Did it start lower? Most DI units should give 0-1 ppm when workign well, as as the TDS rises when the get shot, things go bad fast.
You might check this article:
What is TDS?
http://www.reefkeeping.com/issues/20...ture/index.htm
from it:
"7. If you are using a TDS or conductivity meter to monitor the performance of an RO membrane, then the measured value should drop by at least a factor of 10 from the starting tap water. So, for example, if the tap water reads 231 ppm, then the RO water should be less than 23 ppm. In many cases, it will drop much more than that. Less of a drop than a factor of 10 indicates a problem with the RO membrane.
8. If you are using a TDS or conductivity meter to monitor the performance of an RO/DI system, then the measured value should drop to near zero. Maybe 0-1 ppm. Higher values indicate that something is not functioning properly, or that the DI resin is becoming saturated and needs replacement. However, that does not necessarily mean that 2 ppm water is not OK to use. But beware that it may begin to rise fairly sharply when the resin becomes saturated. Do not agonize over 1 ppm vs. zero ppm. While pure water has a TDS well below 1 ppm, uncertainties from carbon dioxide in the air (which gets into the water and ionizes to provide some conductivity) and the TDS meter itself may yield results of 1 or 2 ppm even from pure water. "