In northern Estonia, higher levels of Ra-226 and Ra-228 concentrations give rise to problems with water treatment plants (WTPs) using Cambrian-Vendian (Cm-V) aquifer. During water treatment processes, radionuclides accumulate in the filter material to a level where the material could be classified as a radioactive material. In order to understand the scope of the problem, a nation-wide survey was carried out among the Cm-V fed treatment plants. Filter material and water samples were collected from 18 Estonian WTPs to analyse the activity concentration of Ra-226 and Ra-228 in filter materials and also the radium treatment efficiency was determined. Sixteen WTPs exceeded the exemption levels of 1 kBq * kg-1 set by the EC directive 2013/59/Euratom. The quantity of filter material exceeding the exemption levels was approximately 300 tons, average concentrations values for Ra-226, Ra-228 and Th-228 were, accordingly, 7.6 kBq * kg-1, 8.0 kBq * kg-1 and 5.6 kBq * kg-1. That includes WTPs not designed for radium removal. The results suggest a need to investigate further NORM generation in WTPs, as uncontrollable disposal of NORM may occur.