High TDS presence in water

The reason for high TDS may be inaccurately flushed RO membrane. New RO membrane needs to be flushed immediately after installation. In order to thoroughly flush the membrane fill the whole tank (12 liters/3.2 gallons), then empty the tank completely. Repeat it at least once. 

WARNING! Do not drink the first two parts of water.

Another reason, the membrane may be installed incorrectly inside of the membrane housing. Remove the membrane from the housing, check for damaged o-rings: at the top and two o-rings on the bottom. O-rings should be re-greased with petroleum jelly and installed again inside the housing.