RO/DI water testing

[saltwatercowby]

I got a new RO/DI filter system in. How do i check to make sure it is pure water? I'm sure it is working fine but would like to make sure, plus i would like to know when the filters get spent?

 

[veni vidi vici]

TDS Meter

 

[bulldog123]

TDS meter inline or hand held.

 

[saltwatercowby]

Thank you