Total Dissolved Solids (TDS)

[Davidfrances]

Would anyone know what the TDS measurements should be for reverse osmosis water? My new unit is delivering water with a TDS reading of 20 ppm(?), and my tap water is reading 22 ppm.

 

[CBRGuy]

that's about right for RO water. DI would give you about 0 - 3 TDS

 

[Atari]

Your tap water is only 22? Wow..

You should be getting closer to zero with a new unit so somethings not right. Does it have a DI cart?

 

[Davidfrances]

I ran a test with distilled water, which gave a reading of 1ppm, Then I tested my tap water, and the reading was 22ppm. I then retested my ro product water, and obtained a reading of 54ppm, and my ro waste water is 65ppm. I've only run about 10 gallons of product water throught the unit, which does have a DI cartridge. Is there a break in period? th manufacturer is Aquasafe from Canada. My TDS tester is a milwaukee unit.

 

[loganj]

Are you sure the RO membrane is correctly installed? If your tap water is 22, I fail to see how it's possible for the RO to be 54 and the waste to be 65...not saying you're wrong...it just doesn't make sense. Your end product should have a TDS of 0. RO membranes are packed in fluid that needs to be flushed out before the unit is put into regular service. Did you flush the system before adding the DI? If not, you may have contaminated the DI cartridge. I would check installation of the RO membrane (make sure it's not in backwards), then check the TDS of the water coming from the RO membrane. I would think, with a tap water reading of 22, that your RO should deliver 10-12 ppm water. The DI should take it to 0. If it doesn't, you may need to replace the DI. JMHO.

 

[seaham358]

I have a ro/di and my membrane did not come packed in water and neither did the new replacement membrane and my water is at 0 TDS..... And flush system before adding Di unit is another statement that throws me??? Flush the whole system before using the water in your tank yes...... Flush the system after you change filters.....Yes..
You keep saying ro water are you sure you have a DI as the last cartridge???
There should be a sediment filter then a carbon filter then a DI unless your running 2 Carbons. And the Membrane is in before the DI cartride.
Your lucky to have water at 22 TDS....... I know a guy who is around 700 TDS Im at 180 before the filters...
I would check the lines to make sure there in proper order......

 

[MantisFreak]

You are supposed to use a backflush kit with a brand new membrane. If you don't have a backflush kit, you are not supposed to use the first 10 to 20 gallons of water. A preservative and anti-bacterial agents were on your membrane and they are showing up as higher than normal TDS. Once the membrane is flushed, you will probably go down to zero.

 

[darb2]

my tap water tests at 70
after a ro only it is 15-17
make sure you rinse the test container thouroughly as it can throw the reuslts off. Also if you dont have a top on the bucket you collect ro water in it can pick up contaminents from the air

 

[Davidfrances]

The unit I purchased is a 75 gpd unit. I ran it for several hours straight, and TDS readings are now down to 1 to 2 ppm (down from 54 ppm). I expect them to continue falling as the unit breaks in. Thanks for everyone's advice!