Why does BRS recommend this?
Using a RODI system without a TDS meter is like driving a car without a speedometer and gas gauge. At some point you will end up in trouble. With RODI systems it is TDS that you will want to monitor for performance and filter quality. By using a dual TDS meter it will allow you to see your TDS readings in two places. We will usually suggest putting one probe before the DI stage and one after the DI stage to show what your RO is producing for water quality and then how your DI is performing by removing all remaining TDS from the final product water.
The DM-1 Dual Inline TDS Meter from HM Digital is one of the most important reverse osmosis accessories. This tool monitors the TDS of your reverse osmosis system in two places and lets you know exactly how the system is performing.
BRS suggests: installing the dual TDS meter post membrane and post DI stage. These two readings will notify you when it's time to change the RO membrane and DI resin. This unit features a digital display and comes with two 1/4" GA Murdock Quick Connect Tee's with double o-rings to ensure a proper seal. As with all HM-Digital products, the DM-1 comes factory calibrated.
Replacement Battery Type - LR44G
This TDS meter uses an LR44G Battery.
These meters read from 0 ppm in increments of 1 ppm to 999 ppm. (9990 with calculation) This will not go be lower than 1 ppm measurements. Feel free to let us know if you have any further questions!
The TDS meters on the units do not need replacement. In many cases they will last the life of the unit. It very well be that CO2 or other elements are reducing the DI resin faster than any TDS. Feel free to let us know if you have any further questions!
My question is what is the best way to test ( Deionized Water) the meter and calibrate it if necessary?
We don;t recommend calibrating the units as we have not found them to be out of calibration since we have been using them. The calibration steps would also need to occur in a laboratory environment. If your TDS coming out of the membrane is in the 100's there is most likely an issue with the membrane, which possibly needs to be replaced or a bacterial bloom in the housing.
It sure is. It uses a pair of button batteries that can be replaced fairly easily.