RO/DI showing 3 after only about 200 total gallons made?


New member
I have a coralife 75gpd RO/DI and after only about 200 total gallons made it is starting to creep up from '0' to '3'....I realized my drip rate is wrong....what is the correct rate for waste water to good water?

Also, should a new sediment(which is brown now) be enough to get me back to 'o', or do you think a mixed "DI" is already needed as well? Or a sediment and carbon?

*I don't have a "t'd" line yet to test post RO before the DI.....Incoming TDS measures from 170-260


New member
You want a waste to good ratio between 4-6 to 1. So somewhere in that range. It is entirely possible after 200 gallons for the DI resin to be cached. It would not be good, but it would certainly be possible. I don't believe a sediment filter will help you much here but you should remember to change them out along with carbon filters every 6 months. It will help once you get your RO only line Teed off to determine what TDS water you are feeding to the DI.


In Memoriam
I used to get 150 gallons per 24 oz DI refill with my other unit which had a 75 GPD Dow Filmtec membrane and good quality pre and carbon filters. My tap water is in the 700s to 800s, RO only was 13 to 15 and RO/DI stayed at 0 for right at 150 gallons.
You really need the RO only number to judge how well your system is working, without that you are guessing as to efficiency. Unscrew the DI and take the cartridge out for a few minutes and see what you get. That or just unplug the 1/4" tube from the RO to the DI and measure there.
Waste ratio is normally 4:1 4 waste to 1 good, much less and you shorten the membrane life. Changing the sediment filter will; have no effect on TDS, its there to capture suspended solids not dissolved solids. Its a good idea to have a pressure gauge though or even two to monitor filter plugging if you think that may become a problem. I have one on the incoming line and one after the prefilter/carbon but before the RO so I can monitor filter conditions. I also monitor tap water, post carbon, post RO. post MaxCap DI and post Silica Buster DI so I know what each piece of the RO/DI system is doing. Its takes all the components to work correctly and last for any length of time.