Ion free pure RO/DI H2O and ohn meter

[africangrey]

I know a purified H2O has resistance of 18.2 mega ohm's, and the meter are often build in for high end industrial RO/DI system, such as the Millipore's Milli-Q system or Barnstead nanopure. but those thing cost 1 to 2 grants.
Would any of you reefer out there know how to measure the water resistance using a regular Ohm meter, can you provide some instruction? TDS meter isn't cutting it.

[AZDesertRat]

Get a HM Digital COM-100 handheld TDS/Conductivity meter.

http://www.tdsmeter.com/products/com100.html

They are like $49 and extremely accurate.
I know you can get them from Spectrapure, Buckeye Field Supply and Air Water & Ice and possibly some of the other RC sponsors too. I compared my COM-100 to a $2000 Thornton lab model benchtop conductivity/resistivity meter and was very impressed with the side by side results.