RO/DI water

In general (that is, with a new RO/DI filters) what does RODI water test like? Is GH and KH quite low? I have this vision that its pure H2O with no minerals or bicarbonate buffer!

I suspect it depends on the tap water hardness and buffer level going in, but with a good RODI filter how much is filtered out?

tia

 

It should test pure.

 

Exactly as tgood says...should test pure....that is, everything is removed from the water during the process and when tested with a TDS meter (total dissolved solids) should read zero.

 

Testing RO/DI for most things is hard since it has too few ions to test reliably and most test kits and meters will not work on ultrapure water.

This is why you test RO/DI cor conductivity of TDS as almost everything present in watre has an electrical conductivity associated with it so shows up as TDS. These are the only reliable tests.

A good RO/DI system will take tap water TDS from whatever it starts out to about 2-4% of that original TDS with the RO membrane only then down to 0 TDS with the DI. It does not matter what it starts out, it could be 100 or 1,500 TDS, its going to perform about the same.

 

cool, thanks for the replies. Of course now, do i need to supplement the KH and GH to my desired levels? I am hoping a simple solution of baking soda will increase my KH or maybe some crushed coral, and some sort of GH booster or is the water safe 'as is' for freswater fish?

thanks!

 

For freshwater or brackish fish you probably need to use a buffer with RO/DI or use plain RO not RO/DI.

 

thanks!