Conductivity anomalies in DM plant in Tarapur, Maharashtra - Need reason for the phenonmenon

I am Working as a Plant Incharge in Tarapur Atomic Power Station as a Plant In-charge of DM Plant for the Past 10 Months. Here we are getting SBA O/L Conductivity is less and MB O/L Conductivity is high.What are the Causes for this?

Details  : 30m3/hr Auto DM Plant consists of Contact Tank,SAC,Degasser, SBA and MB

Fresh Water I/L Conductivity - 180 microsiemens / Cm
SAC O/L Conductivity          -   140-150 microsiemens
What could be the reason for this phenomenon?

C.Sankar anand