The Food Control Department of Dubai Municipality is planning to increase the frequency of taking water samples from tanks after the cleaning process. The move is being contemplated with a view to checking the effectiveness of work done by water tank cleaning companies. The department may, at later stages, also start grading these cleaning companies, Gulf News has learnt. The work of cleaning water tanks is required to be done by companies that hold a valid licence from the municipality. Presently, the civic body takes random samples of water before and after the cleaning process. However, incidents of unclean tanks and contaminated water have been reported in the last few months. In many buildings water tanks were not being cleaned regularly, posing a danger to residents. Source of disease Bottled water is used for drinking in most households in Dubai, but many residents use tap water for cooking along with washing and cleaning. Contaminated water can cause various types of infections and is a potential source of many diseases. It is hoped more frequent checks will encourage people to have tanks cleaned properly and more often. \"We are planning to set up a system to take the samples very frequently and, if possible, before and after every cleaning. There are also plans to grade the water tank cleaning companies,\" said Shaima Mohammad Al Tunaiji, principle food studies and surveys officer from the Food Studies and Planning Section of Food Control Department at Dubai Municipality. This year four new companies were approved by the authorities to clean water tanks and presently there are more than 40 companies engaged in this work. The cleaning companies are required to be properly equipped, train their staff and follow the rules by the civic body. At the time of renewal of the licence, the cleaning supervisor may also be required to go for a verbal or a written assessment on the cleaning process. Sometimes, however, the companies may also be banned. The department also has the tentative cleaning schedule of companies which helps it check whether the cleaning process is being carried out according to the rules.