through the DI resin.

07/02/2015, 10:21 AM
Spikes like that are inevitable, although 30 minutes is a long time. How long does it take to get down to, say, 10 TDS? There may be diminishing returns on waiting for perfection.

As an example, say you get to 10 TDS in 15 minutes. Another 15 minutes of 10 TDS (and then less) is a gallon produced: that's a less than 10-ppm-gallon load on a DI cart that can handle 6000-ppm-gallons.

Try flushing the RO membrane AFTER using it, as that will reduce the concentrated waste water in the housing that you are seeing on start-up.